Publications by year
In Press
Harrison XA, Donaldson L, Correa-Cano ME, Evans J, Fisher DN, Goodwin C, Robinson B, Hodgson DJ, Inger R (In Press). A brief introduction to mixed effects modelling and multi-model inference in ecology.
Abstract:
A brief introduction to mixed effects modelling and multi-model inference in ecology
The use of linear mixed effects models (LMMs) is increasingly common in the analysis of biological data. Whilst LMMs offer a flexible approach to modelling a broad range of data types, ecological data are often complex and require complex model structures, and the fitting and interpretation of such models is not always straightforward. The ability to achieve robust biological inference requires that practitioners know how and when to apply these tools. Here, we provide a general overview of current methods for the application of LMMs to biological data, and highlight the typical pitfalls that can be encountered in the statistical modelling process. We tackle several issues relating to the use of information theory and multi-model inference in ecology, and demonstrate the tendency for data dredging to lead to greatly inflated Type I error rate (false positives) and impaired inference. We offer practical solutions and direct the reader to key references that provide further technical detail for those seeking a deeper understanding. This overview should serve as a widely accessible code of best practice for applying LMMs to complex biological problems and model structures, and in doing so improve the robustness of conclusions drawn from studies investigating ecological and evolutionary questions.
Abstract.
Harrison XA, Donaldson L, Correa-Cano ME, Evans J, Fisher DN, Goodwin C, Robinson B, Hodgson DJ, Inger R (In Press). A brief introduction to mixed effects modelling and multi-model inference in ecology.
Abstract:
A brief introduction to mixed effects modelling and multi-model inference in ecology
The use of linear mixed effects models (LMMs) is increasingly common in the analysis of biological data. Whilst LMMs offer a flexible approach to modelling a broad range of data types, ecological data are often complex and require complex model structures, and the fitting and interpretation of such models is not always straightforward. The ability to achieve robust biological inference requires that practitioners know how and when to apply these tools. Here, we provide a general overview of current methods for the application of LMMs to biological data, and highlight the typical pitfalls that can be encountered in the statistical modelling process. We tackle several issues relating to the use of information theory and multi-model inference in ecology, and demonstrate the tendency for data dredging to lead to greatly inflated Type I error rate (false positives) and impaired inference. We offer practical solutions and direct the reader to key references that provide further technical detail for those seeking a deeper understanding. This overview should serve as a widely accessible code of best practice for applying LMMs to complex biological problems and model structures, and in doing so improve the robustness of conclusions drawn from studies investigating ecological and evolutionary questions.
Abstract.
Harrison XA, Donaldson L, Correa-Cano ME, Evans J, Fisher DN, Goodwin C, Robinson B, Hodgson DJ, Inger R (In Press). Best practice in mixed effects modelling and multi-model inference in ecology.
Abstract:
Best practice in mixed effects modelling and multi-model inference in ecology
The use of linear mixed effects models (LMMs) is increasingly common in the analysis of biological data. Whilst LMMs offer a flexible approach to modelling a broad range of data types, ecological data are often complex and require complex model structures, and the fitting and interpretation of such models is not always straightforward. The ability to achieve robust biological inference requires that practitioners know how and when to apply these tools. Here, we provide a general overview of current methods for the application of LMMs to biological data, and highlight the typical pitfalls that can be encountered in the statistical modelling process. We tackle several issues relating to the use of information theory and multi-model inference in ecology, and demonstrate the tendency for data dredging to lead to greatly inflated Type I error rate (false positives) and impaired inference. We offer practical solutions and direct the reader to key references that provide further technical detail for those seeking a deeper understanding. This overview should serve as a widely accessible code of best practice for applying LMMs to complex biological problems and model structures, and in doing so improve the robustness of conclusions drawn from studies investigating ecological and evolutionary questions.
Abstract.
Hosken DJ (In Press). Beware the F-test (or, how to compare variances). Animal Behaviour
Salguero Gomez R, Jones O, Archer R, Bein C, de Burh H, Farack C, Gottschalk F, Hartmann A, Henning A, Hoppe G, et al (In Press). COMADRE: a global database of animal demography.
Abstract:
COMADRE: a global database of animal demography
1. The open-access scientific philosophy has been widely adopted and proven to promote considerable progress in the fields of ecology and evolution. Open-access global databases now exist on animal migration, the distribution of species, and conservation status, to mention a few. However, a gap exists for databases on population dynamics spanning the rich diversity of the animal kingdom. This information is fundamental to our understanding of the conditions that have shaped variation in animal life histories and their relationships with the environment. Furthermore, an animal population schedules of reproduction and mortality determine its invasive potential, and its risk of local extinction, which are at the core of conservation biology. 2. Matrix population models (MPMs) are among the most widely used demographic tools by animal ecologists. MPMs project population dynamics in terms of reproduction, mortality, and development over the entire life cycle. The results of MPMs have direct biological interpretations, facilitating comparisons among animal species as different as Caenorhabditis elegans, Loxodonta africana and Homo sapiens. 3. Thousand of animal demographic records exist in the form of MPMs, but they are dispersed throughout the literature, rendering comparative analyses difficult. Here, we introduce the COMADRE Animal Matrix Database version 1.0.0, an open-source online repository containing data on 402 species worldwide, from 272 studies, with a total of 1,575 population projection matrices. COMADRE also contains ancillary information (e.g. ecoregion, taxonomy, biogeography, etc.) that facilitates interpretation of the numerous demographic metrics that can be derived from its MPMs. 4. Synthesis: We introduce the COMADRE Animal Matrix Database, a resource for animal demography. The open access nature of this database, together with its ancillary information will facilitate comparative analysis, as will the growing availability of databases focusing on other traits, and tools to query and combine them. Through future frequent updates of COMADRE, and its integration with other online resources, we encourage animal ecologists to tackle global ecological and evolutionary questions with unprecedented statistical power.
Abstract.
Silk M, Weber NL, Steward LC, Hodgson D, Boots M, Croft DP, Delahay RJ, McDonald R (In Press). Contact networks structured by sex underpin sex-specific epidemiology of infection. Ecology Letters
Hodgson D, Jelbert K, Buss D, McDonald J, Townley S, Franco M, Stott I, Jones O, Salguero Gomez R, Buckley Y, et al (In Press). Demographic amplification is a predictor of invasiveness among plants.
Nature CommunicationsAbstract:
Demographic amplification is a predictor of invasiveness among plants
Invasive plant species threaten native biodiversity, ecosystems, agriculture, industry and human health worldwide, lending urgency to the search for predictors of plant invasiveness outside native ranges. There is much conflicting evidence about which plant characteristics best predict invasiveness. Here we use a global demographic survey for over 700 plant species to show that populations of invasive plants have better potential to recover from disturbance than non-invasives, even when measured in the native range. Invasives have high stable population growth rates in their invaded ranges, but this metric cannot be predicted based on measurements in the native ranges. Recovery from demographic disturbance is a measure of transient population amplification, linked to high levels of reproduction, and shows phylogenetic signal. Our results demonstrate that transient population dynamics and reproductive capacity can help to predict invasiveness across the plant kingdom, and should guide international policy on trade and movement of plants.
Abstract.
Silk MJ, Hodgson D, Rozins C, Croft D, Delahay R, Boots M, McDonald R (In Press). Integrating social behaviour, demography and disease dynamics in network models: applications to disease management in declining wildlife populations. Philosophical Transactions B: Biological Sciences
Wigmore, C. Hodgson, D.J. Wedell, N. (In Press). Multiple mating increases female fitness in <em>Drosophila simulans</em>. Animal Behaviour
Silk MJ, Drewe JA, Delahay RJ, Weber N, Steward LC, Wilson-Aggarwal J, Boots M, Hodgson DJ, Croft DP, McDonald RA, et al (In Press). Quantifying direct and indirect contacts for the potential transmission of infection between species using a multilayer contact network. Behaviour
Silk MJ, Webber N, Steward LC, Delahay RJ, Croft DP, Hodgson, Hodgson DJ, Boots M, McDonald RA (In Press). Seasonal variation in daily patterns of social contacts in the European badger Meles meles. Ecology and Evolution
Silk MJ, Croft DP, Delahay RJ, Hodgson DJ, Boots M, Weber N, McDonald RA (In Press). Using social network metrics in wildlife disease ecology, epidemiology and management. Bioscience
2023
Gascoigne SJL, Rolph S, Sankey D, Nidadavolu N, Picman ASS, Hernandez CM, Philpott MER, Salam A, Bernard C, Fenollosa E, et al (2023). A standard protocol to report discrete stage-structured demographic information.
METHODS IN ECOLOGY AND EVOLUTION,
14(8), 2065-2083.
Author URL.
Soriano-Redondo A, Inger R, Sherley RB, Rees EC, Abadi F, McElwaine G, Colhoun K, Einarsson O, Thorstensen S, Newth J, et al (2023). Demographic rates reveal the benefits of protected areas in a long-lived migratory bird.
Proceedings of the National Academy of Sciences,
120(12).
Abstract:
Demographic rates reveal the benefits of protected areas in a long-lived migratory bird
. Recent studies have suggested that protected areas often fail to conserve target species. However, the efficacy of terrestrial protected areas is difficult to measure, especially for highly vagile species like migratory birds that may move between protected and unprotected areas throughout their lives. Here, we use a 30-y dataset of detailed demographic data from a migratory waterbird, the Whooper swan (
. Cygnus cygnus
. ), to assess the value of nature reserves (NRs). We assess how demographic rates vary at sites with varying levels of protection and how they are influenced by movements between sites. Swans had a lower breeding probability when wintering inside NRs than outside but better survival for all age classes, generating a 30-fold higher annual growth rate within NRs. There was also a net movement of individuals from NRs to non-NRs. By combining these demographic rates and estimates of movement (into and out of NRs) into population projection models, we show that the NRs should help to double the population of swans wintering in the United Kingdom by 2030. These results highlight the major effect that spatial management can have on species conservation, even when the areas protected are relatively small and only used during short periods of the life cycle.
.
Abstract.
Pincheira-Donoso D, Harvey LP, Johnson JV, Hudson D, Finn C, Goodyear LEB, Guirguis J, Hyland EM, Hodgson DJ (2023). Genome size does not influence extinction risk in the world's amphibians.
FUNCTIONAL ECOLOGY,
37(1), 190-200.
Author URL.
Hudson DW, Hodgson DJ, Cant MA, Thompson FJ, Delahay R, McDonald RA, McKinley TJ (2023). Importance sampling and Bayesian model comparison in ecology and evolution.
Methods in Ecology and EvolutionAbstract:
Importance sampling and Bayesian model comparison in ecology and evolution
Bayesian approaches to the modelling of ecological systems are increasingly popular, but there are competing methods for formal model comparisons. Here, we focus on the task of performing multimodel inference through estimating posterior model weights, which encompasses uncertainties in the choice of competing model structure into the inference outputs. Model-based approaches such as reversible-jump Markov chain Monte Carlo (RJ-MCMC) are flexible and allow multimodel inference, but can be complex to implement and optimise, and so we translate a model-based approach for ecological applications using Importance Sampling to estimate the marginal likelihood of the data given a particular model. This approach allows for model comparison through the estimation of Bayes' Factors or interpretable posterior model probabilities, yielding model weights that facilitate multimodel inference through Bayesian model averaging. We demonstrate Importance Sampling with two case study investigations in animal demography: censused analysis of banded mongoose (Mungos mungo) survival where missing data are uncommon, and capture–mark–recapture analysis of European badger (Meles meles) survival where data are commonly missing. We compare outcomes of the model comparison using the Importance Sampling approach to those obtained through single-model inference approaches using Deviance information criteria and the Watanabe–Akaike information criteria. The results of the Importance Sampling method aligns with RJ-MCMC model comparisons while often being more straightforward to fit and optimise, particularly if the competing models are non-nested.
Abstract.
Hudson DW, McKinley TJ, Benton CH, Delahay R, McDonald RA, Hodgson DJ (2023). Multi‐locus homozygosity promotes actuarial senescence in a wild mammal.
Journal of Animal Ecology,
92(9), 1881-1892.
Abstract:
Multi‐locus homozygosity promotes actuarial senescence in a wild mammal
Abstract
Genome‐wide homozygosity, caused for example by inbreeding, is expected to have deleterious effects on survival and/or reproduction. Evolutionary theory predicts that any fitness costs are likely to be detected in late life because natural selection will filter out negative impacts on younger individuals with greater reproductive value.
Here we infer associations between multi‐locus homozygosity (MLH), sex, disease and age‐dependent mortality risks using Bayesian analysis of the life histories of wild European badgers Meles meles in a population naturally infected with Mycobacterium bovis (the causative agent of bovine tuberculosis [bTB]).
We find important effects of MLH on all parameters of the Gompertz–Makeham mortality hazard function, but particularly in later life.
Our findings confirm the predicted association between genomic homozygosity and actuarial senescence. Increased homozygosity is particularly associated with an earlier onset, and greater rates of actuarial senescence, regardless of sex. The association between homozygosity and actuarial senescence is further amplified among badgers putatively infected with bTB.
These results recommend further investigation into the ecological and behavioural processes that result in genome‐wide homozygosity, and focused work on whether homozygosity is harmful or beneficial during early life‐stages.
Abstract.
Marino F, Crowley SL, Williams Foley NA, McDonald RA, Hodgson DJ (2023). Stakeholder discourse coalitions and polarisation in the hen harrier conservation debate in news media.
People and Nature,
5(2), 668-683.
Abstract:
Stakeholder discourse coalitions and polarisation in the hen harrier conservation debate in news media
Abstract
Conservation conflicts are complex and can be deep‐rooted, with stakeholders holding entrenched policy positions. The actors involved producing verbal interconnected interactions that form policy debates. Thus, conservation debates can be viewed as network phenomena with stakeholders forming coalitions in support of, or opposition to, certain policies and practices.
We used Discourse Network Analysis of print media to investigate the structure and dynamics of the stakeholder debate around the management of hen harriers Circus cyaneus, a bird of prey at the centre of a long‐standing conservation conflict in the United Kingdom.
We aimed to determine whether the structure of discourse coalitions changed among the diverse aspects of the debate and whether the polarisation of the debate has changed through time. Our search and selection criteria led to the analysis of 737 statements within 131 newspaper articles published from August 1993 to December 2019.
We show that, while the discourse network of the overall debate is quite unstructured, actors formed divergent coalitions when defining the conservation problem and its solutions. In contrast, discourses converged around reactions with positive or negative emotions in relation to events and issues of hen harrier conservation. Polarisation among actors has increased over time and peaked in the second half of the 2010s, concurrent with the release of the species recovery plan.
Our study highlights the value of analysing discourse networks in conservation policy debates. Discourse networks reveal which aspects of any conservation problem cause stakeholders to converge or diverge and can identify periods of intensified debate that, ultimately, contribute to informing conflict mitigation and resolution processes.
Read the free Plain Language Summary for this article on the Journal blog.
Abstract.
2022
Weegman MD, Walsh AJ, Ogilvie MA, Bearhop S, Hilton GM, Hodgson DJ, Fox AD (2022). Adult survival and per-capita production of young explain dynamics of a long-lived goose population.
IBIS,
164(2), 574-580.
Author URL.
Clements SJ, Zhao Q, Silk MJ, Hodgson DJ, Weegman MD (2022). Modelling associations between animal social structure and demography. Animal Behaviour, 188, 51-63.
2021
McDonald JL, Hodgson D (2021). Counting Cats: the integration of expert and citizen science data for unbiased inference of population abundance.
ECOLOGY AND EVOLUTION,
11(9), 4325-4338.
Author URL.
Silk MJ, Hodgson DJ (2021). Differentiated Social Relationships and the Pace-of-Life-History.
Trends Ecol Evol,
36(6), 498-506.
Abstract:
Differentiated Social Relationships and the Pace-of-Life-History.
When selection is imposed by both social and ecological environments, the costs and benefits of social relationships can depend on life-history strategy. We argue that the formation and maintenance of differentiated social relationships will prevail in species and individuals with slow life histories. Social behaviours that benefit survival can promote slower life histories. Meanwhile, longer lifespan promotes the development of strong and stable social bonds by allowing fitness payoffs to be postponed. Differentiated social behaviours should be favoured for fast life histories only when they promote the rate of reproduction. Finally, associations between life-history strategies and other traits (e.g. personality) provide a mechanism to drive inter-individual variation in social relationships, making life-history important for sociality across taxonomic scales.
Abstract.
Author URL.
Evans JC, Hodgson DJ, Boogert NJ, Silk MJ (2021). Group size and modularity interact to shape the spread of infection and information through animal societies.
Abstract:
Group size and modularity interact to shape the spread of infection and information through animal societies
AbstractSocial interactions between animals can provide many benefits, including the ability to gain useful environmental information through social learning. However, these social contacts can also facilitate the transmission of infectious diseases through a population. Animals engaging in social interactions must therefore face a trade-off between the potential informational benefits and the risk of acquiring disease. In order to understand how this trade-off can influence animal sociality, it is necessary to quantify the effects of different social structures on individuals’ likelihood of acquiring information versus infection Theoretical models have suggested that modular social networks, associated with the formation of groups or sub-groups, can slow spread of infection by trapping it within particular groups. However these social structures will not necessarily impact the spread of information in the same way if its transmission is considered as a “complex contagion”, e.g. through individuals copying the majority (conformist learning). Here we use simulation models to demonstrate that modular networks can promote the spread of information relative to the spread of infection, but only when the network is fragmented and group sizes are small. We show that the difference in transmission between information and disease is maximised for more well-connected social networks when the likelihood of transmission is intermediate. Our results have important implications for understanding the selective pressures operating on the social structure of animal societies, revealing that highly fragmented networks such as those formed in fission-fusion social groups and multilevel societies can be effective in modulating the infection-information trade-off for individuals within them.Significance statementRisk of infection is commonly regarded as one of the costs of animal social behaviours, while the potential for acquiring useful information is seen as a benefit. Balancing this risk of infection with the potential to gain useful information is one of the key trade-offs facing animals that engage in social interactions. In order to better understand this trade-off, it is necessary to quantify how different social structures can promote access to useful information while minimising risk of infection. We used simulations of disease and information spread to examine how group sizes and social network fragmentation influences both these transmission processes. Our models find that more subdivided networks slow the spread of disease far more than infection, but only group sizes are small. Our results demonstrate that showing that fragmented social structures can be more effective in balancing the infection-information trade-off for individuals within them.
Abstract.
Evans JC, Hodgson DJ, Boogert NJ, Silk MJ (2021). Group size and modularity interact to shape the spread of infection and information through animal societies.
BEHAVIORAL ECOLOGY AND SOCIOBIOLOGY,
75(12).
Author URL.
Silk MJ, Hodgson DJ (2021). Life history and population regulation shape demographic competence and influence the maintenance of endemic disease.
Nat Ecol Evol,
5(1), 82-91.
Abstract:
Life history and population regulation shape demographic competence and influence the maintenance of endemic disease.
Host life history and demography play important roles in host-pathogen dynamics, by influencing the ability of hosts and their pathogens to coexist. We introduce the concept of demographic competence to describe the ability of host populations to sustain endemic infectious disease. Hosts with high demographic competence are more likely to act as keystone hosts and constitute reservoirs of infection that can spill over into other species. We propose that the pace of host life history will interact with pathogen life history to influence demographic competence. Our models demonstrate that slow-living hosts (with high survival and low recruitment rates) have greater demographic competence than fast-living hosts (with low survival and high recruitment rates) for susceptible-infected disease dynamics, although this difference is reduced when populations of slow hosts are age structured. Demographic competence is generally greater among hosts with populations regulated by survival compared to reproduction, but this difference is smallest among slow life histories and reversed for some pathogens with frequency-dependent transmission. An association between pathogen life history traits and the demographic competence of faster-living hosts also has implications for trade-offs between pathogen virulence and transmissibility. Overall, we demonstrate how host life history traits can help predict wildlife reservoirs of zoonoses and the vulnerability of populations to disease-induced extinction.
Abstract.
Author URL.
House CM, Lewis Z, Sharma MD, Hodgson DJ, Hunt J, Wedell N, Hosken DJ (2021). Sexual selection on the genital lobes of male Drosophila simulans.
Evolution,
75(2), 501-514.
Abstract:
Sexual selection on the genital lobes of male Drosophila simulans.
Sexual selection is thought to be responsible for the rapid divergent evolution of male genitalia with several studies detecting multivariate sexual selection on genital form. However, in most cases, selection is only estimated during a single episode of selection, which provides an incomplete view of net selection on genital traits. Here, we estimate the strength and form of multivariate selection on the genitalia arch of Drosophila simulans when mating occurs in the absence of a competitor and during sperm competition, in both sperm defence and offense roles (i.e. when mating first and last). We found that the strength of sexual selection on the genital arch was strongest during noncompetitive mating and weakest during sperm offense. However, the direction of selection was similar across selection episodes with no evidence for antagonistic selection. Overall, selection was not particularly strong despite genitals clearly evolving rapidly in this species.
Abstract.
Author URL.
Hesse E, O'Brien S, Lujan AM, Sanders D, Bayer F, Veen EM, Hodgson DJ, Buckling A (2021). Stress causes interspecific facilitation within a compost community.
ECOLOGY LETTERS,
24(10), 2169-2177.
Author URL.
Pincheira‐Donoso D, Harvey LP, Cotter SC, Stark G, Meiri S, Hodgson DJ (2021). The global macroecology of brood size in amphibians reveals a predisposition of low‐fecundity species to extinction.
Global Ecology and Biogeography,
30(6), 1299-1310.
Abstract:
The global macroecology of brood size in amphibians reveals a predisposition of low‐fecundity species to extinction
AbstractAimThe diversity of brood size across animal species exceeds the diversity of most other life‐history traits. In some environments, reproductive success increases with brood size, whereas in others it increases with smaller broods. The dominant hypothesis explaining such diversity predicts that selection on brood size varies along climatic gradients, creating latitudinal fecundity patterns. Another hypothesis predicts that diversity in fecundity arises among species adapted to different microhabitats within assemblages. A more recent hypothesis concerned with the consequences of these evolutionary processes in the era of anthropogenic environmental change predicts that low‐fecundity species might fail to recover from demographic collapses caused by rapid environmental alterations, making them more susceptible to extinctions. These hypotheses have been addressed predominantly in endotherms and only rarely in other taxa. Here, we address all three hypotheses in amphibians globally.LocationGlobal.Time periodPresent.Major taxa studiedClass Amphibia.MethodsUsing a dataset spanning 2,045 species from all three amphibian orders, we adopt multiple phylogenetic approaches to investigate the association between brood size and climatic, ecological and phenotypic predictors, and according to species conservation status.ResultsBrood size increases with latitude. This tendency is much stronger in frogs, where temperature seasonality is the dominant driver, whereas salamander fecundity increases towards regions with more constant rainfall. These relationships vary across continents but confirm seasonality as the key driver of fecundity. Ecologically, nesting sites predict brood size in frogs, but not in salamanders. Finally, we show that extinction risk increases consistently with decreasing fecundity across amphibians, whereas body size is a “by‐product” correlate of extinction, given its relationship with fecundity.Main conclusionsClimatic seasonality and microhabitats are primary drivers of fecundity evolution. Our finding that low fecundity increases extinction risk reinforces the need to refocus extinction hypotheses based on a suggested role for body size.
Abstract.
Pincheira-Donoso D, Harvey LP, Grattarola F, Jara M, Cotter SC, Tregenza T, Hodgson DJ (2021). The multiple origins of sexual size dimorphism in global amphibians.
Global Ecology and Biogeography,
30(2), 443-458.
Abstract:
The multiple origins of sexual size dimorphism in global amphibians
Aim: Body size explains most of the variation in fitness within animal populations and is therefore under constant selection from ecological and reproductive pressures, which often promote its evolution in sex-specific directions, leading to sexual size dimorphism (SSD). Several hypotheses have been proposed to explain the vast diversity of SSD across species. These hypotheses emphasize: (a) the mate competition benefits to larger male size (sexual selection); (b) the benefits of larger female size for fecundity (fecundity selection); (c) the simultaneous benefits of niche divergence for males and females to reduce intersexual competition for ecological resources (natural selection); and (d) the underlying impact of geographical variation in climatic pressures expected to shape large-scale patterns of SSD in synergy with the above selection pressures (e.g. intensification of fecundity selection as breeding seasons shorten). Based on a new, global-scale amphibian dataset, we address the shortage of large-scale, integrative tests of these four hypotheses. Location: Global. Time period: Extant. Major taxa studied: Class Amphibia. Methods: Using a > 3,500 species dataset spanning body size, ecological, life-history, geographical and climatic data, we performed phylogenetic linear models to address the sexual, fecundity, ecological and climatic hypotheses of SSD. Results: Evolution of SSD is discordant between anurans and salamanders. Anuran SSD is shaped by climate (male-biased SSD increases with temperature seasonality) and by nesting site. In salamanders, SSD converges across species that occupy the same types of microhabitats (“ecodimorphs”), whereas reproductive or climatic pressures have no effects on their SSD. These contrasts are associated with latitudinal gradients of SSD in anurans, but not in salamanders. Main conclusions: Amphibian SSD is driven by ecological and climatic pressures, whereas no roles for sexual or fecundity selection were detected. We show that macroevolutionary processes determined by different forms of selection lead to latitudinal patterns of trait diversity, and the lack of them.
Abstract.
2020
Silk MJ, McDonald RA, Delahay RJ, Padfield D, Hodgson DJ (2020). CMR<scp>net</scp>: an <scp>r</scp> package to derive networks of social interactions and movement from mark–recapture data.
Methods in Ecology and Evolution,
12(1), 70-75.
Abstract:
CMRnet: an r package to derive networks of social interactions and movement from mark–recapture data
Abstract
Long‐term capture–mark–recapture data provide valuable information on the movements of individuals between locations, and the contemporary and/or co‐located captures of individuals can be used to approximate the social structure of populations.
We introduce an r package (CMRnet) that generates social and movement networks from spatially explicit capture–mark–recapture data. It also provides functions for network and datastream permutations for these networks. Here we describe the package and key considerations for its application, providing two example case studies.
The conversion of spatially explicit mark–recapture data into social and movement networks will provide insights into the interplay between demography and behaviour in wild animal populations, with important applications in their management and conservation.
Abstract.
Che-Castaldo J, Jones OR, Kendall BE, Burns JH, Childs DZ, Ezard THG, Hernandez-Yanez H, Hodgson DJ, Jongejans E, Knight T, et al (2020). Comments to “Persistent problems in the construction of matrix population models”. Ecological Modelling, 416
Goodwin CED, Swan GJF, Hodgson DJ, Bailey S, Chanin P, McDonald RA (2020). Effects of food availability on the trophic niche of the hazel dormouse Muscardinus avellanarius.
Forest Ecology and Management,
470-471Abstract:
Effects of food availability on the trophic niche of the hazel dormouse Muscardinus avellanarius
The scale at which variations in food availability affect the foraging habits of individual animals can determine how the distribution of food resources affects populations. For species of conservation concern, these factors can have important implications for the management of habitats, as spatial and temporal variations in resource availability influence the trophic ecology of both individuals and populations. The hazel dormouse Muscardinus avellanarius is a species with seasonal dietary shifts and limited ranging, and whose populations in Great Britain are exhibiting marked decline, despite conservation measures. We compared resource availability and variation in dormouse traits with their trophic characteristics, determined by stable isotope analysis of dormouse hair and of their putative food items. The trophic levels of individual dormice were associated with the abundance of invertebrates in the surrounding habitat and in the woodland as a whole. Assessment of dormouse dietary composition suggests that the proportions of invertebrates and of tree seeds and flowers in dormouse diets are affected by the abundance of food plants in the local habitat. This suggests that dormice can exploit both invertebrates and plants in proportion to their availability, and are variable in their predatory habits, in response to both the availability of invertebrates and plants. Dormouse populations exhibit a broader trophic niche in autumn than in spring, most likely a consequence of their consumption of foods derived from a wider variety of tree and shrub species. We found no relationship between isotope signatures or food availability and the body mass or torpor of individuals, or the status of populations. This may be because, on the sites we studied, dormice could adapt to different food availabilities without discernible individual and population effects. Dormice are opportunistic feeders, rather than specialists, making use of abundant food resources at a local scale. Habitat conservation for dormice, therefore, could benefit from establishing and maintaining habitats that increase the overall abundance and uniform distribution of both flower and fruit-bearing shrubs and trees and invertebrate populations, at a fine spatial scale.
Abstract.
Bullock JM, Wichmann MC, Hails RS, Hodgson DJ, Alexander MJ, Morley K, Knopp T, Ridding LE, Hooftman DAP (2020). Human-mediated dispersal and disturbance shape the metapopulation dynamics of a long-lived herb.
Ecology,
101(8).
Abstract:
Human-mediated dispersal and disturbance shape the metapopulation dynamics of a long-lived herb.
As anthropogenic impacts on the natural world escalate, there is increasing interest in the role of humans in dispersing seeds. But the consequences of this Human-Mediated Dispersal (HMD) on plant spatial dynamics are little studied. In this paper, we ask how secondary dispersal by HMD affects the dynamics of a natural plant metapopulation. In addition to dispersal between patches, we suggest within-patch processes can be critical. To address this, we assess how variation in local population dynamics, caused by small-scale disturbances, affects metapopulation size. We created an empirically based model with stochastic population dynamics and dispersal among patches, which represented a real-world, cliff-top metapopulation of wild cabbage Brassica oleracea. We collected demographic data from multiple populations by tagging plants over eight years. We assessed seed survival, and establishment and survival of seedlings in intact vegetation vs. small disturbances. We modeled primary dispersal by wind using field data and used experimental data on secondary HMD by hikers. We monitored occupancy patterns over a 14-yr period in the real metapopulation. Disturbance had large effects on local population growth rates, by increasing seedling establishment and survival. This meant that the modeled metapopulation grew in size only when the area disturbed in each patch was above 35%. In these growing metapopulations, although only 0.2% of seeds underwent HMD, this greatly enhanced metapopulation growth rates. Similarly, HMD allowed more colonizations in declining metapopulations under low disturbance, and this slowed the rate of decline. The real metapopulation showed patterns of varying patch occupancy over the survey years, which were related to habitat quality, but also positively to human activity along the cliffs, hinting at beneficial effects of humans. These findings illustrate that realistic changes to dispersal or demography, specifically by humans, can have fundamental effects on the viability of a species at the landscape scale.
Abstract.
Author URL.
Evans JC, Silk MJ, Boogert NJ, Hodgson DJ (2020). Infected or informed? Social structure and the simultaneous transmission of information and infectious disease.
Oikos,
129(9), 1271-1288.
Abstract:
Infected or informed? Social structure and the simultaneous transmission of information and infectious disease
Social interactions present opportunities for both information and infection to spread through populations. Social learning is often proposed as a key benefit of sociality, while infectious disease spread are proposed as a major cost. Multiple empirical and theoretical studies have demonstrated the importance of social structure for the transmission of either information or harmful pathogens and parasites, but rarely in combination. We provide an overview of relevant empirical studies, discuss differences in the transmission processes of infection and information, and review how these processes have been modelled. Finally, we highlight ways in which animal social network structure and dynamics might mediate the tradeoff between the sharing of information and infection. We reveal how modular social network structures can promote the spread of information and mitigate against the spread of infection relative to other network structures. We discuss how the maintenance of long‐term social bonds, clustering of social contacts in time, and adaptive plasticity in behavioural interactions, all play important roles in influencing the transmission of information and infection. We provide novel hypotheses and suggest new directions for research that quantifies the transmission of information and infection simultaneously across different network structures to help tease apart their influence on the evolution of social behaviour.
Abstract.
Evans J, Silk M, Boogert N, Hodgson DJ (2020). Infected or informed? Social structure and the simultaneous transmission of information and infectious disease.
Soriano-Redondo A, Gutiérrez JS, Hodgson D, Bearhop S (2020). Migrant birds and mammals live faster than residents.
Nature Communications,
11(1).
Abstract:
Migrant birds and mammals live faster than residents
AbstractBillions of vertebrates migrate to and from their breeding grounds annually, exhibiting astonishing feats of endurance. Many such movements are energetically costly yet there is little consensus on whether or how such costs might influence schedules of survival and reproduction in migratory animals. Here we provide a global analysis of associations between migratory behaviour and vertebrate life histories. After controlling for latitudinal and evolutionary patterns, we find that migratory birds and mammals have faster paces of life than their non-migratory relatives. Among swimming and walking species, migrants tend to have larger body size, while among flying species, migrants are smaller. We discuss whether pace of life is a determinant, consequence, or adaptive outcome, of migration. Our findings have important implications for the understanding of the migratory phenomenon and will help predict the responses of bird and mammal species to environmental change.
Abstract.
Silk MJ, Harrison XA, Hodgson DJ (2020). Perils and pitfalls of mixed-effects regression models in biology.
PeerJ,
8, e9522-e9522.
Abstract:
Perils and pitfalls of mixed-effects regression models in biology
Biological systems, at all scales of organisation from nucleic acids to ecosystems, are inherently complex and variable. Biologists therefore use statistical analyses to detect signal among this systemic noise. Statistical models infer trends, find functional relationships and detect differences that exist among groups or are caused by experimental manipulations. They also use statistical relationships to help predict uncertain futures. All branches of the biological sciences now embrace the possibilities of mixed-effects modelling and its flexible toolkit for partitioning noise and signal. The mixed-effects model is not, however, a panacea for poor experimental design, and should be used with caution when inferring or deducing the importance of both fixed and random effects. Here we describe a selection of the perils and pitfalls that are widespread in the biological literature, but can be avoided by careful reflection, modelling and model-checking. We focus on situations where incautious modelling risks exposure to these pitfalls and the drawing of incorrect conclusions. Our stance is that statements of significance, information content or credibility all have their place in biological research, as long as these statements are cautious and well-informed by checks on the validity of assumptions. Our intention is to reveal potential perils and pitfalls in mixed model estimation so that researchers can use these powerful approaches with greater awareness and confidence. Our examples are ecological, but translate easily to all branches of biology.
Abstract.
Häkkinen H (2020). Unexplained limits on species distributions: how important is climate in defining species’ range edges?.
Abstract:
Unexplained limits on species distributions: how important is climate in defining species’ range edges?
The study of species’ range margins has a long history of academic interest, but is of particular relevance today due to its applications in modelling species range shifts induced by climate change, and predicting the spread of invasive species. Climate has long been assumed to structure species’ ranges over broad scales, but this consensus has recently been challenged by work on non-climatic factors, such as dispersal, biotic interactions and gene flow. It remains unclear how and where non-climatic factors can structure species’ ranges, and to what extent species’ ranges will consistently match sets of climatic conditions.
In this thesis I investigate what can lead to a species underfilling its climatic niche (when a species fails to colonise all climatically suitable areas), or expanding its climatic niche (when a species is able to colonise new types of climate). I find evidence that several non-climatic factors can slow or prevent non-native species colonising all climatically suitable areas in their naturalised regions, including dispersal, fragmentation of climatically suitable areas and the area of introduction. I also find that species will readily spread into new precipitation regimes with which they have not been previously associated. This suggests that species ranges can be constrained by non-climatic factors in the wettest part of their native range, and these constraints are frequently lifted in their naturalised range. I find evidence that species range limits set by temperature, in particular temperature maxima and minima, are more conserved and species will rarely expand into new thermal regimes. I also find evidence that species have different phenotypic responses to temperature across their range. Together these results indicate that a species’ current range frequently does not indicate its overall climatic tolerance, particularly in relation to precipitation, hence predictions that rely on associations between occurrence and environmental variables will frequently be flawed. Future work should consider a systematic way of detecting and including non-climatic factors that constrain the edges of species’ ranges.
Abstract.
2019
Hudson DW, Delahay R, McDonald RA, McKinley TJ, Hodgson DJ (2019). Analysis of Lifetime Mortality Trajectories in Wildlife Disease Research: BaSTA and Beyond.
DIVERSITY-BASEL,
11(10).
Author URL.
Pincheira-Donoso D, Meiri S, Jara M, Olalla-Tárraga MÁ, Hodgson DJ (2019). Global patterns of body size evolution are driven by precipitation in legless amphibians.
Ecography,
42(10), 1682-1690.
Abstract:
Global patterns of body size evolution are driven by precipitation in legless amphibians
Body size shapes ecological interactions across and within species, ultimately influencing the evolution of large-scale biodiversity patterns. Therefore, macroecological studies of body size provide a link between spatial variation in selection regimes and the evolution of animal assemblages through space. Multiple hypotheses have been formulated to explain the evolution of spatial gradients of animal body size, predominantly driven by thermal (Bergmann's rule), humidity (‘water conservation hypothesis’) and resource constraints (‘resource rule’, ‘seasonality rule’) on physiological homeostasis. However, while integrative tests of all four hypotheses combined are needed, the focus of such empirical efforts needs to move beyond the traditional endotherm–ectotherm dichotomy, to instead interrogate the role that variation in lifestyles within major lineages (e.g. classes) play in creating neglected scenarios of selection via analyses of largely overlooked environment–body size interactions. Here, we test all four rules above using a global database spanning 99% of modern species of an entire Order of legless, predominantly underground-dwelling amphibians (Gymnophiona, or caecilians). We found a consistent effect of increasing precipitation (and resource abundance) on body size reductions (supporting the water conservation hypothesis), while Bergmann's, the seasonality and resource rules are rejected. We argue that subterranean lifestyles minimize the effects of aboveground selection agents, making humidity a dominant selection pressure – aridity promotes larger body sizes that reduce risk of evaporative dehydration, while smaller sizes occur in wetter environments where dehydration constraints are relaxed. We discuss the links between these principles with the physiological constraints that may have influenced the tropically-restricted global radiation of caecilians.
Abstract.
Hodgson DJ, Lemaire G, Matthew C, Montossi F, Nan Z, Ren J, Da Silva S (2019). Just grazing the surface: a tribute to Professor John Hodgson 1937–2018.
Grass and Forage Science,
74(1), 2-5.
Abstract:
Just grazing the surface: a tribute to Professor John Hodgson 1937–2018
John Hodgson (1937–2018) is renowned worldwide as a passionate and principled researcher, dedicated to the study of interactions between grazing livestock and pasture sward, and to whole-system management of grassland. He published over 250 scientific outputs during his 50-year career, and inspired generations of grazing ecologists. Following his upbringing on a mixed-livestock farm in the Yorkshire Dales, John received BSc, PhD and DSc from the University of Leeds, UK. He worked in research institutes in Hurley, England and Penicuik, Scotland, before taking a Chair in Agronomy at Massey University, New Zealand in 1986. There, he progressed to become Head of School for the Environment. John retired from university life in 2002, but never left academia. John's global research legacy is reflected in the international authorship of this memorial review. His international impact is demonstrated by the supervision of over 50 PhD students from all over the world, and by his knowledge-sharing travels to South America and China. His peers will remember him as a thoughtful and collaborative scholar. His students will remember him as an inspiring and caring mentor. He helped to revolutionize the way that grasslands are managed, in the face of global environmental change and increasing demand on grazed systems. John lost a long battle with Parkinson's disease in October 2018 and is survived by his wife, Ruth, and five children. His own research was often dedicated to his father, Dick Hodgson, and the first author of this tribute wishes to do the same.
Abstract.
Ontiri EM, Odino M, Kasanga A, Kahumbu P, Robinson LW, Currie T, Hodgson DJ (2019). Maasai pastoralists kill lions in retaliation for depredation of livestock by lions.
People and Nature,
1(1), 59-69.
Abstract:
Maasai pastoralists kill lions in retaliation for depredation of livestock by lions
Abstract
The borders of national parks in Kenya are hotspots for human–wildlife conflict. The deliberate killing of lions by Maasai pastoralists is illegal, but continues despite mitigation attempts. Currently, there is a somewhat pervasive opinion, within the human–wildlife conflict literature, that lions are killed by Maasai people either as cultural ceremony or indiscriminately in response to the loss of livestock.
We reconsider the indiscriminate reputation of lion‐killing, using a combination of structured dialogue and quantitative analysis. Focus group discussions with Maasai pastoralists in three different pastoral regions, performed by in‐country experts, minimized the risk of cross‐cultural misinterpretation through a platform of shared Kenyan heritage.
In our survey of 213 Maasai pastoralist communities, we found universal agreement that humans and lions should coexist in Kenya.
Maasai communities distinguished among drought, disease, theft, loss and depredation as drivers of livestock losses. Maasai also distinguished among predatory species that take their livestock. The only cause of livestock loss that provoked increased killing of lions, was depredation by lions. Lion‐killing was not provoked by other predatory species. We found regional variation in the baseline probability of lion‐killing, and discuss the sources of this variation.
The probability of lion‐killing increases as an act of retribution for predation of livestock that discriminates among species of carnivore. This, coupled with universal acceptance of coexistence between lions and Maasai pastoralists, should guide mitigation strategies for human–wildlife interactions in Kenya and beyond.
A plain language summary is available for this article.
Abstract.
Colchero F, Jones OR, Conde DA, Hodgson D, Zajitschek F, Schmidt BR, Malo AF, Alberts SC, Becker PH, Bouwhuis S, et al (2019). The diversity of population responses to environmental change.
Ecol Lett,
22(2), 342-353.
Abstract:
The diversity of population responses to environmental change.
The current extinction and climate change crises pressure us to predict population dynamics with ever-greater accuracy. Although predictions rest on the well-advanced theory of age-structured populations, two key issues remain poorly explored. Specifically, how the age-dependency in demographic rates and the year-to-year interactions between survival and fecundity affect stochastic population growth rates. We use inference, simulations and mathematical derivations to explore how environmental perturbations determine population growth rates for populations with different age-specific demographic rates and when ages are reduced to stages. We find that stage- vs. age-based models can produce markedly divergent stochastic population growth rates. The differences are most pronounced when there are survival-fecundity-trade-offs, which reduce the variance in the population growth rate. Finally, the expected value and variance of the stochastic growth rates of populations with different age-specific demographic rates can diverge to the extent that, while some populations may thrive, others will inevitably go extinct.
Abstract.
Author URL.
2018
Harrison XA, Donaldson L, Correa-Cano ME, Evans J, Fisher DN, Goodwin CED, Robinson BS, Hodgson DJ, Inger R (2018). A brief introduction to mixed effects modelling and multi-model inference in ecology.
PeerJ,
6Abstract:
A brief introduction to mixed effects modelling and multi-model inference in ecology.
The use of linear mixed effects models (LMMs) is increasingly common in the analysis of biological data. Whilst LMMs offer a flexible approach to modelling a broad range of data types, ecological data are often complex and require complex model structures, and the fitting and interpretation of such models is not always straightforward. The ability to achieve robust biological inference requires that practitioners know how and when to apply these tools. Here, we provide a general overview of current methods for the application of LMMs to biological data, and highlight the typical pitfalls that can be encountered in the statistical modelling process. We tackle several issues regarding methods of model selection, with particular reference to the use of information theory and multi-model inference in ecology. We offer practical solutions and direct the reader to key references that provide further technical detail for those seeking a deeper understanding. This overview should serve as a widely accessible code of best practice for applying LMMs to complex biological problems and model structures, and in doing so improve the robustness of conclusions drawn from studies investigating ecological and evolutionary questions.
Abstract.
Author URL.
Goodwin CED, Suggitt AJ, Bennie J, Silk MJ, Duffy JP, Al‐Fulaij N, Bailey S, Hodgson DJ, McDonald RA (2018). Climate, landscape, habitat, and woodland management associations with hazel dormouse <i>Muscardinus avellanarius</i> population status.
Mammal Review,
48(3), 209-223.
Abstract:
Climate, landscape, habitat, and woodland management associations with hazel dormouse Muscardinus avellanarius population status
Abstract
Although strictly protected, populations of the hazel dormouse Muscardinus avellanarius in the UK declined by 72% from 1993 to 2014. Using National Dormouse Monitoring Programme data from 300 sites throughout England and Wales, we investigated variation in hazel dormouse population status (expressed as Indices of Abundance, Breeding, and population Trend) in relation to climate, landscape, habitat, and woodland management.
Dormice were more abundant and produced more litters on sites with warmer, sunnier springs, summers, and autumns. Dormouse abundance was also higher on sites with consistently cold local climate in winter. Habitat connectivity, woodland species composition, and active site management were all correlated with greater dormouse abundance and breeding. Abundances were also higher on sites with successional habitats, whereas the abundance of early successional bramble Rubus fruticosus habitat, woodland area, and landscape connectivity were important for population stability.
Diversity in the structure of woodlands in Europe has decreased over the last 100 years, and the habitats we found to be associated with more favourable dormouse status have also been in decline. The conservation status of the hazel dormouse, and that of woodland birds and butterflies, may benefit from reinstatement or increased frequency of management practices, such as coppicing and glade management, that maintain successional and diverse habitats within woodland.
Abstract.
Clay TA, Mangel JC, Alfaro-Shigueto J, Hodgson DJ, Godley BJ (2018). Distribution and habitat use of a cryptic small cetacean, the Burmeister's porpoise, monitored from a small-scale fishery platform.
Frontiers in Marine Science,
5(JUL).
Abstract:
Distribution and habitat use of a cryptic small cetacean, the Burmeister's porpoise, monitored from a small-scale fishery platform
There is widespread evidence that small-scale fisheries (SSF) bycatch threatens many populations of small cetaceans, yet conservation efforts are often limited by a lack of basic knowledge regarding their abundance, distribution, and habitat use. Here, we used passive acoustic monitoring from an SSF platform-of-opportunity to better characterize the distribution and habitat use of small cetaceans in northern Peru, focussing on the little-known Burmeister's porpoise Phocoena spinipinnis. From 2009 to 2012, acoustic click detectors (C-PODs) were attached to fishing nets for the duration of 116 fishing sets (30 fishing trips). Dolphins (unspecified delphinids) and porpoises were recorded around 71 and 22% of fishing sets, respectively. The probability of occurrence and buzzing behavior (a proxy for foraging), and time spent, were linked to both static and dynamic environmental variables to examine the drivers of habitat use. Dolphin activity was spread evenly throughout the fishing area and was not linked to any habitat variables. In contrast, porpoises were detected in neritic waters, and habitat models performed well, identifying preferences for shallow (< 200 m depth) and cooler (17-18°C) waters, close (< 50 km) to shore. The high bycatch rate of small cetaceans in Peruvian SSF gave us the unique opportunity to investigate the link between bycatch and cetacean activity around vessels. We found a positive relationship between the likelihood of a bycatch event and acoustic presence for both dolphins and porpoises, however as we did not know the timing of entanglement, we could not link vocalization rates to mortality events. Nonetheless, as small cetaceans (particularly dolphins) frequently encounter fishing boats, the likelihood of entanglements may be reduced through effective efforts to alert animals to the presence of the net, either acoustically (using acoustic alarms) or visually. This study demonstrates that passive acoustic monitoring from a fisheries platform can provide insights into the distribution and habitat use of small cetaceans at relatively low cost, and is likely to be suitable in regions with low monitoring effort and high fishing pressure.
Abstract.
Hesse E, O'Brien S, Tromas N, Bayer F, Luján AM, van Veen EM, Hodgson DJ, Buckling A (2018). Ecological selection of siderophore-producing microbial taxa in response to heavy metal contamination.
Ecol Lett,
21(1), 117-127.
Abstract:
Ecological selection of siderophore-producing microbial taxa in response to heavy metal contamination.
Some microbial public goods can provide both individual and community-wide benefits, and are open to exploitation by non-producing species. One such example is the production of metal-detoxifying siderophores. Here, we investigate whether conflicting selection pressures on siderophore production by heavy metals - a detoxifying effect of siderophores, and exploitation of this detoxifying effect - result in a net increase or decrease. We show that the proportion of siderophore-producing taxa increases along a natural heavy metal gradient. A causal link between metal contamination and siderophore production was subsequently demonstrated in a microcosm experiment in compost, in which we observed changes in community composition towards taxa that produce relatively more siderophores following copper contamination. We confirmed the selective benefit of siderophores by showing that taxa producing large amounts of siderophore suffered less growth inhibition in toxic copper. Our results suggest that ecological selection will favour siderophore-mediated decontamination, with important consequences for potential remediation strategies.
Abstract.
Author URL.
Hesse E, Hodgson DJ, de Jong TJ (2018). Glucosinolates promote initial population establishment of feral oilseed rape.
Goodwin CED, Hodgson DJ, Bailey S, Bennie J, McDonald RA (2018). Habitat preferences of hazel dormice Muscardinus avellanarius and the effects of tree-felling on their movement.
Forest Ecology and Management,
427, 190-199.
Abstract:
Habitat preferences of hazel dormice Muscardinus avellanarius and the effects of tree-felling on their movement
Modern management of multifunctional woodlands must address many and various demands, including for recreation, timber production and the conservation of biodiversity. The responses of individuals and populations of protected species to woodland management and habitat change are often not well understood. Using radio-tracking and LiDAR, we investigated the short-term habitat preferences of hazel dormice Muscardinus avellanarius, and their ranging and resting behaviours before and after small-scale tree felling, following a before-after control-impact design. Mean dormouse home range size was 0.51 Ha (±0.07 SE, n = 16) and did not vary between sexes or among sites, though heavier animals had smaller ranges. Dormice preferred mid-height woodland habitat (5–10 m tall), with low proportions of high forest (over 10 m tall), for both ranging and resting sites. Ranging habitats were often located on woodland edges and relatively dense vegetation. Dormice preferentially used yew, rowan and hazel during ranging. There was no difference in the distances travelled by dormice before and after felling, but dormice in areas where trees had been felled showed less evidence of a shift in ranging area than those in unfelled areas. Although the limited response of dormice to tree felling activities has the potential to be associated with increased mortality and/or limited dispersal of individual dormice, the requirements of dormice for mid-successional and edge habitats that arise after tree removal means that a dynamic optimum of felling and regeneration is essential for conservation of dormouse populations.
Abstract.
Benton CH, Delahay RJ, Smith FAP, Robertson A, McDonald RA, Young AJ, Burke TA, Hodgson D (2018). Inbreeding intensifies sex- and age-dependent disease in a wild mammal.
J Anim Ecol,
87(6), 1500-1511.
Abstract:
Inbreeding intensifies sex- and age-dependent disease in a wild mammal.
The mutation accumulation theory of senescence predicts that age-related deterioration of fitness can be exaggerated when inbreeding causes homozygosity for deleterious alleles. A vital component of fitness, in natural populations, is the incidence and progression of disease. Evidence is growing for natural links between inbreeding and ageing; between inbreeding and disease; between sex and ageing; and between sex and disease. However, there is scant evidence, to date, for links among age, disease, inbreeding and sex in a single natural population. Using ecological and epidemiological data from a long-term longitudinal field study, we show that in wild European badgers (Meles meles) exposed naturally to bovine tuberculosis (bTB), inbreeding (measured as multilocus homozygosity) intensifies a positive correlation between age and evidence of progressed infection (measured as an antibody response to bTB), but only among females. Male badgers suffer a steeper relationship between age and progressed infection than females, with no influence of inbred status. We found no link between inbreeding and the incidence of progressed infection during early life in either sex. Our findings highlight an age-related increase in the impact of inbreeding on a fitness-relevant trait (disease state) among females. This relationship is consistent with the predictions of the mutation accumulation theory of senescence, but other mechanisms could also play a role. For example, late-life declines in condition, arising through mechanisms other than mutation accumulation might have increased the magnitude of inbreeding depression in late life. Whichever mechanism causes the observed patterns, we have shown that inbreeding can influence age-dependent patterns of disease and, by extension, is likely to affect the magnitude and timing of the late-life declines in components of fitness that characterise senescence. Better understanding of sex-specific links between inbreeding, disease and ageing provides insights into population-level pathogen dynamics and could influence management strategies for wildlife reservoirs of zoonotic disease.
Abstract.
Author URL.
Nicol‑Harper A, Dooley C, Packman D, Mueller M, Bijak J, Hodgson D, Townley S, Ezard T (2018). Inferring transient dynamics of human populations from matrix non-normality. Population Ecology
O'Brien S, Hesse E, Luján A, Hodgson DJ, Gardner A, Buckling A (2018). No effect of intraspecific relatedness on public goods cooperation in a complex community.
Evolution,
72(5), 1165-1173.
Abstract:
No effect of intraspecific relatedness on public goods cooperation in a complex community.
Many organisms-notably microbes-are embedded within complex communities where cooperative behaviors in the form of excreted public goods can benefit other species. Under such circumstances, intraspecific interactions are likely to be less important in driving the evolution of cooperation. We first illustrate this idea with a simple theoretical model, showing that relatedness-the extent to which individuals with the same cooperative alleles interact with each other-has a reduced impact on the evolution of cooperation when public goods are shared between species. We test this empirically using strain of Pseudomonas aeruginosa that vary in their production of metal-chelating siderophores in copper contaminated compost (an interspecific public good). We show that nonsiderophore producers grow poorly relative to producers under high relatedness, but this cost can be alleviated by the presence of the isogenic producer (low relatedness) and/or the compost microbial community. Hence, relatedness can become unimportant when public goods provide interspecific benefits.
Abstract.
Author URL.
Pincheira-Donoso D, Hodgson DJ (2018). No evidence that extinction risk increases in the largest and smallest vertebrates.
Proc Natl Acad Sci U S A,
115(26), E5845-E5846.
Author URL.
McDonald JL, Hodgson DJ (2018). Prior precision, prior accuracy, and the estimation of disease prevalence using imperfect diagnostic tests.
Frontiers in Veterinary Science,
5(MAY).
Abstract:
Prior precision, prior accuracy, and the estimation of disease prevalence using imperfect diagnostic tests
Estimates of disease prevalence in any host population are complicated by uncertainty in the outcome of diagnostic tests on individuals. In the absence of gold standard diagnostics (tests that give neither false positives nor false negatives), Bayesian latent class inference can be applied to batteries of diagnostic tests, providing posterior estimates of the sensitivity and specificity of each test, alongside posterior estimates of disease prevalence. Here we explore the influence of precision and accuracy of prior information on the precision and accuracy of posterior estimates of these key parameters. Our simulations use three diagnostic tests, yielding eight possible diagnostic outcomes per individual. Seven degrees of freedom allow the estimation of seven parameters: sensitivity and specificity of each test, and disease prevalence. We show that prior precision begets posterior precision but only when priors are accurate. We also show that analyses without gold standard can use imprecise priors as long as they are initialised with accuracy. Imprecise priors risk the divergence of MCMC chains towards inaccurate posterior estimates, if inaccurate initial values are used. We note that inaccurate priors can yield inaccurate and imprecise inference. Bounded priors should certainly not be used unless their accuracy is well established. Inaccurate estimates of sensitivity or specificity can yield wildly inaccurate estimates of disease prevalence. Our analyses are motivated by studies of bovine tuberculosis in a wild badger population.
Abstract.
Pincheira-Donoso D, Tregenza T, Butlin R, Hodgson DJ (2018). Sexes and species as rival units of niche saturation during community assembly. Global Ecology and Biogeography
Rozins C, Silk MJ, Croft DP, Delahay RJ, Hodgson DJ, McDonald RA, Weber N, Boots M (2018). Social structure contains epidemics and regulates individual roles in disease transmission in a group-living mammal.
Ecology and Evolution,
8(23), 12044-12055.
Abstract:
Social structure contains epidemics and regulates individual roles in disease transmission in a group-living mammal
Population structure is critical to infectious disease transmission. As a result, theoretical and empirical contact network models of infectious disease spread are increasingly providing valuable insights into wildlife epidemiology. Analyzing an exceptionally detailed dataset on contact structure within a high-density population of European badgers Meles meles, we show that a modular contact network produced by spatially structured stable social groups, lead to smaller epidemics, particularly for infections with intermediate transmissibility. The key advance is that we identify considerable variation among individuals in their role in disease spread, with these new insights made possible by the detail in the badger dataset. Furthermore, the important impacts on epidemiology are found even though the modularity of the Badger network is much lower than the threshold that previous work suggested was necessary. These findings reveal the importance of stable social group structure for disease dynamics with important management implications for socially structured populations.
Abstract.
Jelbert K (2018). The Comparative Demography of Invasive Plants.
Abstract:
The Comparative Demography of Invasive Plants
Biodiversity, ecosystems, industry and human health are threatened by invasive plant species. The costs of mitigating damages run into billions of pounds per annum. Fundamental to the control of invasive plant species is an ability to predict which species will become invasive. Yet identification of predictive differences between invasive and non-invasive species has proven difficult to pinpoint. In this thesis I identify several weaknesses within published literature, and using field experiments and meta-analyses we address these to find consistent predictors of invasiveness amongst plants. Specifically, I recognize that predictors of invasiveness can be identified by studying plant species in the native range because species may undergo phenotypic and demographic changes following naturalization (Chapters 2 – 5). I also recognize the importance of comparing globally invasive and non-invasive species, and the importance of accounting for phylogenetic relationships so as not to inflate or conceal differences (Chapters 2 – 4). Finally, I investigate whether particular analyses are more appropriate for investigating life history and demographic differences (Chapter 5).
This thesis comprises an introductory chapter (Chapter 1), four data chapters (Chapters 2 - 5) and a general discussion (Chapter 6). Chapters 2 and 3 compare life history traits of plant species known to be invasive elsewhere, with their exported but non-invasive sympatric relatives in the native range. Chapter 4 utilizes Population Projection Matrices held within the COMPADRE Plant Matrix Database, to compare demographic projections of stable and transient dynamics of invasive and non-invasive plants; and Chapter 5 compares ten metrics, derived from Population Projection Matrices, of seven invasive species between the native and invaded range to determine if there are demographic or life history differences that facilitate invasion, and to identify those analyses that are most likely to reveal such differences.
I find reproductive capacity to be a predictor of invasiveness, and that analyses of transient dynamics are more likely than analyses of projected stable dynamics to reveal demographic or life history differences between invasive and non-invasive species or populations of plants. I discuss these findings in the context of invasive risk assessment protocols and highlight future research opportunities.
Abstract.
2017
Weegman MD, Fox AD, Hilton GM, Hodgson DJ, Walsh AJ, Griffin LR, Bearhop S (2017). Diagnosing the decline of the Greenland White-fronted Goose Anser albifrons flavirostris using population and individual level techniques.
Wildfowl,
67, 3-18.
Abstract:
Diagnosing the decline of the Greenland White-fronted Goose Anser albifrons flavirostris using population and individual level techniques
Following an increase in numbers from 1982 to 1998, the Greenland White-fronted Goose Anser albifrons flavirostris declined over the period 1999–2015, stimulating detailed analyses at the population and individual level to provide a better understanding of the dynamics of this subspecies. Here we synthesise the results of the analyses in order to describe the potential reasons for the decline. Utilising a 27-year capture-mark-recapture dataset from the main wintering site for these birds (Wexford, Ireland), multistate models estimated sex-specific survival and movement probabilities. Our results suggested no evidence of a sex bias in emigration or “remigration” rates. These analyses formed the foundation for an integrated population model (IPM), which included population size and productivity data to assess source-sink dynamics of Wexford birds through estimation of age-, site-, and year-specific survival and movement probabilities. Results from the IPM suggested that Wexford is a large sink, and that a reduction in productivity is an important demographic mechanism underlying population change for birds wintering at the site. Low productivity may be due to environmental conditions in the breeding range, because birds bred successfully at youngest ages when conditions in Greenland were favourable in the year(s) during adulthood prior to and including the year of successful breeding. This effect could be mediated by prolonged parent-offspring relationships, as birds remained with parents into adulthood, forfeiting immediate reproductive success despite there being no fitness benefits to offspring of family associations after age 3 years. Global Positioning System and acceleration data collected from 15 male individuals suggested that two successful breeding birds were the only tagged individuals whose mate exhibited prolonged incubation. More data is required, however, to determine whether poor productivity is attributable to deferral of nesting or to failure of nesting attempts. Spring foraging did not appear to limit breeding or migration distance because breeding and non-breeding or failed-breeding birds, as well as Irish and Scottish birds, did not differ in their proportion of time spent feeding or on energy expenditure in spring. We recommend that future research should quantify the demography of other Greenland White-fronted Goose wintering flocks, to assess holistically the mechanisms underlying the global population decline.
Abstract.
McDonald JL, Franco M, Townley S, Ezard THG, Jelbert K, Hodgson DJ (2017). Divergent demographic strategies of plants in variable environments. Nature Ecology & Evolution, 1(2).
Pincheira-Donoso D, Jara M, Reaney A, García-Roa R, Saldarriaga-Córdoba M, Hodgson DJ (2017). Hypoxia and hypothermia as rival agents of selection driving the evolution of viviparity in lizards.
Global Ecology and Biogeography,
26(11), 1238-1246.
Abstract:
Hypoxia and hypothermia as rival agents of selection driving the evolution of viviparity in lizards
Aim: the evolution of key innovations promotes adaptive radiations by opening access to new ecological opportunity. The acquisition of viviparity (live-bearing reproduction) has emerged as one such innovation explaining reptile proliferations into extreme climates. By evolving viviparity, females provide embryos with internally stable environments to complete development. The classical hypothesis suggests that natural selection for viviparity arises from low temperatures in cold climates, which promote prolonged egg retention in the mother's body. An alternative hypothesis proposes that declines in atmospheric oxygen at high elevations create natural selection for embryo retention to provide them with optimal oxygen levels during development. However, although experimental studies support the negative effects of low oxygen on egg development, this ‘hypoxia’ hypothesis has never been tested quantitatively. Here, we compete the hypoxia hypothesis against the ‘cold-climate’ hypothesis, using a highly diverse lizard genus. Location: South America. Major taxa: Liolaemus lizards. Methods: We use a multivariate dataset covering 121 species varying extensively in geographical and climatic distribution (including extreme thermal and oxygen gradients) and parity mode. Based on a new molecular phylogeny for the genus, we use phylogenetic logistic regressions to generate a range of models ranking environmental factors as a function of their effects on parity mode transitions. Results: Elevation and oxygen declines were almost perfectly correlated, and both were identified as the dominant predictors of oviparity-to-viviparity transitions, whereas the role for temperature (dominated by the coldest winter temperatures and daily fluctuations) was significant but secondary. Overall, we showed that oxygen deprivation and low temperatures both play a role in the evolution of viviparity. Main conclusions: Our findings support the role for selection from declines in oxygen concentrations as the primary driver behind viviparity. However, selection arising from cold temperatures and from reduced fluctuations in daily temperatures contributes to the evolution of these transitions by creating multivariate selection on parity mode.
Abstract.
Hodgson DJ, Bréchon AL, Thompson RC (2017). Ingestion and fragmentation of plastic carrier bags by the amphipod Orchestia gammarellus: Effects of plastic type and fouling load. Marine Pollution Bulletin, 127, 154-159.
Ellis CD, Hodgson DJ, Daniels CL, Collins M, Griffiths AGF (2017). Population genetic structure in European lobsters: Implications for connectivity, diversity and hatchery stocking.
Marine Ecology Progress Series,
563, 123-137.
Abstract:
Population genetic structure in European lobsters: Implications for connectivity, diversity and hatchery stocking
The European lobster Homarus gammarus is a marine crustacean prized for seafood, but populations across its range are threatened by fishery overexploitation. The species' larval stages are planktonic, suggesting considerable dispersal among populations. The potential threats of overexploitation and erosion of population structure due to hatchery releases or inadvertent introductions make it important to understand the genetic structuring of populations across multiple geographic scales. Here we assess lobster population structure at a fine scale in Cornwall, southwestern UK, where a hatchery-stocking operation introduces cultured individuals into the wild stock, and at a broader European level, in order to compare the spatial scale of hatchery releases with that of population connectivity. Microsatellite genotypes of 24 individuals from each of 13 locations in Cornwall showed no fine-scale population structure across distances of up to ~230 km. Significant differentiation and isolation by distance were detected at a broader scale, using 300 additional individuals comprising a further 15 European samples. Signals of genetic heterogeneity were evident between an Atlantic cluster and samples from Sweden. Connectivity within the Atlantic and Swedish clusters was high, although evidence for isolation by distance and a transitional zone within the eastern North Sea suggested that direct gene exchange between these stocks is limited and fits a stepping-stone model. We conclude that hatchery-reared lobsters should not be released where broodstock are distantly sourced but, using Cornwall as a case study, microsatellites revealed no evidence that the normal release of hatchery stock exceeds the geographic scale of natural connectivity.
Abstract.
Silk MJ, Croft DP, Delahay RJ, Hodgson DJ, Weber N, Boots M, Mcdonald RA (2017). The application of statistical network models in disease research.
Methods in Ecology and EvolutionAbstract:
The application of statistical network models in disease research
© 2017 British Ecological Society.Host social structure is fundamental to how infections spread and persist, and so the statistical modelling of static and dynamic social networks provides an invaluable tool to parameterise realistic epidemiological models. We present a practical guide to the application of network modelling frameworks for hypothesis testing related to social interactions and epidemiology, illustrating some approaches with worked examples using data from a population of wild European badgers Meles meles naturally infected with bovine tuberculosis. Different empirical network datasets generate particular statistical issues related to non-independence and sampling constraints. We therefore discuss the strengths and weaknesses of modelling approaches for different types of network data and for answering different questions relating to disease transmission. We argue that statistical modelling frameworks designed specifically for network analysis offer great potential in directly relating network structure to infection. They have the potential to be powerful tools in analysing empirical contact data used in epidemiological studies, but remain untested for use in networks of spatio-temporal associations. As a result, we argue that developments in the statistical analysis of empirical contact data are critical given the ready availability of dynamic network data from bio-logging studies. Furthermore, we encourage improved integration of statistical network approaches into epidemiological research to facilitate the generation of novel modelling frameworks and help extend our understanding of disease transmission in natural populations.
Abstract.
Goodwin CED, Hodgson DJ, Al-Fulaij N, Bailey S, Langton S, Mcdonald RA (2017). Voluntary recording scheme reveals ongoing decline in the United Kingdom hazel dormouse <i>Muscardinus avellanarius</i> population.
MAMMAL REVIEW,
47(3), 183-197.
Author URL.
2016
Guiver C, Hodgson D, Townley S (2016). A note on the eigenvectors of perturbed matrices with applications to linear positive systems.
Linear Algebra and its Applications,
509, 143-167.
Abstract:
A note on the eigenvectors of perturbed matrices with applications to linear positive systems
A result is presented describing the eigenvectors of a perturbed matrix, for a class of structured perturbations. One motivation for doing so is that positive eigenvectors of nonnegative, irreducible matrices are known to induce norms — acting much like Lyapunov functions — for linear positive systems, which may help estimate or control transient dynamics. The results apply to both discrete- and continuous-time linear positive systems. The theory is illustrated with several examples.
Abstract.
Benton CH, Delahay RJ, Robertson A, McDonald RA, Wilson AJ, Burke TA, Hodgson D (2016). Blood thicker than water: kinship, disease prevalence and group size drive divergent patterns of infection risk in a social mammal.
Proc Biol Sci,
283(1835).
Abstract:
Blood thicker than water: kinship, disease prevalence and group size drive divergent patterns of infection risk in a social mammal.
The importance of social- and kin-structuring of populations for the transmission of wildlife disease is widely assumed but poorly described. Social structure can help dilute risks of transmission for group members, and is relatively easy to measure, but kin-association represents a further level of population sub-structure that is harder to measure, particularly when association behaviours happen underground. Here, using epidemiological and molecular genetic data from a wild, high-density population of the European badger (Meles meles), we quantify the risks of infection with Mycobacterium bovis (the causative agent of tuberculosis) in cubs. The risk declines with increasing size of its social group, but this net dilution effect conceals divergent patterns of infection risk. Cubs only enjoy reduced risk when social groups have a higher proportion of test-negative individuals. Cubs suffer higher infection risk in social groups containing resident infectious adults, and these risks are exaggerated when cubs and infectious adults are closely related. We further identify key differences in infection risk associated with resident infectious males and females. We link our results to parent-offspring interactions and other kin-biased association, but also consider the possibility that susceptibility to infection is heritable. These patterns of infection risk help to explain the observation of a herd immunity effect in badgers following low-intensity vaccination campaigns. They also reveal kinship and kin-association to be important, and often hidden, drivers of disease transmission in social mammals.
Abstract.
Author URL.
Salguero-Gómez R, Jones OR, Archer CR, Bein C, de Buhr H, Farack C, Gottschalk F, Hartmann A, Henning A, Hoppe G, et al (2016). COMADRE: a global data base of animal demography.
J Anim Ecol,
85(2), 371-384.
Abstract:
COMADRE: a global data base of animal demography.
UNLABELLED: the open-data scientific philosophy is being widely adopted and proving to promote considerable progress in ecology and evolution. Open-data global data bases now exist on animal migration, species distribution, conservation status, etc. However, a gap exists for data on population dynamics spanning the rich diversity of the animal kingdom world-wide. This information is fundamental to our understanding of the conditions that have shaped variation in animal life histories and their relationships with the environment, as well as the determinants of invasion and extinction. Matrix population models (MPMs) are among the most widely used demographic tools by animal ecologists. MPMs project population dynamics based on the reproduction, survival and development of individuals in a population over their life cycle. The outputs from MPMs have direct biological interpretations, facilitating comparisons among animal species as different as Caenorhabditis elegans, Loxodonta africana and Homo sapiens. Thousands of animal demographic records exist in the form of MPMs, but they are dispersed throughout the literature, rendering comparative analyses difficult. Here, we introduce the COMADRE Animal Matrix Database, an open-data online repository, which in its version 1.0.0 contains data on 345 species world-wide, from 402 studies with a total of 1625 population projection matrices. COMADRE also contains ancillary information (e.g. ecoregion, taxonomy, biogeography, etc.) that facilitates interpretation of the numerous demographic metrics that can be derived from its MPMs. We provide R code to some of these examples. SYNTHESIS: We introduce the COMADRE Animal Matrix Database, a resource for animal demography. Its open-data nature, together with its ancillary information, will facilitate comparative analysis, as will the growing availability of databases focusing on other aspects of the rich animal diversity, and tools to query and combine them. Through future frequent updates of COMADRE, and its integration with other online resources, we encourage animal ecologists to tackle global ecological and evolutionary questions with unprecedented sample size.
Abstract.
Author URL.
McDonald JL, Bailey T, Delahay RJ, McDonald RA, Smith GC, Hodgson DJ (2016). Demographic buffering and compensatory recruitment promotes the persistence of disease in a wildlife population. Ecology Letters (under final revision)
Salguero-Gómez R, Jones OR, Jongejans E, Blomberg SP, Hodgson DJ, Mbeau-Ache C, Zuidema PA, de Kroon H, Buckley YM (2016). Fast-slow continuum and reproductive strategies structure plant life-history variation worldwide.
Proc Natl Acad Sci U S A,
113(1), 230-235.
Abstract:
Fast-slow continuum and reproductive strategies structure plant life-history variation worldwide.
The identification of patterns in life-history strategies across the tree of life is essential to our prediction of population persistence, extinction, and diversification. Plants exhibit a wide range of patterns of longevity, growth, and reproduction, but the general determinants of this enormous variation in life history are poorly understood. We use demographic data from 418 plant species in the wild, from annual herbs to supercentennial trees, to examine how growth form, habitat, and phylogenetic relationships structure plant life histories and to develop a framework to predict population performance. We show that 55% of the variation in plant life-history strategies is adequately characterized using two independent axes: the fast-slow continuum, including fast-growing, short-lived plant species at one end and slow-growing, long-lived species at the other, and a reproductive strategy axis, with highly reproductive, iteroparous species at one extreme and poorly reproductive, semelparous plants with frequent shrinkage at the other. Our findings remain consistent across major habitats and are minimally affected by plant growth form and phylogenetic ancestry, suggesting that the relative independence of the fast-slow and reproduction strategy axes is general in the plant kingdom. Our findings have similarities with how life-history strategies are structured in mammals, birds, and reptiles. The position of plant species populations in the 2D space produced by both axes predicts their rate of recovery from disturbances and population growth rate. This life-history framework may complement trait-based frameworks on leaf and wood economics; together these frameworks may allow prediction of responses of plants to anthropogenic disturbances and changing environments.
Abstract.
Author URL.
Weegman MD, Bearhop S, Fox AD, Hilton GM, Walsh AJ, McDonald JL, Hodgson DJ (2016). Integrated population modelling reveals a perceived source to be a cryptic sink.
J Anim Ecol,
85(2), 467-475.
Abstract:
Integrated population modelling reveals a perceived source to be a cryptic sink.
Demographic links among fragmented populations are commonly studied as source-sink dynamics, whereby source populations exhibit net recruitment and net emigration, while sinks suffer net mortality but enjoy net immigration. It is commonly assumed that large, persistent aggregations of individuals must be sources, but this ignores the possibility that they are sinks instead, buoyed demographically by immigration. We tested this assumption using Bayesian integrated population modelling of Greenland white-fronted geese (Anser albifrons flavirostris) at their largest wintering site (Wexford, Ireland), combining capture-mark-recapture, census and recruitment data collected from 1982 to 2010. Management for this subspecies occurs largely on wintering areas; thus, study of source-sink dynamics of discrete regular wintering units provides unprecedented insights into population regulation and enables identification of likely processes influencing population dynamics at Wexford and among 70 other Greenland white-fronted goose wintering subpopulations. Using results from integrated population modelling, we parameterized an age-structured population projection matrix to determine the contribution of movement rates (emigration and immigration), recruitment and mortality to the dynamics of the Wexford subpopulation. Survival estimates for juvenile and adult birds at Wexford and adult birds elsewhere fluctuated over the 29-year study period, but were not identifiably different. However, per capita recruitment rates at Wexford in later years (post-1995) were identifiably lower than in earlier years (pre-1995). The observed persistence of the Wexford subpopulation was only possible with high rates of immigration, which exceeded emigration in each year. Thus, despite its apparent stability, Wexford has functioned as a sink over the entire study period. These results demonstrate that even large subpopulations can potentially be sinks, and that movement dynamics (e.g. immigration) among winters can dramatically obscure key processes driving subpopulation size. Further, novel population models which integrate capture-mark-recapture, census and recruitment data are essential to correctly ascribing source-sink status and accurately informing development of site-safeguard networks.
Abstract.
Author URL.
Ffrench-Constant RH, Somers-Yeates R, Bennie J, Economou T, Hodgson D, Spalding A, McGregor PK (2016). Light pollution is associated with earlier tree budburst across the United Kingdom. Proceedings of the Royal Society of London. Series B
Guiver C, Mueller M, Hodgson D, Townley S (2016). Robust set-point regulation for ecological models with multiple management goals.
J Math Biol,
72(6), 1467-1529.
Abstract:
Robust set-point regulation for ecological models with multiple management goals.
Population managers will often have to deal with problems of meeting multiple goals, for example, keeping at specific levels both the total population and population abundances in given stage-classes of a stratified population. In control engineering, such set-point regulation problems are commonly tackled using multi-input, multi-output proportional and integral (PI) feedback controllers. Building on our recent results for population management with single goals, we develop a PI control approach in a context of multi-objective population management. We show that robust set-point regulation is achieved by using a modified PI controller with saturation and anti-windup elements, both described in the paper, and illustrate the theory with examples. Our results apply more generally to linear control systems with positive state variables, including a class of infinite-dimensional systems, and thus have broader appeal.
Abstract.
Author URL.
Weegman MD, Bearhop S, Hilton GM, Walsh AJ, Weegman KM, Hodgson DJ, Fox AD (2016). Should I stay or should I go? Fitness costs and benefits of prolonged parent-offspring and sibling-sibling associations in an Arctic-nesting goose population.
Oecologia,
181(3), 809-817.
Abstract:
Should I stay or should I go? Fitness costs and benefits of prolonged parent-offspring and sibling-sibling associations in an Arctic-nesting goose population.
Theory predicts persistence of long-term family relationships in vertebrates will occur until perceived fitness costs exceed benefits to either parents or offspring. We examined whether increased breeding probability and survival were associated with prolonged parent-offspring and sibling-sibling relationships in a long-lived Arctic migrant herbivore, the Greenland white-fronted goose (Anser albifrons flavirostris). Although offspring associated with parents for 1-13 years, 79 % of these associations lasted two or less years. Only 65 (9.9 %) of the 656 marked offspring bred once in their lifetime, and just 16 (2.4 %) bred twice or more. The probability of birds with siblings breeding successfully in a subsequent year was credibly greater than that of independent birds at ages 5, 6, and 7. Survival of offspring with parents was credibly greater than that of independent/nonbreeder birds at all possible ages (i.e. ages 2-7+). A cost-benefit matrix model utilizing breeding and survival probabilities showed that staying with family groups was favored over leaving until age 3, after which there were no credible differences between staying and leaving strategies until the oldest ages, when leaving family groups was favored. Thus, most birds in this study either departed family groups early (e.g. at age 2, when the "stay" strategy was favored) or as predicted by our cost-benefit model (i.e. at age 3). Although extended family associations are a feature of this population, we contend that the survival benefits are not sufficient enough to yield clear fitness benefits, and associations only persist because parents and offspring mutually benefit from their persistence.
Abstract.
Author URL.
Mills CA, Godley BJ, Hodgson DJ (2016). Take Only Photographs, Leave Only Footprints: Novel Applications of Non-Invasive Survey Methods for Rapid Detection of Small, Arboreal Animals.
PLoS One,
11(1).
Abstract:
Take Only Photographs, Leave Only Footprints: Novel Applications of Non-Invasive Survey Methods for Rapid Detection of Small, Arboreal Animals.
The development of appropriate wildlife survey techniques is essential to promote effective and efficient monitoring of species of conservation concern. Here, we demonstrate the utility of two rapid-assessment, non-invasive methods to detect the presence of elusive, small, arboreal animals. We use the hazel dormouse, Muscardinus avellanarius, a rodent of conservation concern, as our focal species. Prevailing hazel dormouse survey methods are prolonged (often taking months to years to detect dormice), dependent on season and habitat, and/or have low detection rates. Alternatives would be of great use to ecologists who undertake dormouse surveys, especially those assessing the need for mitigation measures, as legally required for building development projects. Camera traps and footprint tracking are well-established tools for monitoring elusive large terrestrial mammals, but are rarely used for small species such as rodents, or in arboreal habitats. In trials of these adapted methods, hazel dormice visited bait stations and were successfully detected by both camera traps and tracking equipment at each of two woodland study sites, within days to weeks of installation. Camera trap images and footprints were of adequate quality to allow discrimination between two sympatric small mammal species (hazel dormouse and wood mouse, Apodemus sylvaticus). We discuss the relative merits of these methods with respect to research aims, funds, time available and habitat.
Abstract.
Author URL.
Ozden O, Hodgson DJ (2016). The impact of tillage and chemical management on beneficial arthropods in Mediterranean olive groves.
Israel Journal of Ecology and Evolution,
63(1), 14-18.
Abstract:
The impact of tillage and chemical management on beneficial arthropods in Mediterranean olive groves
Woodlice (Isopoda: Oniscidae) are known to play important roles in soil profile development and nutrient cycling in agroecosystems. The aim of the present work was to understand the impact of different management regimes on woodlouse fauna in Mediterranean olive groves. The olive groves were located along the Kyrenia mountain range towards the north-west of Cyprus at two different elevations. We used pitfall trapping to compare the abundance of woodlice in groves that were (a) uncultivated at low altitude; (b) uncultivated at high altitude; (c) tilled at low altitude; (d) tilled and chemically managed at low altitude. A total of 1751 woodlice were collected and a significant effect of management regime on the abundance of woodlouse was observed. The low altitude uncultivated olive groves retained a higher number of individuals than the other three management regimes. Our results suggest that tillage alone did not impact severely on woodlouse abundance, but that tillage combined with pesticide and fertilizer application could lead to significant losses in woodlouse abundance in olive grove agroecosystems, with implications for the sustainability of soil quality and biodiversity.
Abstract.
Mcdonald JL, Stott I, Townley S, Hodgson DJ (2016). Transients drive the demographic dynamics of plant populations in variable environments.
Journal of Ecology,
104(2), 306-314.
Abstract:
Transients drive the demographic dynamics of plant populations in variable environments
The dynamics of structured plant populations in variable environments can be decomposed into the 'asymptotic' growth contributed by vital rates, and 'transient' growth caused by deviation from stable stage structure. We apply this framework to a large, global data base of longitudinal studies of projection matrix models for plant populations. We ask, what is the relative contribution of transient boom and bust to the dynamic trajectories of plant populations in stochastic environments? is this contribution patterned by phylogeny, growth form or the number of life stages per population and per species? We show that transients contribute nearly 50% or more to the resulting trajectories, depending on whether transient and stable contributions are partitioned according to their absolute or net contribution to population dynamics. Both transient contributions and asymptotic contributions are influenced heavily by the number of life stages modelled. We discuss whether the drivers of transients should be considered real ecological phenomena, or artefacts of study design and modelling strategy. We find no evidence for phylogenetic signal in the contribution of transients to stochastic growth, nor clear patterns related to growth form. We find a surprising tendency for plant populations to boom rather than bust in response to temporal changes in vital rates and that stochastic growth rates increase with increasing tendency to boom. Synthesis. Transient dynamics contribute significantly to stochastic population dynamics but are often overlooked in ecological and evolutionary studies that employ stochastic analyses. Better understanding of transient responses to fluctuating population structure will yield better management strategies for plant populations, and better grasp of evolutionary dynamics in the real world. Transient dynamics contribute significantly to stochastic population dynamics but are often overlooked in ecological and evolutionary studies that employ stochastic analyses. Better understanding of transient responses to fluctuating population structure will yield better management strategies for plant populations, and better grasp of evolutionary dynamics in the real world.
Abstract.
McDonald JL, Stott I, Townley S, Hodgson DJ, Griffith A (2016). Transients drive the demographic dynamics of plant populations in variable environments.
Journal of Ecology.,
104(2), 306-314.
Abstract:
Transients drive the demographic dynamics of plant populations in variable environments
The dynamics of structured plant populations in variable environments can be decomposed into the ‘asymptotic’ growth contributed by vital rates, and ‘transient’ growth caused by deviation from stable stage structure. We apply this framework to a large, global data base of longitudinal studies of projection matrix models for plant populations. We ask, what is the relative contribution of transient boom and bust to the dynamic trajectories of plant populations in stochastic environments? is this contribution patterned by phylogeny, growth form or the number of life stages per population and per species? We show that transients contribute nearly 50% or more to the resulting trajectories, depending on whether transient and stable contributions are partitioned according to their absolute or net contribution to population dynamics. Both transient contributions and asymptotic contributions are influenced heavily by the number of life stages modelled. We discuss whether the drivers of transients should be considered real ecological phenomena, or artefacts of study design and modelling strategy. We find no evidence for phylogenetic signal in the contribution of transients to stochastic growth, nor clear patterns related to growth form. We find a surprising tendency for plant populations to boom rather than bust in response to temporal changes in vital rates and that stochastic growth rates increase with increasing tendency to boom. Synthesis. Transient dynamics contribute significantly to stochastic population dynamics but are often overlooked in ecological and evolutionary studies that employ stochastic analyses. Better understanding of transient responses to fluctuating population structure will yield better management strategies for plant populations, and better grasp of evolutionary dynamics in the real world.
Abstract.
2015
North AC, Hodgson DJ, Price SJ, Griffiths AGF (2015). Anthropogenic and ecological drivers of amphibian disease (ranavirosis).
PLoS One,
10(6).
Abstract:
Anthropogenic and ecological drivers of amphibian disease (ranavirosis).
Ranaviruses are causing mass amphibian die-offs in North America, Europe and Asia, and have been implicated in the decline of common frog (Rana temporaria) populations in the UK. Despite this, we have very little understanding of the environmental drivers of disease occurrence and prevalence. Using a long term (1992-2000) dataset of public reports of amphibian mortalities, we assess a set of potential predictors of the occurrence and prevalence of Ranavirus-consistent common frog mortality events in Britain. We reveal the influence of biotic and abiotic drivers of this disease, with many of these abiotic characteristics being anthropogenic. Whilst controlling for the geographic distribution of mortality events, disease prevalence increases with increasing frog population density, presence of fish and wild newts, increasing pond depth and the use of garden chemicals. The presence of an alternative host reduces prevalence, potentially indicating a dilution effect. Ranavirosis occurrence is associated with the presence of toads, an urban setting and the use of fish care products, providing insight into the causes of emergence of disease. Links between occurrence, prevalence, pond characteristics and garden management practices provides useful management implications for reducing the impacts of Ranavirus in the wild.
Abstract.
Author URL.
Goodey NA, Florance HV, Smirnoff N, Hodgson DJ (2015). Aphids Pick Their Poison: Selective Sequestration of Plant Chemicals Affects Host Plant Use in a Specialist Herbivore.
J Chem Ecol,
41(10), 956-964.
Abstract:
Aphids Pick Their Poison: Selective Sequestration of Plant Chemicals Affects Host Plant Use in a Specialist Herbivore.
In some plant-insect interactions, specialist herbivores exploit the chemical defenses of their food plant to their own advantage. Brassica plants produce glucosinolates that are broken down into defensive toxins when tissue is damaged, but the specialist aphid, Brevicoryne brassicae, uses these chemicals against its own natural enemies by becoming a "walking mustard-oil bomb". Analysis of glucosinolate concentrations in plant tissue and associated aphid colonies reveals that not only do aphids sequester glucosinolates, but they do so selectively. Aphids specifically accumulate sinigrin to high concentrations while preferentially excreting a structurally similar glucosinolate, progoitrin. Surveys of aphid infestation in wild populations of Brassica oleracea show that this pattern of sequestration and excretion maps onto host plant use. The probability of aphid infestation decreases with increasing concentrations of progoitrin in plants. Brassica brassicae, therefore, appear to select among food plants according to plant secondary metabolite profiles, and selectively store only some compounds that are used against their own enemies. The results demonstrate chemical and behavioral mechanisms that help to explain evidence of geographic patterns and evolutionary dynamics in Brassica-aphid interactions.
Abstract.
Author URL.
Goodhead RM, Johnston BD, Cole PA, Baalousha M, Hodgson D, Iguchi T, Lead JR, Tyler CR (2015). Does natural organic matter increase the bioavailability of cerium dioxide nanoparticles to fish?.
Abstract:
Does natural organic matter increase the bioavailability of cerium dioxide nanoparticles to fish?
Abstract.
Ellis CD, Hodgson DJ, Daniels CL, Boothroyd DP, Bannister RCA, Griffiths AGF (2015). European lobster stocking requires comprehensive impact assessment to determine fishery benefits.
Abstract:
European lobster stocking requires comprehensive impact assessment to determine fishery benefits
Abstract.
Ellis CD, Hodgson DJ, André C, Sørdalen TK, Knutsen H, Griffiths AGF (2015). Genotype Reconstruction of Paternity in European Lobsters (Homarus gammarus).
PLoS One,
10(11).
Abstract:
Genotype Reconstruction of Paternity in European Lobsters (Homarus gammarus).
Decapod crustaceans exhibit considerable variation in fertilisation strategies, ranging from pervasive single paternity to the near-ubiquitous presence of multiple paternity, and such knowledge of mating systems and behaviour are required for the informed management of commercially-exploited marine fisheries. We used genetic markers to assess the paternity of individual broods in the European lobster, Homarus gammarus, a species for which paternity structure is unknown. Using 13 multiplexed microsatellite loci, three of which are newly described in this study, we genotyped 10 eggs from each of 34 females collected from an Atlantic peninsula in the south-western United Kingdom. Single reconstructed paternal genotypes explained all observed progeny genotypes in each of the 34 egg clutches, and each clutch was fertilised by a different male. Simulations indicated that the probability of detecting multiple paternity was in excess of 95% if secondary sires account for at least a quarter of the brood, and in excess of 99% where additional sire success was approximately equal. Our results show that multiple paternal fertilisations are either absent, unusual, or highly skewed in favour of a single male among H. gammarus in this area. Potential mechanisms upholding single paternal fertilisation are discussed, along with the prospective utility of parentage assignments in evaluations of hatchery stocking and other fishery conservation approaches in light of this finding.
Abstract.
Author URL.
Ellis CD, Knott H, Daniels CL, Witt MJ, Hodgson DJ (2015). Geographic and environmental drivers of fecundity in the European lobster (Homarus gammarus).
ICES Journal of Marine Science,
72, i91-i100.
Abstract:
Geographic and environmental drivers of fecundity in the European lobster (Homarus gammarus)
Fecundity in the European lobster (Homarus gammarus) has been shown to exhibit extensive spatial variation across northern Europe. Previously, this has been attributed to a lack of methodological standardization among samples. Instead, we show significant correlations between fecundity and both geographical and environmental drivers. We use linear mixed-effect models to assess the contribution of latitude, longitude, and measures of sea surface temperatures on the size-fecundity relationships of 1058 ovigerous females from 11 locations in the UK, Ireland, and Norway. We include new data for 52 lobsters from Falmouth, UK, the southwest limit of existing samples. Fecundity at mean female size correlated positively with eastings and greater annual ranges in sea surface temperature, but not with mean temperature or latitude. This contradicts the established latitudinal and mean temperature dependence reported for the closely related H. americanus. We postulate that proximity to stable Atlantic currents is the most likely driver of the relationship between fecundity and longitude. Mechanisms are discussed by which egg production or retention may be influenced by temperature range rather than by mean temperature. With further validation, we propose that temperature-correlated fecundity predictions will provide a valuable tool in ensuring that management thresholds are appropriate for the reproductive characteristics of lobster populations.
Abstract.
Guiver C, Logemann H, Rebarber R, Bill A, Tenhumberg B, Hodgson D, Townley S (2015). Integral control for population management.
J Math Biol,
70(5), 1015-1063.
Abstract:
Integral control for population management.
We present a novel management methodology for restocking a declining population. The strategy uses integral control, a concept ubiquitous in control theory which has not been applied to population dynamics. Integral control is based on dynamic feedback-using measurements of the population to inform management strategies and is robust to model uncertainty, an important consideration for ecological models. We demonstrate from first principles why such an approach to population management is suitable via theory and examples.
Abstract.
Author URL.
Jelbert K, Stott I, Mcdonald RA, Hodgson D (2015). Invasiveness of plants is predicted by size and fecundity in the native range.
Ecology and EvolutionAbstract:
Invasiveness of plants is predicted by size and fecundity in the native range
An important goal for invasive species research is to find key traits of species that predispose them to being invasive outside their native range. Comparative studies have revealed phenotypic and demographic traits that correlate with invasiveness among plants. However, all but a few previous studies have been performed in the invaded range, an approach which potentially conflates predictors of invasiveness with changes that happen during the invasion process itself. Here, we focus on wild plants in their native range to compare life-history traits of species known to be invasive elsewhere, with their exported but noninvasive relatives. Specifically, we test four hypotheses: that invasive plant species (1) are larger; (2) are more fecund; (3) exhibit higher fecundity for a given size; and (4) attempt to make seed more frequently, than their noninvasive relatives in the native range. We control for the effects of environment and phylogeny using sympatric congeneric or confamilial pairs in the native range. We find that invasive species are larger than noninvasive relatives. Greater size yields greater fecundity, but we also find that invasives are more fecund per-unit-size. Synthesis: We provide the first multispecies, taxonomically controlled comparison of size, and fecundity of invasive versus noninvasive plants in their native range. We find that invasive species are bigger, and produce more seeds, even when we account for their differences in size. Our findings demonstrate that invasive plant species are likely to be invasive as a result of both greater size and constitutively higher fecundity. This suggests that size and fecundity, relative to related species, could be used to predict which plants should be quarantined. We provide the first multi-species comparison of size and fecundity of invasive versus non-invasive plants in their native range. We find that invasive species are larger. Greater size yields greater fecundity, but we also find that invasives are more fecund per-unit-size.
Abstract.
Weegman MD, Fox AD, Bearhop S, Hilton GM, Walsh AJ, Cleasby IR, Hodgson DJ (2015). No evidence for sex bias in winter inter-site movements in an Arctic-nesting goose population.
Ibis,
157(2), 401-405.
Abstract:
No evidence for sex bias in winter inter-site movements in an Arctic-nesting goose population
Understanding movement of individuals between sites is necessary to quantify emigration and immigration, yet previous analyses exploring sex biases in site fidelity among birds have not evaluated remigration (the return of marked birds that moved to alternative areas from the site at which they were marked). Using novel Bayesian multistate models, we tested whether between-winter emigration, remigration and survival rates were sex-biased among 851 Greenland White-fronted Geese Anser albifrons flavirostris marked at Wexford, Ireland. We found no evidence for sex biases in emigration, remigration or survival. Thus, sex biases in winter site fidelity do not occur in any form in this population; these techniques for modelling sex-biased movement will be useful for a better understanding of site fidelity and connectivity in other marked animal populations.
Abstract.
Weegman MD, Fox AD, Bearhop S, Hilton GM, Walsh AJ, Cleasby IR, Hodgson DJ (2015). No evidence for sex bias in winter inter-site movements in an Arctic-nesting goose population. Ibis
Scales KL, Miller PI, Varo-Cruz N, Hodgson DJ, Hawkes LA, Godley BJ (2015). Oceanic loggerhead turtles Caretta caretta associate with thermal fronts: Evidence from the Canary Current Large Marine Ecosystem.
Marine Ecology Progress Series,
519, 195-207.
Abstract:
Oceanic loggerhead turtles Caretta caretta associate with thermal fronts: Evidence from the Canary Current Large Marine Ecosystem
Oceanographic fronts are physical interfaces between water masses that differ in properties such as temperature, salinity, turbidity and chlorophyll a enrichment. Bio-physical coupling along fronts can lead to the development of pelagic biodiversity hotspots. A diverse range of marine vertebrates have been shown to associate with fronts, using them as foraging and migration habitats. Elucidation of the ecological significance of fronts generates a better understanding of marine ecosystem functioning, conferring opportunities to improve management of anthropogenic activities in the oceans. This study presents novel insights into the oceanographic drivers of habitat use in a population of marine turtles characterised by an oceanic-neritic foraging dichotomy. Using satellite tracking data from adult female loggerhead turtles Caretta caretta nesting at Cape Verde (n = 12), we tested the hypothesis that oceanic-foraging loggerheads associate with mesocale (10s to 100s of km) thermal fronts. We used high-resolution (1 km) composite front mapping to characterise frontal activity in the Canary Current Large Marine Ecosystem over 2 temporal scales: (1) seasonal front frequency and (2) 7 d front metrics. Our use-availability analysis indicated that oceanic loggerheads show a preference for the highly productive upwelling region between Cape Verde and mainland Africa, an area of intense frontal activity. Within the upwelling region, turtles appear to forage epipelagically around mesoscale thermal fronts, exploiting profitable foraging opportunities resulting from physical aggregation of prey.
Abstract.
Mcdonald JL, Maclean M, Evans MR, Hodgson DJ (2015). Reconciling actual and perceived rates of predation by domestic cats.
Ecology and EvolutionAbstract:
Reconciling actual and perceived rates of predation by domestic cats
The predation of wildlife by domestic cats (Felis catus) is a complex problem: Cats are popular companion animals in modern society but are also acknowledged predators of birds, herpetofauna, invertebrates, and small mammals. A comprehensive understanding of this conservation issue demands an understanding of both the ecological consequence of owning a domestic cat and the attitudes of cat owners. Here, we determine whether cat owners are aware of the predatory behavior of their cats, using data collected from 86 cats in two UK villages. We examine whether the amount of prey their cat returns influences the attitudes of 45 cat owners toward the broader issue of domestic cat predation. We also contribute to the wider understanding of physiological, spatial, and behavioral drivers of prey returns among cats. We find an association between actual prey returns and owner predictions at the coarse scale of predatory/nonpredatory behavior, but no correlation between the observed and predicted prey-return rates among predatory cats. Cat owners generally disagreed with the statement that cats are harmful to wildlife, and disfavored all mitigation options apart from neutering. These attitudes were uncorrelated with the predatory behavior of their cats. Cat owners failed to perceive the magnitude of their cats' impacts on wildlife and were not influenced by ecological information. Management options for the mitigation of cat predation appear unlikely to work if they focus on "predation awareness" campaigns or restrictions of cat freedom.
Abstract.
Hodgson D, McDonald JL, Hosken DJ (2015). Resilience is Complicated, but Comparable: a Reply to Yeung and Richardson. Trends in Ecology and Evolution
Hooftman DAP, Bullock JM, Morley K, Lamb C, Hodgson DJ, Bell P, Thomas J, Hails RS (2015). Seed bank dynamics govern persistence of Brassica hybrids in crop and natural habitats.
Ann Bot,
115(1), 147-157.
Abstract:
Seed bank dynamics govern persistence of Brassica hybrids in crop and natural habitats.
BACKGROUND AND AIMS: Gene flow from crops to their wild relatives has the potential to alter population growth rates and demography of hybrid populations, especially when a new crop has been genetically modified (GM). This study introduces a comprehensive approach to assess this potential for altered population fitness, and uses a combination of demographic data in two habitat types and mathematical (matrix) models that include crop rotations and outcrossing between parental species. METHODS: Full life-cycle demographic rates, including seed bank survival, of non-GM Brassica rapa × B. napus F1 hybrids and their parent species were estimated from experiments in both agricultural and semi-natural habitats. Altered fitness potential was modelled using periodic matrices including crop rotations and outcrossing between parent species. KEY RESULTS: the demographic vital rates (i.e. for major stage transitions) of the hybrid population were intermediate between or lower than both parental species. The population growth rate (λ) of hybrids indicated decreases in both habitat types, and in a semi-natural habitat hybrids became extinct at two sites. Elasticity analyses indicated that seed bank survival was the greatest contributor to λ. In agricultural habitats, hybrid populations were projected to decline, but with persistence times up to 20 years. The seed bank survival rate was the main driver determining persistence. It was found that λ of the hybrids was largely determined by parental seed bank survival and subsequent replenishment of the hybrid population through outcrossing of B. rapa with B. napus. CONCLUSIONS: Hybrid persistence was found to be highly dependent on the seed bank, suggesting that targeting hybrid seed survival could be an important management option in controlling hybrid persistence. For local risk mitigation, an increased focus on the wild parent is suggested. Management actions, such as control of B. rapa, could indirectly reduce hybrid populations by blocking hybrid replenishment.
Abstract.
Author URL.
Salguero-Gómez R, Jones OR, Archer CR, Buckley YM, Che-Castaldo J, Caswell H, Hodgson D, Scheuerlein A, Conde DA, Brinks E, et al (2015). The compadre Plant Matrix Database: an open online repository for plant demography.
Journal of Ecology,
103(1), 202-218.
Abstract:
The compadre Plant Matrix Database: an open online repository for plant demography
Summary: Schedules of survival, growth and reproduction are key life-history traits. Data on how these traits vary among species and populations are fundamental to our understanding of the ecological conditions that have shaped plant evolution. Because these demographic schedules determine population growth or decline, such data help us understand how different biomes shape plant ecology, how plant populations and communities respond to global change and how to develop successful management tools for endangered or invasive species. Matrix population models summarize the life cycle components of survival, growth and reproduction, while explicitly acknowledging heterogeneity among classes of individuals in the population. Matrix models have comparable structures, and their emergent measures of population dynamics, such as population growth rate or mean life expectancy, have direct biological interpretations, facilitating comparisons among populations and species. Thousands of plant matrix population models have been parameterized from empirical data, but they are largely dispersed through peer-reviewed and grey literature, and thus remain inaccessible for synthetic analysis. Here, we introduce the compadre Plant Matrix Database version 3.0, an open-source online repository containing 468 studies from 598 species world-wide (672 species hits, when accounting for species studied in more than one source), with a total of 5621 matrices. compadre also contains relevant ancillary information (e.g. ecoregion, growth form, taxonomy, phylogeny) that facilitates interpretation of the numerous demographic metrics that can be derived from the matrices. Synthesis. Large collections of data allow broad questions to be addressed at the global scale, for example, in genetics (genbank), functional plant ecology (try, bien, d3) and grassland community ecology (nutnet). Here, we present compadre, a similarly data-rich and ecologically relevant resource for plant demography. Open access to this information, its frequent updates and its integration with other online resources will allow researchers to address timely and important ecological and evolutionary questions. Synthesis: Large collections of data sets allow broad questions to be addressed at the global scale, for example, in genetics (genbank), functional plant ecology (try, bien, d3) and grassland community ecology (nutnet). Here, we present compadre, a similarly data-rich and ecologically relevant resource for plant demography. Open access to this information, its frequent updates and its integration with other online resources will allow researchers to address timely and important ecological and evolutionary questions.
Abstract.
Guiver C, Dreiwi H, Filannino D-M, Hodgson D, Lloyd S, Townley S (2015). The role of population inertia in predicting the outcome of stage-structured biological invasions.
Math Biosci,
265, 1-11.
Abstract:
The role of population inertia in predicting the outcome of stage-structured biological invasions.
Deterministic dynamic models for coupled resident and invader populations are considered with the purpose of finding quantities that are effective at predicting when the invasive population will become established asymptotically. A key feature of the models considered is the stage-structure, meaning that the populations are described by vectors of discrete developmental stage- or age-classes. The vector structure permits exotic transient behaviour-phenomena not encountered in scalar models. Analysis using a linear Lyapunov function demonstrates that for the class of population models considered, a large so-called population inertia is indicative of successful invasion. Population inertia is an indicator of transient growth or decline. Furthermore, for the class of models considered, we find that the so-called invasion exponent, an existing index used in models for invasion, is not always a reliable comparative indicator of successful invasion. We highlight these findings through numerical examples and a biological interpretation of why this might be the case is discussed.
Abstract.
Author URL.
Hodgson D, McDonald JL, Hosken DJ (2015). What do you mean, 'resilient'?.
Trends in Ecology and EvolutionAbstract:
What do you mean, 'resilient'?
In a world beset by environmental disasters and anthropogenic disturbances, resilience might be the key to the persistence of natural systems. Yet, the 'measurement' of resilience is hampered by the multiple (and often conflicting) processes that yield the response of systems to insult. We recommend the simultaneous consideration of 'resistance' and 'recovery' as measurable components that together represent resilience.
Abstract.
Benton CH, Delahay RJ, Trewby H, Hodgson DJ (2015). What has molecular epidemiology ever done for wildlife disease research? Past contributions and future directions.
European Journal of Wildlife Research,
61(1), 1-16.
Abstract:
What has molecular epidemiology ever done for wildlife disease research? Past contributions and future directions
The increasing availability of novel molecular techniques has transformed the study of human health and disease epidemiology. However, uptake of such approaches has been more conservative in the field of wildlife disease epidemiology. We consider the reasons for this and discuss current and potential applications of molecular techniques in a variety of relevant areas within the field of wildlife disease research. These include conducting wildlife disease surveillance, identifying sources of pathogen emergence, uncovering host-pathogen dynamics and managing current outbreaks, including the development and monitoring of wildlife vaccines. We highlight key examples of applications of molecular epidemiological approaches to wildlife disease scenarios and draw parallels from human disease research to suggest potential future directions. The potential value of next generation sequencing technologies to the field of wildlife disease research is discussed, and initial applications are highlighted, balanced against consideration of the challenges involved. Using a wide range of examples drawn from research into human, livestock and wildlife diseases, we demonstrate the value of using molecular epidemiological approaches at all scales of wildlife disease research, from pathogen strains circulating at a global scale to intra-individual host-pathogen dynamics. The potential future contribution of these technologies to the field of wildlife disease epidemiology is substantial. In particular, they are likely to play an increasingly important role in helping us to address a principal challenge in the management of wildlife diseases which is how to tease apart the transmission dynamics of complex multi-host systems in order to develop effective and sustainable interventions.
Abstract.
2014
Dowling AJ, Hodgson DJ (2014). An unbiased method for clustering bacterial effectors using host cellular phenotypes.
Appl Environ Microbiol,
80(3), 1185-1196.
Abstract:
An unbiased method for clustering bacterial effectors using host cellular phenotypes.
We present a novel method implementing unbiased high-content morphometric cell analysis to classify bacterial effector phenotypes. This clustering methodology represents a significant advance over more qualitative visual approaches and can also be used to classify, and therefore predict the likely function of, unknown effector genes from any microbial genome. As a proof of concept, we use this approach to investigate 23 genetic regions predicted to encode antimacrophage effectors located across the genome of the insect and human pathogen Photorhabdus asymbiotica. Statistical cluster analysis using multiple cellular measures categorized treated macrophage phenotypes into three major groups relating to their putative functionality: (i) adhesins, (ii) cytolethal toxins, and (iii) cytomodulating toxins. Further investigation into their effects on phagocytosis revealed that several effectors also modulate this function and that the nature of this modulation (increased or decreased phagocytosis) is linked to the phenotype cluster group. Categorizing potential functionalities in this way allows rapid functional follow-up of key candidates for more-directed cell biological or biochemical investigation. Such an unbiased approach to the classification of candidate effectors will be useful for describing virulence-related regions in a wide range of genomes and will be useful in assigning putative functions to the growing number of microbial genes whose function remains unclear from homology searching.
Abstract.
Author URL.
Doherty PD, Alfaro-Shigueto J, Hodgson DJ, Mangel JC, Witt MJ, Godley BJ (2014). Big catch, little sharks: Insight into Peruvian small-scale longline fisheries.
Ecology and Evolution,
4(12), 2375-2383.
Abstract:
Big catch, little sharks: Insight into Peruvian small-scale longline fisheries
Shark take, driven by vast demand for meat and fins, is increasing. We set out to gain insights into the impact of small-scale longline fisheries in Peru. Onboard observers were used to document catch from 145 longline fishing trips (1668 fishing days) originating from Ilo, southern Peru. Fishing effort is divided into two seasons: targeting dolphinfish (Coryphaena hippurus; December to February) and sharks (March to November). A total of 16,610 sharks were observed caught, with 11,166 identified to species level. of these, 70.6% were blue sharks (Prionace glauca), 28.4% short-fin mako sharks (Isurus oxyrinchus), and 1% were other species (including thresher (Alopias vulpinus), hammerhead (Sphyrna zygaena), porbeagle (Lamnus nasus), and other Carcharhinidae species (Carcharhinus brachyurus, Carcharhinus falciformis, Galeorhinus galeus). Mean ± SD catch per unit effort of 33.6 ± 10.9 sharks per 1000 hooks was calculated for the shark season and 1.9 ± 3.1 sharks per 1000 hooks were caught in the dolphinfish season. An average of 83.7% of sharks caught (74.7% blue sharks; 93.3% mako sharks) were deemed sexually immature and under the legal minimum landing size, which for species exhibiting k-selected life history traits can result in susceptibility to over exploitation. As these growing fisheries operate along the entire Peruvian coast and may catch millions of sharks per annum, we conclude that their continued expansion, along with ineffective legislative approaches resulting in removal of immature individuals, has the potential to threaten the sustainability of the fishery, its target species, and ecosystem. There is a need for additional monitoring and research to inform novel management strategies for sharks while maintaining fisher livelihoods. © 2014 the Authors.
Abstract.
Eager EA, Guiver C, Hodgson D, Rebarber R, Stott I, Townley S (2014). Bounds on the dynamics of sink populations with noisy immigration.
Theor Popul Biol,
92, 88-96.
Abstract:
Bounds on the dynamics of sink populations with noisy immigration.
Sink populations are doomed to decline to extinction in the absence of immigration. The dynamics of sink populations are not easily modelled using the standard framework of per capita rates of immigration, because numbers of immigrants are determined by extrinsic sources (for example, source populations, or population managers). Here we appeal to a systems and control framework to place upper and lower bounds on both the transient and future dynamics of sink populations that are subject to noisy immigration. Immigration has a number of interpretations and can fit a wide variety of models found in the literature. We apply the results to case studies derived from published models for Chinook salmon (Oncorhynchus tshawytscha) and blowout penstemon (Penstemon haydenii).
Abstract.
Author URL.
Stokes KL, Fuller WJ, Glen F, Godley BJ, Hodgson DJ, Rhodes KA, Snape RTE, Broderick AC (2014). Detecting green shoots of recovery: the importance of long-term individual-based monitoring of marine turtles.
Animal Conservation,
17(6), 593-602.
Abstract:
Detecting green shoots of recovery: the importance of long-term individual-based monitoring of marine turtles
Population monitoring is an essential part of evaluating the effectiveness of management interventions for conservation. Coastal breeding aggregations of marine vertebrate species that come ashore to pup or nest provide an opportunistic window of observation into otherwise widely dispersed populations. Green turtle (Chelonia mydas) nesting on the north and west coasts of northern Cyprus has been monitored consistently and exhaustively since 1993, with an intensive saturation tagging programme running at one key site for the same duration. This historically depleted nesting population is showing signs of recovery, possibly in response to nest protection approaching two decades, with increasing nest numbers and rising levels of recruitment. Strong correlation between year-to-year magnitude of nesting and the proportion of new breeders in the nesting cohort implies that recruitment of new individuals to the breeding population is an important driver of this recovery trend. Recent changes in fishing activities may be impacting the local juvenile neritic stage, however, which may hinder this potential recovery. Individuals returning to breed after two years laid fewer clutches than those returning after three or four years, demonstrating a trade-off between remigration interval and breeding output. Average clutch frequencies have remained stable around a median of three clutches a year per female despite the demographic shift towards new nesters, which typically lay fewer clutches in their first season. We show that where local fecundity has been adequately assessed, the use of average clutch frequencies can be a reliable method for deriving nester abundance from nest counts. Index sites where individual-based monitoring is possible will be important in monitoring long-term climate driven changes in reproductive rates.
Abstract.
McDonald JL, Smith GC, McDonald RA, Delahay RJ, Hodgson D (2014). Mortality trajectory analysis reveals the drivers of sex-specific epidemiology in natural wildlife-disease interactions.
Proc Biol Sci,
281(1790).
Abstract:
Mortality trajectory analysis reveals the drivers of sex-specific epidemiology in natural wildlife-disease interactions.
In animal populations, males are commonly more susceptible to disease-induced mortality than females. However, three competing mechanisms can cause this sex bias: weak males may simultaneously be more prone to exposure to infection and mortality; being 'male' may be an imperfect proxy for the underlying driver of disease-induced mortality; or males may experience increased severity of disease-induced effects compared with females. Here, we infer the drivers of sex-specific epidemiology by decomposing fixed mortality rates into mortality trajectories and comparing their parameters. We applied Bayesian survival trajectory analysis to a 22-year longitudinal study of a population of badgers (Meles meles) naturally infected with bovine tuberculosis (bTB). At the point of infection, infected male and female badgers had equal mortality risk, refuting the hypothesis that acquisition of infection occurs in males with coincidentally high mortality. Males and females exhibited similar levels of heterogeneity in mortality risk, refuting the hypothesis that maleness is only a proxy for disease susceptibility. Instead, sex differences were caused by a more rapid increase in male mortality rates following infection. Males are indeed more susceptible to bTB, probably due to immunological differences between the sexes. We recommend this mortality trajectory approach for the study of infection in animal populations.
Abstract.
Author URL.
Guiver C, Hodgson D, Townley S (2014). Positive state controllability of positive linear systems.
Systems and Control Letters,
65(1), 23-29.
Abstract:
Positive state controllability of positive linear systems
Controllability of positive systems by positive inputs arises naturally in applications where both external and internal variables must remain positive for all time. In many applications, particularly in population biology, the need for positive inputs is often overly restrictive. Relaxing this requirement, the notion of positive state controllability of positive systems is introduced. A connection between positive state controllability and positive input controllability of a related system is established and used to obtain Kalman-like controllability criteria. In doing so we aim to encourage further study in this underdeveloped area. © 2013 Elsevier B.V. All rights reserved.
Abstract.
Dunstan DJ, Hodgson DJ (2014). Snails home.
Physica Scripta,
89(6).
Abstract:
Snails home
Many gardeners and horticulturalists seek non-chemical methods to control populations of snails. It has frequently been reported that snails that are marked and removed from a garden are later found in the garden again. This phenomenon is often cited as evidence for a homing instinct. We report a systematic study of the snail population in a small suburban garden, in which large numbers of snails were marked and removed over a period of about 6 months. While many returned, inferring a homing instinct from this evidence requires statistical modelling. Monte Carlo techniques demonstrate that movements of snails are better explained by drift under the influence of a homing instinct than by random diffusion. Maximum likelihood techniques infer the existence of two groups of snails in the garden: members of a larger population that show little affinity to the garden itself, and core members of a local garden population that regularly return to their home if removed. The data are strongly suggestive of a homing instinct, but also reveal that snail-throwing can work as a pest management strategy. © 2014 the Royal Swedish Academy of Sciences.
Abstract.
O'Brien S, Hodgson DJ, Buckling A (2014). Social evolution of toxic metal bioremediation in Pseudomonas aeruginosa.
Proc Biol Sci,
281(1787).
Abstract:
Social evolution of toxic metal bioremediation in Pseudomonas aeruginosa.
Bacteria are often iron-limited, and hence produce extracellular iron-scavenging siderophores. A crucial feature of siderophore production is that it can be an altruistic behaviour (individually costly but benefitting neighbouring cells), thus siderophore producers can be invaded by non-producing social 'cheats'. Recent studies have shown that siderophores can also bind other heavy metals (such as Cu and Zn), but in this case siderophore chelation actually reduces metal uptake by bacteria. These complexes reduce heavy metal toxicity, hence siderophore production may contribute to toxic metal bioremediation. Here, we show that siderophore production in the context of bioremediation is also an altruistic trait and can be exploited by cheating phenotypes in the opportunistic pathogen Pseudomonas aeruginosa. Specifically, we show that in toxic copper concentrations (i) siderophore non-producers evolve de novo and reach high frequencies, and (ii) producing strains are fitter than isogenic non-producing strains in monoculture, and vice versa in co-culture. Moreover, we show that the evolutionary effect copper has on reducing siderophore production is greater than the reduction observed under iron-limited conditions. We discuss the relevance of these results to the evolution of siderophore production in natural communities and heavy metal bioremediation.
Abstract.
Author URL.
Neenan STV, Hodgson DJ, Tregenza T, Boothroyd D, Ellis CD (2014). The suitability of VIE tags to assess stock enhancement success in juvenile European lobsters (Homarus gammarus).
Aquaculture ResearchAbstract:
The suitability of VIE tags to assess stock enhancement success in juvenile European lobsters (Homarus gammarus)
Assessments of stock enhancement programmes for European lobsters (Homarus gammarus) require mark-recapture analysis of stocked individuals. However, established tag technology is deemed unsuitable for extensive use by many current lobster hatcheries, particularly upon the early juvenile stages. We tested the suitability of fluorescent Visible Implant Elastomer (VIE) tags for use in 5-month-old juvenile lobsters. Three treatment groups comprising 348 cultured lobsters in total were used to examine survival, growth and tag retention, and to assess mobility, shelter use and moulting behaviours. Tagging had no significant effect on lobster survival, growth, mobility, shelter use or moult frequency. Survival over 7 weeks was 75% among lobsters tagged with two elastomers, 76% in those with one elastomer and 74% among untagged controls. Mortality during moulting did not increase in tagged (6%) compared to untagged lobsters (9%). We found no evidence that VIE tags cause any negative effects that would be expected to inhibit survival upon wild release, but tag loss had reached 12% in both tagged treatments after 7 weeks and showed no sign of abating. Our study suggests that VIEs effectiveness in discerning cultured lobsters long after wild release may be limited when used in smaller juveniles. © 2014 John Wiley & Sons Ltd.
Abstract.
Hodgson DJ, Hosken DJ (2014). Ultimate and proximate functions of sperm RNA: a reply to Holman and Price.
Trends Ecol Evol,
29(12).
Author URL.
Benton CH, Delahay RJ, Trewby H, Hodgson DJ (2014). What has molecular epidemiology ever done for wildlife disease research? Past contributions and future directions. European Journal of Wildlife Research
Hosken DJ, Hodgson DJ (2014). Why do sperm carry RNA? Relatedness, conflict, and control.
Trends in Ecology and Evolution,
29(8), 451-455.
Abstract:
Why do sperm carry RNA? Relatedness, conflict, and control
Classically, sperm were seen as transcriptionally inactive vehicles for delivering the paternal haplotype to an egg. Yet, it has become apparent that sperm also carry thousands of different RNAs, and the functions of most of these are unknown. Here, we make four novel suggestions for sperm RNA function. First, they could act as relatedness markers facilitating sperm cooperation. Second, they could act as paternally imposed suppressors of haploid interests. Third, they could act as a nuptial gift, providing the female with resources that entice her to fertilise ova using the sperm of the gift-provider. Fourth, they could represent the contents of a Trojan horse, delivered by males to manipulate female reproduction. We discuss these ideas and suggest how they might be tested. © 2014 the Authors.
Abstract.
Hosken DJ, Hodgson DJ (2014). Why do sperm carry RNA? Relatedness, conflict, and control.
Trends Ecol Evol,
29(8), 451-455.
Abstract:
Why do sperm carry RNA? Relatedness, conflict, and control.
Classically, sperm were seen as transcriptionally inactive vehicles for delivering the paternal haplotype to an egg. Yet, it has become apparent that sperm also carry thousands of different RNAs, and the functions of most of these are unknown. Here, we make four novel suggestions for sperm RNA function. First, they could act as relatedness markers facilitating sperm cooperation. Second, they could act as paternally imposed suppressors of haploid interests. Third, they could act as a nuptial gift, providing the female with resources that entice her to fertilise ova using the sperm of the gift-provider. Fourth, they could represent the contents of a Trojan horse, delivered by males to manipulate female reproduction. We discuss these ideas and suggest how they might be tested.
Abstract.
Author URL.
2013
Harrison XA, Hodgson DJ, Inger R, Colhoun K, Gudmundsson GA, McElwaine G, Tregenza T, Bearhop S (2013). Environmental conditions during breeding modify the strength of mass-dependent carry-over effects in a migratory bird.
PLoS One,
8(10).
Abstract:
Environmental conditions during breeding modify the strength of mass-dependent carry-over effects in a migratory bird.
In many animals, processes occurring in one season carry over to influence reproductive success and survival in future seasons. The strength of such carry-over effects is unlikely to be uniform across years, yet our understanding of the processes that are capable of modifying their strength remains limited. Here we show that female light-bellied Brent geese with higher body mass prior to spring migration successfully reared more offspring during breeding, but only in years where environmental conditions during breeding were favourable. In years of bad weather during breeding, all birds suffered reduced reproductive output irrespective of pre-migration mass. Our results suggest that the magnitude of reproductive benefits gained by maximising body stores to fuel breeding fluctuates markedly among years in concert with conditions during the breeding season, as does the degree to which carry-over effects are capable of driving variance in reproductive success among individuals. Therefore while carry-over effects have considerable power to drive fitness asymmetries among individuals, our ability to interpret these effects in terms of their implications for population dynamics is dependent on knowledge of fitness determinants occurring in subsequent seasons.
Abstract.
Author URL.
Leggett HC, Benmayor R, Hodgson DJ, Buckling A (2013). Experimental evolution of adaptive phenotypic plasticity in a parasite.
Current Biology,
23(2), 139-142.
Abstract:
Experimental evolution of adaptive phenotypic plasticity in a parasite
Coinfection of parasite genotypes can select for various changes in parasite life history strategies relative to single genotype infections, with consequences for disease dynamics and severity [1-14]. However, even where coinfection is common, a parasite genotype is also likely to regularly experience single genotype infections over relatively short periods of evolutionary time, due to chance, changes in local disease transmission, and parasite population structuring. Such alternating conditions between single genotype and coinfections will impose conflicting pressures on parasites, potentially selecting for facultative responses to coinfection [14-19]. Although such adaptive phenotypic plasticity in response to social environment has been observed in protozoan parasites and viruses [20, 21], here we show it evolving in real time in response to coinfection under conditions in which both single infections and coinfections are common. We experimentally evolved an obligate-killing virus under conditions of single virus infections (single lines) or a mix of single infections and coinfections (mixed lines) and found mixed lines to evolve a plastic lysis time: they killed host cells more rapidly when coinfecting than when infecting alone. This behavior resulted in high fitness under both infection conditions. Such plasticity has important consequences for the epidemiology of infectious diseases and the evolution of cooperation. © 2013 Elsevier Ltd all rights reserved.
Abstract.
Leggett HC, Benmayor R, Hodgson DJ, Buckling A (2013). Experimental evolution of adaptive phenotypic plasticity in a parasite.
Curr Biol,
23(2), 139-142.
Abstract:
Experimental evolution of adaptive phenotypic plasticity in a parasite.
Coinfection of parasite genotypes can select for various changes in parasite life history strategies relative to single genotype infections, with consequences for disease dynamics and severity. However, even where coinfection is common, a parasite genotype is also likely to regularly experience single genotype infections over relatively short periods of evolutionary time, due to chance, changes in local disease transmission, and parasite population structuring. Such alternating conditions between single genotype and coinfections will impose conflicting pressures on parasites, potentially selecting for facultative responses to coinfection. Although such adaptive phenotypic plasticity in response to social environment has been observed in protozoan parasites and viruses, here we show it evolving in real time in response to coinfection under conditions in which both single infections and coinfections are common. We experimentally evolved an obligate-killing virus under conditions of single virus infections (single lines) or a mix of single infections and coinfections (mixed lines) and found mixed lines to evolve a plastic lysis time: they killed host cells more rapidly when coinfecting than when infecting alone. This behavior resulted in high fitness under both infection conditions. Such plasticity has important consequences for the epidemiology of infectious diseases and the evolution of cooperation.
Abstract.
Author URL.
Sutherland WJ, Freckleton RP, Godfray HCJ, Beissinger SR, Benton T, Cameron DD, Carmel Y, Coomes DA, Coulson T, Emmerson MC, et al (2013). Identification of 100 fundamental ecological questions.
Journal of Ecology,
101(1), 58-67.
Abstract:
Identification of 100 fundamental ecological questions
Fundamental ecological research is both intrinsically interesting and provides the basic knowledge required to answer applied questions of importance to the management of the natural world. The 100th anniversary of the British Ecological Society in 2013 is an opportune moment to reflect on the current status of ecology as a science and look forward to high-light priorities for future work. To do this, we identified 100 important questions of fundamental importance in pure ecology. We elicited questions from ecologists working across a wide range of systems and disciplines. The 754 questions submitted (listed in the online appendix) from 388 participants were narrowed down to the final 100 through a process of discussion, rewording and repeated rounds of voting. This was done during a two-day workshop and thereafter. The questions reflect many of the important current conceptual and technical pre-occupations of ecology. For example, many questions concerned the dynamics of environmental change and complex ecosystem interactions, as well as the interaction between ecology and evolution. The questions reveal a dynamic science with novel subfields emerging. For example, a group of questions was dedicated to disease and micro-organisms and another on human impacts and global change reflecting the emergence of new subdisciplines that would not have been foreseen a few decades ago. The list also contained a number of questions that have perplexed ecologists for decades and are still seen as crucial to answer, such as the link between population dynamics and life-history evolution. Synthesis. These 100 questions identified reflect the state of ecology today. Using them as an agenda for further research would lead to a substantial enhancement in understanding of the discipline, with practical relevance for the conservation of biodiversity and ecosystem function. © 2013 the Authors. Journal of Ecology © 2013 British Ecological Society.
Abstract.
Fuller WJ, Godley BJ, Hodgson DJ, Reece SE, Witt MJ, Broderick AC (2013). Importance of spatio-temporal data for predicting the effects of climate change on marine turtle sex ratios.
Marine Ecology Progress Series,
488, 267-274.
Abstract:
Importance of spatio-temporal data for predicting the effects of climate change on marine turtle sex ratios
Species with temperature-dependent sex determination (TSD) are likely to be impacted by climate change. There is a paucity of data on the contemporary sex ratios of offspring produced by regional marine turtle populations. The lack of such information inhibits the ability of researchers to accurately predict how future meteorological and climate-driven changes may affect turtle populations. Moreover, these data are integral for the development of regional and global recovery plans for declining turtle populations. We estimate offspring sex ratios for the loggerhead turtle Caretta caretta at a range of beaches on the Mediterranean island of Cyprus over a 10 yr period (1997 to 2006; 40 beaches, 628 clutches, 29402 hatchlings). Based on hatchling sex determination, we found the pivotal incubation temperature (the temperature at which a 50:50 sex ratio occurs) to be 28.9°C, and the pivotal incubation duration to be 56.3 d. From the incubation durations of over 628 in situ clutches laid on different beaches, we estimate that 89% of the offspring produced from these clutches were female. There was, however, both inter-annual (74 to 95% female) and inter-beach (58-98% female) variability in mean offspring sex ratios. These findings highlight the need for wide-scale, long-term monitoring of primary sex ratios in order to accurately predict the likely impacts of climate change. Despite spatial and temporal variation in offspring sex ratios produced, male hatchlings are certainly in the minority in Cyprus. It is therefore highly likely that beaches producing males will become increasingly critical habitats for successful clutch incubation in the face of predicted rising temperatures. © Inter-Research 2013.
Abstract.
Mills CA, Dawson DA, Horsburgh GJ, Godley BJ, Hodgson DJ (2013). Isolation and characterisation of hazel dormouse (Muscardinus avellanarius) microsatellite loci.
Conservation Genetics Resources,
5(3), 687-692.
Abstract:
Isolation and characterisation of hazel dormouse (Muscardinus avellanarius) microsatellite loci
Hazel dormice, Muscardinus avellanarius (Rodentia: Gliridae) are vulnerable to habitat loss and fragmentation, and thus protected by European Directives. We isolated hazel dormouse microsatellite sequences from enriched genomic libraries to facilitate conservation-focussed research, such as population genetics, regarding this threatened species. Fifty-three primer sets were designed from 51 newly isolated loci. Additionally, we redesigned and tested nine primer sets from previously-published hazel dormouse microsatellite sequences. These 62 marker sets were initially tested in eight unrelated individuals. Thirty-nine loci, which were polymorphic and amplified in >88 % of these samples (extracted from hair), were then genotyped and characterised in 22-26 individuals. of these, 26 autosomal loci (18 new and eight published) adhered to Hardy-Weinberg equilibrium (p ≤ 0.05) and displayed an estimated null allele frequency of
Abstract.
Smee MR, Pauchet Y, Wilkinson P, Wee B, Singer MC, ffrench-Constant RH, Hodgson DJ, Mikheyev AS (2013). Microsatellites for the marsh fritillary butterfly: de novo transcriptome sequencing, and a comparison with amplified fragment length polymorphism (AFLP) markers.
PLoS One,
8(1).
Abstract:
Microsatellites for the marsh fritillary butterfly: de novo transcriptome sequencing, and a comparison with amplified fragment length polymorphism (AFLP) markers.
BACKGROUND: Until recently the isolation of microsatellite markers from Lepidoptera has proved troublesome, expensive and time-consuming. Following on from a previous study of Edith's checkerspot butterfly, Euphydryas editha, we developed novel microsatellite markers for the vulnerable marsh fritillary butterfly, E. aurinia. Our goal was to optimize the process in order to reduce both time and cost relative to prevailing techniques. This was accomplished by using a combination of previously developed techniques: in silico mining of a de novo assembled transcriptome sequence, and genotyping the microsatellites found there using an economic method of fluorescently labelling primers. PRINCIPAL FINDINGS: in total, we screened nine polymorphic microsatellite markers, two of which were previously published, and seven that were isolated de novo. These markers were able to amplify across geographically isolated populations throughout Continental Europe and the UK. Significant deviations from Hardy-Weinberg equilibrium were evident in some populations, most likely due to the presence of null alleles. However, we used an F(st) outlier approach to show that these markers are likely selectively neutral. Furthermore, using a set of 128 individuals from 11 populations, we demonstrate consistency in population differentiation estimates with previously developed amplified fragment length polymorphism (AFLP) markers (r = 0.68, p
Abstract.
Author URL.
Graham J, Smith GC, Delahay RJ, Bailey T, McDonald RA, Hodgson D (2013). Multi-state modelling reveals sex-dependent transmission, progression and severity of tuberculosis in wild badgers.
Epidemiol Infect,
141(7), 1429-1436.
Abstract:
Multi-state modelling reveals sex-dependent transmission, progression and severity of tuberculosis in wild badgers.
Statistical models of epidemiology in wildlife populations usually consider diseased individuals as a single class, despite knowledge that infections progress through states of severity. Bovine tuberculosis (bTB) is a serious zoonotic disease threatening the UK livestock industry, but we have limited understanding of key epidemiological processes in its wildlife reservoirs. We estimated differential survival, force of infection and progression in disease states in a population of Eurasian badgers (Meles meles), naturally infected with bTB. Our state-dependent models overturn prevailing categorizations of badger disease states, and find novel evidence for early onset of disease-induced mortality in male but not female badgers. Males also have higher risk of infection and more rapid disease progression which, coupled with state-dependent increases in mortality, could promote sex biases in the risk of transmission to cattle. Our results reveal hidden complexities in wildlife disease epidemiology, with implications for the management of TB and other zoonotic diseases.
Abstract.
Author URL.
Evans MR, Bithell M, Cornell SJ, Dall SRX, Díaz S, Emmott S, Ernande B, Grimm V, Hodgson DJ, Lewis SL, et al (2013). Predictive systems ecology.
Proceedings. Biological sciences / the Royal Society,
280(1771).
Abstract:
Predictive systems ecology
Human societies, and their well-being, depend to a significant extent on the state of the ecosystems that surround them. These ecosystems are changing rapidly usually in response to anthropogenic changes in the environment. To determine the likely impact of environmental change on ecosystems and the best ways to manage them, it would be desirable to be able to predict their future states. We present a proposal to develop the paradigm of predictive systems ecology, explicitly to understand and predict the properties and behaviour of ecological systems. We discuss the necessary and desirable features of predictive systems ecology models. There are places where predictive systems ecology is already being practised and we summarize a range of terrestrial and marine examples. Significant challenges remain but we suggest that ecology would benefit both as a scientific discipline and increase its impact in society if it were to embrace the need to become more predictive.
Abstract.
Evans MR, Bithell M, Cornell SJ, Dall SRX, Diaz S, Emmott S, Ernande B, Grimm V, Hodgson DJ, Lewis SL, et al (2013). Predictive systems ecology.
Proceedings of the Royal Society of London: Biological Sciences,
280(1771).
Abstract:
Predictive systems ecology
Human societies, and their well-being, depend to a significant extent on the state of the ecosystems that surround them. These ecosystems are changing rapidly usually in response to anthropogenic changes in the environment. To determine the likely impact of environmental change on ecosystems and the best ways to manage them, it would be desirable to be able to predict their future states. We present a proposal to develop the paradigm of Predictive Systems Ecology, explicitly to understand and predict the properties and behaviour of ecological systems. We discuss the necessary and desirable features of predictive systems ecology models. There are places where predictive systems ecology is already being practiced and we summarise a range of terrestrial and marine examples. Significant challenges remain but we suggest that ecology would benefit both as a scientific discipline and increase its impact in society if it were to embrace the need to become more predictive.
Abstract.
Evans MR, Bithell M, Cornell SJ, Dall SRX, Díaz S, Emmott S, Ernande B, Grimm V, Hodgson DJ, Lewis SL, et al (2013). Predictive systems ecology.
Proceedings. Biological sciences / the Royal Society,
280(1771).
Abstract:
Predictive systems ecology.
Human societies, and their well-being, depend to a significant extent on the state of the ecosystems that surround them. These ecosystems are changing rapidly usually in response to anthropogenic changes in the environment. To determine the likely impact of environmental change on ecosystems and the best ways to manage them, it would be desirable to be able to predict their future states. We present a proposal to develop the paradigm of predictive systems ecology, explicitly to understand and predict the properties and behaviour of ecological systems. We discuss the necessary and desirable features of predictive systems ecology models. There are places where predictive systems ecology is already being practised and we summarize a range of terrestrial and marine examples. Significant challenges remain but we suggest that ecology would benefit both as a scientific discipline and increase its impact in society if it were to embrace the need to become more predictive.
Abstract.
House CM, Lewis Z, Hodgson DJ, Wedell N, Sharma MD, Hunt J, Hosken DJ (2013). Sexual and natural selection both influence male genital evolution.
PLoS One,
8(5).
Abstract:
Sexual and natural selection both influence male genital evolution.
Rapid and divergent evolution of male genital morphology is a conspicuous and general pattern across internally fertilizing animals. Rapid genital evolution is thought to be the result of sexual selection, and the role of natural selection in genital evolution remains controversial. However, natural and sexual selection are believed to act antagonistically on male genital form. We conducted an experimental evolution study to investigate the combined effects of natural and sexual selection on the genital-arch lobes of male Drosophila simulans. Replicate populations were forced to evolve under lifetime monogamy (relaxed sexual selection) or lifetime polyandry (elevated sexual selection) and two temperature regimes, 25°C (relaxed natural selection) or 27°C (elevated natural selection) in a fully factorial design. We found that natural and sexual selection plus their interaction caused genital evolution. Natural selection caused some aspects of genital form to evolve away from their sexually selected shape, whereas natural and sexual selection operated in the same direction for other shape components. Additionally, sexual and natural selection tended to favour larger genitals. Thus we find that the underlying selection driving genital evolution is complex, does not only involve sexual selection, and that natural selection and sexual selection do not always act antagonistically.
Abstract.
Author URL.
Somers-Yeates R, Hodgson D, McGregor PK, Spalding A, Ffrench-Constant RH (2013). Shedding light on moths: shorter wavelengths attract noctuids more than geometrids.
Biol Lett,
9(4).
Abstract:
Shedding light on moths: shorter wavelengths attract noctuids more than geometrids.
With moth declines reported across Europe, and parallel changes in the amount and spectra of street lighting, it is important to understand exactly how artificial lights affect moth populations. We therefore compared the relative attractiveness of shorter wavelength (SW) and longer wavelength (LW) lighting to macromoths. SW light attracted significantly more individuals and species of moth, either when used alone or in competition with LW lighting. We also found striking differences in the relative attractiveness of different wavelengths to different moth groups. SW lighting attracted significantly more Noctuidae than LW, whereas both wavelengths were equally attractive to Geometridae. Understanding the extent to which different groups of moth are attracted to different wavelengths of light will be useful in determining the impact of artificial light on moth populations.
Abstract.
Author URL.
Teacher AGF, Griffiths DJ, Hodgson DJ, Inger R (2013). Smartphones in ecology and evolution: a guide for the app-rehensive.
Ecology and Evolution,
3(16), 5268-5278.
Abstract:
Smartphones in ecology and evolution: a guide for the app-rehensive
Smartphones and their apps (application software) are now used by millions of people worldwide and represent a powerful combination of sensors, information transfer, and computing power that deserves better exploitation by ecological and evolutionary researchers. We outline the development process for research apps, provide contrasting case studies for two new research apps, and scan the research horizon to suggest how apps can contribute to the rapid collection, interpretation, and dissemination of data in ecology and evolutionary biology. We emphasize that the usefulness of an app relies heavily on the development process, recommend that app developers are engaged with the process at the earliest possible stage, and commend efforts to create open-source software scaffolds on which customized apps can be built by nonexperts. We conclude that smartphones and their apps could replace many traditional handheld sensors, calculators, and data storage devices in ecological and evolutionary research. We identify their potential use in the high-throughput collection, analysis, and storage of complex ecological information. Smartphones and their apps (application software) are now used by millions of people worldwide and represent a powerful combination of sensors, information transfer, and computing power that deserves better exploitation by ecological and evolutionary researchers. We outline the development process for research apps, provide contrasting case studies for two new research apps, and scan the research horizon to suggest how apps can contribute to the rapid collection, interpretation, and dissemination of data in ecology and evolutionary biology. © 2013 the Authors.
Abstract.
Pincheira-Donoso D, Tregenza T, Witt MJ, Hodgson DJ (2013). The evolution of viviparity opens opportunities for lizard radiation but drives it into a climatic cul-de-sac. Global Ecology and Biogeography
Pincheira-Donoso D, Tregenza T, Witt MJ, Hodgson DJ (2013). The evolution of viviparity opens opportunities for lizard radiation but drives it into a climatic cul-de-sac.
Global Ecology and Biogeography,
22(7), 857-867.
Abstract:
The evolution of viviparity opens opportunities for lizard radiation but drives it into a climatic cul-de-sac
Aim: Evolutionary radiations into novel areas or niches require innovative adaptations. However, rapid subsequent changes in these novel conditions might demand rapid re-adaptations to secure population persistence and prevent extinction. We propose that reptilian viviparity (live birth) is consistent with such a scenario. Using the Liolaemus lizard radiation, we investigate the hypotheses that historical invasions of cold climates have been permitted by transitions to viviparity, and that this parity mode is irreversible. Then, we investigate whether these combined factors restrict viviparous lizards to cold climates, and hence, whether viviparous species are particularly threatened by climate change. Location: South America. Methods: We employ phylogenetic analyses to investigate evolutionary transitions in reproductive modes and their consequences for environmental restrictions in viviparous lizards. We then employ climatic projections to predict the impact of climate change on the future persistence of these organisms. Results: the oviparity-to-viviparity transition is consistently associated with colonization of cold climates, and appears to be irreversible. Since viviparity seems less viable (compared with oviparity) in warm climates, species that evolve viviparity in cold climates are likely to remain adaptively constrained to such environments. Therefore, upward-poleward advances of climate warming will cause severe shifts and contractions of viviparous species ranges, threatening major extinctions over the next half century. Main conclusions: Viviparity has been largely responsible for the successful radiation of Liolaemus into cold climates, but since this adaptation is predominantly viable in these environments and is unlikely to re-evolve into oviparity, viviparity may prove to be an evolutionary dead-end for lizards facing rapid climate change. © 2013 John Wiley & Sons Ltd.
Abstract.
O'Brien S, Hodgson DJ, Buckling A (2013). The interplay between microevolution and community structure in microbial populations.
Current Opinion in Biotechnology,
24(4), 821-825.
Abstract:
The interplay between microevolution and community structure in microbial populations
The structure of microbial communities is key to their functionality. However, this structure is likely to be influenced by adaptive genetic change in members of the community, which can occur over a matter of days. Changes in community structure can in turn influence the evolutionary trajectories of species within the community, further altering community structure. Microbial communities provide evidence for this interplay between rapid evolution and community structure. To date, studies are primarily limited to simple in vitro systems, but we suggest similar processes are inevitably operating in both natural and derived communities, which are important for biotechnology. © 2013 Elsevier Ltd.
Abstract.
O'Brien S, Hodgson DJ, Buckling A (2013). The interplay between microevolution and community structure in microbial populations.
Curr Opin Biotechnol,
24(4), 821-825.
Abstract:
The interplay between microevolution and community structure in microbial populations.
The structure of microbial communities is key to their functionality. However, this structure is likely to be influenced by adaptive genetic change in members of the community, which can occur over a matter of days. Changes in community structure can in turn influence the evolutionary trajectories of species within the community, further altering community structure. Microbial communities provide evidence for this interplay between rapid evolution and community structure. To date, studies are primarily limited to simple in vitro systems, but we suggest similar processes are inevitably operating in both natural and derived communities, which are important for biotechnology.
Abstract.
Author URL.
Mangel JC, Alfaro-Shigueto J, Witt MJ, Hodgson DJ, Godley BJ (2013). Using pingers to reduce bycatch of small cetaceans in Peru's small-scale driftnet fishery.
ORYX,
47(4), 595-606.
Abstract:
Using pingers to reduce bycatch of small cetaceans in Peru's small-scale driftnet fishery
There is growing awareness that small-scale fisheries may have large impacts on threatened marine fauna. Bycatch of small cetaceans by the Peruvian small-scale driftnet fleet results in the deaths of thousands of animals annually. We sought to assess the effectiveness of acoustic alarms (pingers) for reducing the incidental capture of dolphins and porpoises by this fleet. Forty-three experimental trips (156 fishing sets) and 47 control trips (195 fishing sets) out of Salaverry Port, northern Peru, were observed from April 2009 to August 2011. Twenty-two percent of control sets captured small cetaceans (67 individuals) and 16% of experimental sets had captures of small cetaceans (33 individuals). The bycatch rate of experimental sets was 0.50 individuals km-2h-1, whereas for control sets the rate was 0.80 individuals km-2h-1. This 37% reduction in bycatch rate suggests that pingers may be effective in reducing the bycatch of small cetaceans in this fishery. Catch rates of the fishery's target shark and ray species were unchanged. Given the vast size of this fishery and its current levels of bycatch of small cetaceans (>Â 10,000 individuals annually), even the modest declines in bycatch we observed could result in reductions in mortality of hundreds or thousands of small cetaceans per annum. Challenges, including increased costs, to large-scale utilization of pingers have yet to be overcome. The harpooning of dolphins for use as bait will also need to be addressed for further reductions in dolphin and porpoise bycatch and mortality to be achievable. © 2013 Fauna & Flora International.
Abstract.
2012
Witt MJ, Sheehan EV, Bearhop S, Broderick AC, Conley DC, Cotterell SP, Crow E, Grecian WJ, Halsband C, Hodgson DJ, et al (2012). Assessing wave energy effects on biodiversity: the Wave Hub experience. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 370(1959), 502-529.
Witt MJ, Sheehan EV, Bearhop S, Broderick AC, Conley DC, Cotterell SP, Crow E, Grecian WJ, Halsband C, Hodgson DJ, et al (2012). Assessing wave energy effects on biodiversity: the Wave Hub experience.
Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences,
370(1959), 502-529.
Abstract:
Assessing wave energy effects on biodiversity: the Wave Hub experience
Marine renewable energy installations harnessing energy from wind, wave and tidal resources are likely to become a large part of the future energy mix worldwide. The potential to gather energy from waves has recently seen increasing interest, with pilot developments in several nations. Although technology to harness wave energy lags behind that of wind and tidal generation, it has the potential to contribute significantly to energy production. As wave energy technology matures and becomes more widespread, it is likely to result in further transformation of our coastal seas. Such changes are accompanied by uncertainty regarding their impacts on biodiversity. To date, impacts have not been assessed, as wave energy converters have yet to be fully developed. Therefore, there is a pressing need to build a framework of understanding regarding the potential impacts of these technologies, underpinned by methodologies that are transferable and scalable across sites to facilitate formal meta-analysis. We first review the potential positive and negative effects of wave energy generation, and then, with specific reference to our work at the Wave Hub (a wave energy test site in southwest England, UK), we set out the methodological approaches needed to assess possible effects of wave energy on biodiversity. We highlight the need for national and international research clusters to accelerate the implementation of wave energy, within a coherent understanding of potential effects-both positive and negative. © 2011 the Royal Society.
Abstract.
Stott I, Hodgson DJ, Townley S (2012). Beyond sensitivity: nonlinear perturbation analysis of transient dynamics.
METHODS IN ECOLOGY AND EVOLUTION,
3(4), 673-684.
Author URL.
Scott R, Hodgson DJ, Witt MJ, Coyne MS, Adnyana W, Blumenthal JM, Broderick AC, Canbolat AF, Catry P, Ciccione S, et al (2012). Global analysis of satellite tracking data shows that adult green turtles are significantly aggregated in Marine Protected Areas.
Global Ecology and Biogeography,
21(11), 1053-1061.
Abstract:
Global analysis of satellite tracking data shows that adult green turtles are significantly aggregated in Marine Protected Areas
Aim Tracking technologies are often proposed as a method to elucidate the complex migratory life histories of migratory marine vertebrates, allowing spatially explicit threats to be identified and mitigated. We conducted a global analysis of foraging areas of adult green turtles (Chelonia mydas) subject to satellite tracking (n= 145) and the conservation designation of these areas according to International Union for Conservation of Nature criteria. Location the green turtle has a largely circumtropical distribution, with adults migrating up to thousands of kilometres between nesting beaches and foraging areas, typically in neritic seagrass or algal beds. Methods We undertook an assessment of satellite tracking projects that followed the movements of green turtles in tropical and subtropical habitats. This approach was facilitated by the use of the Satellite Tracking and Analysis Tool (http://www.seaturtle.org) and the integration of publicly available data on Marine Protected Areas (MPAs). Results We show that turtles aggregate in designated MPAs far more than would be expected by chance when considered globally (35% of all turtles were located within MPAs) or separately by ocean basin (Atlantic 67%, Indian 34%, Mediterranean 19%, Pacific 16%). Furthermore, we show that the size, level of protection and time of establishment of MPAs affects the likelihood of MPAs containing foraging turtles, highlighting the importance of large, well-established reserves. Main conclusions Our findings constitute compelling evidence of the world-wide effectiveness of extant MPAs in circumscribing important foraging habitats for a marine megavertebrate. © 2012 Blackwell Publishing Ltd.
Abstract.
Scott R, Hodgson DJ, Witt MJ, Coyne MS, Blumenthal JM, Broderick AC, Richardson PB, Rees AF, Godley BJ, Coyne MS, et al (2012). Global analysis of satellite tracking data shows that adult green turtles are significantly aggregated in Marine Protected Areas.
Global Ecology and BiogeographyAbstract:
Global analysis of satellite tracking data shows that adult green turtles are significantly aggregated in Marine Protected Areas
Aim Tracking technologies are often proposed as a method to elucidate the complex migratory life histories of migratory marine vertebrates, allowing spatially explicit threats to be identified and mitigated. We conducted a global analysis of foraging areas of adult green turtles (Chelonia mydas) subject to satellite tracking (n= 145) and the conservation designation of these areas according to International Union for Conservation of Nature criteria. Location the green turtle has a largely circumtropical distribution, with adults migrating up to thousands of kilometres between nesting beaches and foraging areas, typically in neritic seagrass or algal beds. Methods We undertook an assessment of satellite tracking projects that followed the movements of green turtles in tropical and subtropical habitats. This approach was facilitated by the use of the Satellite Tracking and Analysis Tool () and the integration of publicly available data on Marine Protected Areas (MPAs). Results We show that turtles aggregate in designated MPAs far more than would be expected by chance when considered globally (35% of all turtles were located within MPAs) or separately by ocean basin (Atlantic 67%, Indian 34%, Mediterranean 19%, Pacific 16%). Furthermore, we show that the size, level of protection and time of establishment of MPAs affects the likelihood of MPAs containing foraging turtles, highlighting the importance of large, well-established reserves. Main conclusions Our findings constitute compelling evidence of the world-wide effectiveness of extant MPAs in circumscribing important foraging habitats for a marine megavertebrate. © 2012 Blackwell Publishing Ltd.
Abstract.
Blount JD, Rowland HM, Drijfhout FP, Endler JA, Inger R, Sloggett JJ, Hurst GDD, Hodgson DJ, Speed MP (2012). How the ladybird got its spots: Effects of resource limitation on the honesty of aposematic signals.
Functional Ecology,
26(2), 334-342.
Abstract:
How the ladybird got its spots: Effects of resource limitation on the honesty of aposematic signals
Prey species often possess defences (e.g. toxins) coupled with warning signals (i.e. aposematism). There is growing evidence that the expression of aposematic signals often varies within species and correlates with the strength of chemical defences. This has led to the speculation that such signals may be 'honest', with signal reliability ensured by the costliness of producing or maintaining aposematic traits. We reared larval seven-spot ladybirds (Coccinella septempunctata) on a Low or High aphid diet and measured the effects on warning signal expression (elytral carotenoid pigmentation, conspicuousness, spot size), levels of defensive alkaloids (precoccinelline, coccinelline), and relationships between these traits. High-diet individuals had greater total precoccinelline levels, and elytra carotenoid concentrations at adulthood which was detectable to a typical avian predator. However, larval diet did not significantly affect adult body mass or size, spot size or coccinelline levels. Elytra carotenoid concentrations correlated positively with total precoccinelline levels in both diet groups and sexes. However, the relationship between elytra carotenoid concentrations and total levels of coccinelline depended on sex: in both diet groups, elytra carotenoids and coccinelline levels were positively correlated in females, but negatively correlated in males. Spot size and coccinelline levels correlated positively in Low-diet individuals, but negatively in High-diet individuals. These results point to physiological linkages between components of aposematism, which are modulated by resource (i.e. food) availability and affect the honesty of signals. Developmental diet, but also sex, influenced the relationships between signals and toxin levels. Ladybirds are sexually size dimorphic, and thus in comparison with males, females may be more susceptible to resource limitation and more likely to be honest signallers. © 2012 the Authors. Functional Ecology © 2012 British Ecological Society.
Abstract.
Blount JD, Rowland HM, Drijfhout FP, Endler JA, Inger R, Sloggett JJ, Hurst GDD, Hodgson DJ, Speed MP (2012). How the ladybird got its spots: Effects of resource limitation on the honesty of aposematic signals. Functional Ecology
Stott I, Hodgson DJ, Townley S (2012). popdemo: an R package for population demography using projection matrix analysis.
METHODS IN ECOLOGY AND EVOLUTION,
3(5), 797-802.
Author URL.
2011
Stott I, Townley S, Hodgson DJ (2011). A framework for studying transient dynamics of population projection matrix models.
Ecol Lett,
14(9), 959-970.
Abstract:
A framework for studying transient dynamics of population projection matrix models.
Empirical models are central to effective conservation and population management, and should be predictive of real-world dynamics. Available modelling methods are diverse, but analysis usually focuses on long-term dynamics that are unable to describe the complicated short-term time series that can arise even from simple models following ecological disturbances or perturbations. Recent interest in such transient dynamics has led to diverse methodologies for their quantification in density-independent, time-invariant population projection matrix (PPM) models, but the fragmented nature of this literature has stifled the widespread analysis of transients. We review the literature on transient analyses of linear PPM models and synthesise a coherent framework. We promote the use of standardised indices, and categorise indices according to their focus on either convergence times or transient population density, and on either transient bounds or case-specific transient dynamics. We use a large database of empirical PPM models to explore relationships between indices of transient dynamics. This analysis promotes the use of population inertia as a simple, versatile and informative predictor of transient population density, but criticises the utility of established indices of convergence times. Our findings should guide further development of analyses of transient population dynamics using PPMs or other empirical modelling techniques.
Abstract.
Author URL.
Pincheira-Donoso D, Fox SF, Scolaro JA, Ibargüengoytía N, Acosta JC, Corbalán V, Medina M, Boretto J, Villavicencio HJ, Hodgson DJ, et al (2011). Body size dimensions in lizard ecological and evolutionary research: Exploring the predictive power of mass estimation equations in two liolaemidae radiations.
Herpetological Journal,
21(1), 35-42.
Abstract:
Body size dimensions in lizard ecological and evolutionary research: Exploring the predictive power of mass estimation equations in two liolaemidae radiations
Body size infuences patterns of variation in several of the most important traits directly linked to fitness. Therefore, the establishment of informative proxies for body size is a critical aim in ecological and evolutionary research. Among lizards, snout-vent length (SVL) is the most widely used proxy for body size. However, since SVL is a linear measure of size, it fails to capture body shape variation. This limitation is largely resolved by the use of body mass, a multidimensional measure of size that is unfortunately rarely considered and reported. To circumvent this restriction, a classic allometric equation (Pough's equation) was proposed to convert SVL into mass. Nevertheless, the predictive power of this equation has been assumed rather than empirically tested for almost three decades. In a recent study on lizard size allometries, additional equations were derived for different groups separately, suggesting that more clade-specifc equations are likely to perform better. Here, we investigate the precision of these allometric equations using two sister lizard genera (Liolaemus and Phymaturus), members of the Liolaemidae radiation, for which SVL and mass have been measured. We found that our equations differ signifcantly from the two more general equations primarily in intercepts, while the more clade-specifc equation derived for Tropiduridae lizards is fully compatible with our equation for Liolaemus and showed only a borderline statistical difference with Phymaturus. Therefore, although more clade-specifc equations may reliably predict body mass, more general equations should be used with caution in lizard ecological and evolutionary research. Previous allometric equations proposed to predict mass from length in other ectotherms should be quantitatively assessed before being employed.
Abstract.
Özden O, Hodgson DJ (2011). Butterflies (Lepidoptera) highlight the ecological value of shrubland and grassland mosaics in Cypriot garrigue ecosystems.
European Journal of Entomology,
108(3), 431-437.
Abstract:
Butterflies (Lepidoptera) highlight the ecological value of shrubland and grassland mosaics in Cypriot garrigue ecosystems
We used butterfly assemblages to evaluate the ecological value of habitat mosaics within garrigue ecosystems in Cyprus. To understand the importance of the local plant communities for Cypriot butterflies, five plots in each of two habitat types (grass-dominated or shrub-dominated) were surveyed weekly for a period of five months in order to assess the abundance, species richness and diversity of butterflies. A total of 810 butterflies of 16 species were recorded. Indices of butterfly diversity, calculated across the whole season, were similar between grassland and shrubland dominated mosaics. However, species richness of all butterflies was consistently higher in grassland dominated mosaics throughout the whole season. The peak abundance of all butterfly species occurred during mid-season (late April - early May), with similar numbers observed in both habitat types. However, a greater abundance was observed during early and late season in grassland patches. The abundance of endemic species (Maniola cypricola, Hipparchia cypriensis, Glaucopsyche paphos) peaked earlier in the season in shrubland patches, but was higher in grassland patches in late season. This difference in seasonal timing of endemic abundance was dominated by the seasonal dynamics of M. cypricola. These results suggest that, while garrigue is characterised by its shrub flora, management to maintain a mosaic of grassland and shrubland could act to maximise the abundance and richness of indicator species groups of conservation importance.
Abstract.
Smee M, Smyth W, Tunmore M, ffrench-Constant R, Hodgson D (2011). Butterflies on the brink: Habitat requirements for declining populations of the marsh fritillary (Euphydryas aurinia) in SW England.
Journal of Insect Conservation,
15(1), 153-163.
Abstract:
Butterflies on the brink: Habitat requirements for declining populations of the marsh fritillary (Euphydryas aurinia) in SW England
1. The marsh fritillary Euphydryas aurinia is one of our most endangered butterflies, and the only to be protected under European legislation as well as British. It persists in fragile subpopulations threatened by habitat fragmentation and degradation. 2. A combination of swaling and cattle grazing are accepted to be best practice for managing wet, unimproved grasslands-the favoured habitat for E. aurinia in Cornwall. These two well-endorsed methods of management were used to increase and improve the quality of habitat for E. aurinia over a 5 years period, 2004-2008, at a stronghold network of habitat patches in mid Cornwall, south-west England. 3. Analyses of adult and larval densities over 5 years in fifty-four transects across nine sites found E. aurinia to favour habitat patches with higher densities of the larval food plant (Devil's-bit scabious Succisa pratensis), higher sward height in autumn, and intermediate optimum levels of stock grazing. 4. Main findings indicated most sites experienced significant declines in numbers. Unfavourable weather in the last 2 years of monitoring was likely to have had a significant impact on the response of individual subpopulations to habitat management though poor recovery rates may also reflect a time-lag in colonisation events after habitat improvement has occurred. 5. Habitat management produced an improvement, albeit an inconsistent improvement in habitat variables across patches-S. pratensis shows a clear recovery at some sites. Autumn sward height increased significantly at one site, and a quadratic relationship between stock grazing and important habitat variables has been found which will aid further improvement over all sites for the long term persistence of E. aurinia. © 2010 Springer Science+Business Media B.V.
Abstract.
Smee M, Smyth W, Tunmore M, Ffrench-Constant R, Hodgson D (2011). Butterflies on the brink: habitat requirements for declining populations of the marsh fritillary (Euphydryas aurinia) in SW England.
J INSECT CONSERV,
15(1-2), 153-163.
Abstract:
Butterflies on the brink: habitat requirements for declining populations of the marsh fritillary (Euphydryas aurinia) in SW England
1. The marsh fritillary Euphydryas aurinia is one of our most endangered butterflies, and the only to be protected under European legislation as well as British. It persists in fragile subpopulations threatened by habitat fragmentation and degradation. 2. A combination of swaling and cattle grazing are accepted to be best practice for managing wet, unimproved grasslands-the favoured habitat for E. aurinia in Cornwall. These two well-endorsed methods of management were used to increase and improve the quality of habitat for E. aurinia over a 5 years period, 2004-2008, at a stronghold network of habitat patches in mid Cornwall, south-west England. 3. Analyses of adult and larval densities over 5 years in fifty-four transects across nine sites found E. aurinia to favour habitat patches with higher densities of the larval food plant (Devil's-bit scabious Succisa pratensis), higher sward height in autumn, and intermediate optimum levels of stock grazing. 4. Main findings indicated most sites experienced significant declines in numbers. Unfavourable weather in the last 2 years of monitoring was likely to have had a significant impact on the response of individual subpopulations to habitat management though poor recovery rates may also reflect a time-lag in colonisation events after habitat improvement has occurred. 5. Habitat management produced an improvement, albeit an inconsistent improvement in habitat variables across patches-S. pratensis shows a clear recovery at some sites. Autumn sward height increased significantly at one site, and a quadratic relationship between stock grazing and important habitat variables has been found which will aid further improvement over all sites for the long term persistence of E. aurinia.
Abstract.
Davies TE, Wilson S, Hazarika N, Chakrabarty J, Das D, Hodgson DJ, Zimmermann A (2011). Effectiveness of intervention methods against crop-raiding elephants.
Conservation Letters,
4(5), 346-354.
Abstract:
Effectiveness of intervention methods against crop-raiding elephants
The raiding of crops by elephants is one of the major components of human-elephant conflict, causing loss of livelihood and retaliation against elephants. To mitigate this conflict, various intervention methods are in use by farmers across Africa and Asia; yet there have been few rigorous assessments of their effectiveness. We provide an assessment of the efficacy of interventions in use by communities in Assam from a 3-year survey dataset using Generalized Linear Mixed Modeling. We found spotlights, chili fences, and electric fences to be highly effective at preventing crop damage by elephants when used in isolation, but when used in combination with noise their efficacy was compromised. Our study highlights the importance of evaluating intervention methods to determine their effectiveness. We propose the use of fences and spotlights be promoted in Assam, in conjunction with long-term habitat protection and restoration strategies. ©2011 Wiley Periodicals, Inc.
Abstract.
Harrison XA, Bearhop S, Inger R, Colhoun K, Gudmundsson GA, Hodgson D, McElwaine G, Tregenza T (2011). Heterozygosity-fitness correlations in a migratory bird: an analysis of inbreeding and single-locus effects.
MOLECULAR ECOLOGY,
20(22), 4786-4795.
Author URL.
Harrison XA, Bearhop S, Inger R, Colhoun K, Gudmundsson GA, Hodgson D, McElwaine G, Tregenza T (2011). Heterozygosity-fitness correlations in a migratory bird: an analysis of inbreeding and single-locus effects.
Molecular ecology,
20(22), 4786-4795.
Abstract:
Heterozygosity-fitness correlations in a migratory bird: an analysis of inbreeding and single-locus effects.
Studies in a multitude of taxa have described a correlation between heterozygosity and fitness and usually conclude that this is evidence for inbreeding depression. Here, we have used multilocus heterozygosity (MLH) estimates from 15 microsatellite markers to show evidence of heterozygosity-fitness correlations (HFCs) in a long-distance migratory bird, the light-bellied Brent goose. We found significant, positive heterozygosity-heterozygosity correlations between random subsets of the markers we employed, and no evidence that a model containing all loci as individual predictors in a multiple regression explained significantly more variation than a model with MLH as a single predictor. Collectively, these results lend support to the hypothesis that the HFCs we have observed are a function of inbreeding depression. However, we do find that fitness correlations are only detectable in years where population-level productivity is high enough for the reproductive asymmetry between high and low heterozygosity individuals to become apparent. We suggest that lack of evidence of heterozygosity-fitness correlations in animal systems may be because heterozygosity is a poor proxy measure of inbreeding, especially when employing low numbers of markers, but alternatively because the asymmetries between individuals of different heterozygosities may only be apparent when environmental effects on fitness are less pronounced. © 2011 Blackwell Publishing Ltd.
Abstract.
Harris CA, Hamilton PB, Runnalls TJ, Vinciotti V, Henshaw A, Hodgson D, Coe TS, Jobling S, Tyler CR, Sumpter JP, et al (2011). The consequences of feminization in breeding groups of wild fish.
Environ Health Perspect,
119(3), 306-311.
Abstract:
The consequences of feminization in breeding groups of wild fish.
BACKGROUND: the feminization of nature by endocrine-disrupting chemicals (EDCs) is a key environmental issue affecting both terrestrial and aquatic wildlife. A crucial and as yet unanswered question is whether EDCs have adverse impacts on the sustainability of wildlife populations. There is widespread concern that intersex fish are reproductively compromised, with potential population-level consequences. However, to date, only in vitro sperm quality data are available in support of this hypothesis. OBJECTIVE: the aim of this study was to examine whether wild endocrine-disrupted fish can compete successfully in a realistic breeding scenario. METHODS: in two competitive breeding experiments using wild roach (Rutilus rutilus), we used DNA microsatellites to assign parentage and thus determine reproductive success of the adults. RESULTS: in both studies, the majority of intersex fish were able to breed, albeit with varying degrees of success. In the first study, where most intersex fish were only mildly feminized, body length was the only factor correlated with reproductive success. In the second study, which included a higher number of more severely intersex fish, reproductive performance was negatively correlated with severity of intersex. The intersex condition reduced reproductive performance by up to 76% for the most feminized individuals in this study, demonstrating a significant adverse effect of intersex on reproductive performance. CONCLUSION: Feminization of male fish is likely to be an important determinant of reproductive performance in rivers where there is a high prevalence of moderately to severely feminized males.
Abstract.
Author URL.
2010
Stott I, Franco M, Carslake D, Townley S, Hodgson D (2010). Boom or bust? a comparative analysis of transient population dynamics in plants.
Journal of Ecology,
98(2), 302-311.
Abstract:
Boom or bust? a comparative analysis of transient population dynamics in plants
Population dynamics often defy predictions based on empirical models, and explanations for noisy dynamics have ranged from deterministic chaos to environmental stochasticity. Transient (short-term) dynamics following disturbance or perturbation have recently gained empirical attention from researchers as further possible effectors of complicated dynamics. Previously published methods of transient analysis have tended to require knowledge of initial population structure. However, this has been overcome by the recent development of the parametric Kreiss bound (which describes how large a population must become before reaching its maximum possible transient amplification following a disturbance) and the extension of this and other transient indices to simultaneously describe both amplified and attenuated transient dynamics. We apply the Kreiss bound and other transient indices to a data base of matrix models from 108 plant species, in an attempt to detect ecological and mathematical patterns in the transient dynamical properties of plant populations. We describe how life history influences the transient dynamics of plant populations: species at opposite ends of the scale of ecological succession have the highest potential for transient amplification and attenuation, whereas species with intermediate life history complexity have the lowest potential. We find ecological relationships between transients and asymptotic dynamics: faster-growing populations tend to have greater potential magnitudes of transient amplification and attenuation, which could suggest that short- and long-term dynamics are similarly influenced by demographic parameters or vital rates. We describe a strong dependence of transient amplification and attenuation on matrix dimension: perhaps signifying a potentially worrying artefact of basic model parameterization. Synthesis. Transient indices describe how big or how small plant populations can get, en route to long-term stable rates of increase or decline. The patterns we found in the potential for transient dynamics, across many species of plants, suggest a combination of ecological and modelling strategy influences. This better understanding of transients should guide the formulation of management and conservation strategies for all plant populations that suffer disturbances away from stable equilibria. © 2010 the Authors. Journal compilation © 2010 British Ecological Society.
Abstract.
Smee M, Smyth W, Tunmore M, ffrench-Constant R, Hodgson D (2010). Butterflies on the brink: habitat requirements for declining populations of the marsh fritillary (Euphydryas aurinia) in SW England. In (Ed) Lepidoptera Conservation in a Changing World, Springer Netherlands, 189-199.
Inger R, Harrison XA, Ruxton GD, Newton J, Colhoun K, Gudmundsson GA, McElwaine G, Pickford M, Hodgson D, Bearhop S, et al (2010). Carry-Over Effects Reveal Reproductive Costs in a Long Distance Migrant. Journal of Animal Ecology, 79, 974-982.
Harrison XA, Tregenza T, Inger R, Colhoun K, Dawson DA, Gudmundsson GA, Hodgson DJ, Horsburgh GJ, McElwaine G, Bearhop S, et al (2010). Cultural Inheritance Drives Site Fidelity and Migratory Connectivity in a Long Distance Migrant. Molecular Ecology, 19(24), 5484-5496.
Coe TS, Söffker MK, Filby AL, Hodgson D, Tyler CR (2010). Impacts of early life exposure to estrogen on subsequent breeding behavior and reproductive success in zebrafish.
Environ Sci Technol,
44(16), 6481-6487.
Abstract:
Impacts of early life exposure to estrogen on subsequent breeding behavior and reproductive success in zebrafish.
Impacts of exposure to environmental estrogens on reproductive development are well documented, but recently wider concern has been raised due to evidence that such exposures can disrupt normal patterns of reproductive behavior, dominance, and parentage, with potential population level implications. It is fundamental therefore to understand any such effects for effective risk assessment. This study investigated the impact of a transient exposure to ethinylestradiol (EE(2)) during early life (from 20-60 days post fertilization), including at a dosing level within the environmental range, on the subsequent reproductive behavior and success in both male and female zebrafish (Danio rerio) in competitive breeding scenarios. There were no obvious effects of the early life EE(2) exposures on the subsequent gonadal phenotypes in either mature males or females. In fact, reproductive success in males exposed to 2.76 ng EE(2)/L was increased in competitive spawning scenarios. In contrast, exposure of females to EE(2) (9.86 ng/L) during early life reduced their subsequent reproductive success in competitive spawning scenarios. Mate choice experiments suggested this was a consequence of the females' diminished courting behavior toward males, rather than any male preference for unexposed females. Reproductive capability of females is generally considered a key determinant in population demographics and dynamics, and therefore the effect of exposure to EE(2) on female reproductive success may have significant implications for exposed fish populations.
Abstract.
Author URL.
Stott I, Townley S, Carslake D, Hodgson DJ (2010). On reducibility and ergodicity of population projection matrix models. Methods in Ecology and Evolution, 1, 242-252.
Newton E, Bullock JM, Hodgson D (2010). Temporal consistency in herbivore responses to glucosinolate polymorphism in populations of wild cabbage (Brassica oleracea).
Oecologia,
164(3), 689-699.
Abstract:
Temporal consistency in herbivore responses to glucosinolate polymorphism in populations of wild cabbage (Brassica oleracea).
Natural populations of wild cabbage (Brassica oleracea) show significant qualitative diversity in heritable aliphatic glucosinolates, a class of secondary metabolites involved in defence against herbivore attack. One candidate mechanism for the maintenance of this diversity is that differential responses among herbivore species result in a net fitness balance across plant chemotypes. Such top-down differential selection would be promoted by consistent responses of herbivores to glucosinolates, temporal variation in herbivore abundance, and fitness impacts of herbivore attack on plants varying in glucosinolate profile. A 1-year survey across 12 wild cabbage populations demonstrated differential responses of herbivores to glucosinolates. We extended this survey to investigate the temporal consistency of these responses, and the extent of variation in abundance of key herbivores. Within plant populations, the aphid Brevicoryne brassicae consistently preferred plants producing the glucosinolate progoitrin. Among populations, increasing frequencies of sinigrin production correlated positively with herbivory by whitefly Aleyrodes proletella and negatively with herbivory by snails. Two Pieris butterfly species showed no consistent response to glucosinolates among years. Rates of herbivory varied significantly among years within populations, but the frequency of herbivory at the population scale varied only for B. brassicae. B. brassicae emerges as a strong candidate herbivore to impose differential selection on glucosinolates, as it satisfies the key assumptions of consistent preferences and heterogeneity in abundance. We show that variation in plant secondary metabolites structures the local herbivore community and that, for some key species, this structuring is consistent over time. We discuss the implications of these patterns for the maintenance of diversity in plant defence chemistry.
Abstract.
Author URL.
2009
Pincheira-Donoso D, Hodgson DJ, Stipala J, Tregenza T (2009). A phylogenetic analysis of sex-specific evolution of ecological morphology in Liolaemus lizards.
Ecological Research,
24(6), 1223-1231.
Abstract:
A phylogenetic analysis of sex-specific evolution of ecological morphology in Liolaemus lizards
Adaptive radiation theory predicts that phenotypic traits involved in ecological performance evolve in different directions in populations subjected to divergent natural selection, resulting in the evolution of ecological diversity. This idea has largely been supported through comparative studies exploring relationships between ecological preferences and quantitative traits among different species. However, intersexual perspectives are often ignored. Indeed, although it is well established that intersexual competition and sex-specific parental and reproductive roles may often subject sex-linked phenotypes to antagonistic selection effects, most ecomorphological research has explored adaptive evolution on a single sex, or on means obtained from both sexes together. The few studies taking sexual differences into account reveal the occurrence of sex-specific ecomorphs in some clades of lizards, and conclude that the independent contribution of the sexes to the morphological diversity produced by adaptive radiation can be substantial. Here, we investigate whether microhabitat use results in the evolution of sex-specific ecomorphs across 44 Liolaemus lizard species. We found that microhabitat structure does not predict variation in body size and shape in either of the sexes. Yet, we found that males and females tend to occupy significantly different positions in multivariate morphological spaces, indicating that treating males and females as ecologically and phenotypically equivalent units may lead to incomplete or mistaken estimations of the diversity produced by adaptive evolution. © the Ecological Society of Japan 2009.
Abstract.
Newton E, Bullock JM, Hodgson D (2009). Bottom-up effects of glucosinolate variation on aphid colony dynamics in wild cabbage populations.
Ecological Entomology,
34(5), 614-623.
Abstract:
Bottom-up effects of glucosinolate variation on aphid colony dynamics in wild cabbage populations
1. There is an ongoing debate about the relative importance of top-down and bottom-up regulation of herbivore dynamics in the wild. Secondary metabolites, produced by plants, have negative effects on survival and growth of some herbivore species, causing bottom-up regulation of population dynamics. Herbivore natural enemies may use plant secondary metabolites as cues to find their prey, but their survival and reproduction can also be influenced by the upward cascade of secondary metabolites through the food web. Thus plant chemistry might also affect herbivore populations by mediating top-down regulation. 2. We investigated the influence of heritable variation in aliphatic glucosinolates, a class of secondary metabolites produced by Brassica plants, on the relative importance of top-down and bottom-up regulation of Brevicoryne brassicae (mealy cabbage aphid) colonies in natural Brassica oleracea (wild cabbage) populations. We manipulated natural enemy pressure on plants differing in their glucosinolate profiles, and monitored aphid colony growth and disperser production. 3. Aphid colony sizes were significantly smaller on plants producing sinigrin, compared with plants producing alternative aliphatic glucosinolates. Aphid natural enemy numbers correlated with aphid colony size, but there was no additional effect of the plants' chemical phenotype on natural enemy abundance. Furthermore, experimental reduction of natural enemy pressure had no effect on aphid colony size or production of winged dispersers. 4. Our results provide evidence for glucosinolate-mediated, bottom-up regulation of mealy cabbage aphid colonies in natural populations, but we found no indication of top-down regulation. We emphasise that more studies of these processes should focus on tritrophic interactions in the wild. © 2009 the Royal Entomological Society.
Abstract.
Coe TS, Hamilton PB, Griffiths AM, Hodgson DJ, Wahab MA, Tyler CR (2009). Genetic variation in strains of zebrafish (Danio rerio) and the implications for ecotoxicology studies.
Ecotoxicology,
18(1), 144-150.
Abstract:
Genetic variation in strains of zebrafish (Danio rerio) and the implications for ecotoxicology studies.
There is substantial evidence that genetic variation, at both the level of the individual and population, has a significant effect on behaviour, fitness and response to toxicants. Using DNA microsatellites, we examined the genetic variation in samples of several commonly used laboratory strains of zebrafish, Danio rerio, a model species in toxicological studies. We compared the genetic variation to that found in a sample of wild fish from Bangladesh. Our findings show that the wild fish were significantly more variable than the laboratory strains for several measures of genetic variability, including allelic richness and expected heterozygosity. This lack of variation should be given due consideration for any study which attempts to extrapolate the results of ecotoxicological laboratory tests to wild populations.
Abstract.
Author URL.
Newton EL, Bullock JM, Hodgson DJ (2009). Glucosinolate polymorphism in wild cabbage (Brassica oleracea) influences the structure of herbivore communities.
Oecologia,
160(1), 63-76.
Abstract:
Glucosinolate polymorphism in wild cabbage (Brassica oleracea) influences the structure of herbivore communities.
Natural plant populations often show substantial heritable variation in chemical structure of secondary metabolites. Despite a great deal of evidence from laboratory studies that these chemicals influence herbivore behaviour and life history, there exists little evidence for the structuring of natural herbivore communities according to plant chemical profiles. Brassica oleracea (Brassicaceae) produces aliphatic glucosinolates, which break down into toxins when leaf tissue is damaged. Structural diversity in these glucosinolates is heritable, and varies considerably at two ecological scales in the UK: both within and between populations. We surveyed herbivore attack on plants producing different glucosinolates, using 12 natural B. oleracea populations. In contrast to the results of previous studies in this system, which suffered low statistical power, we found significant differential responses of herbivore species to heritable glucosinolates, both within and between plant populations. We found significant correlations between herbivore infestation rates and the presence or absence of two heritable glucosinolates: sinigrin and progoitrin. There was variation between herbivore species in the direction of response, the ecological scale at which responses were identified, and the correlations for some herbivore species changed at different times of the year. We conclude that variation in plant secondary metabolites can structure the community of herbivores that attack them, and propose that herbivore-mediated differential selection deserves further investigation as a mechanism maintaining the observed diversity of glucosinolates in wild Brassica.
Abstract.
Author URL.
Benmayor R, Hodgson DJ, Perron GG, Buckling A (2009). Host mixing and disease emergence.
Curr Biol,
19(9), 764-767.
Abstract:
Host mixing and disease emergence.
Recent cases of emergent diseases have renewed interest in the evolutionary and ecological mechanisms that promote parasite adaptation to novel hosts [1-6]. Crucial to adaptation is the degree of mixing of original, susceptible hosts, and novel hosts. An increase in the frequency of the original host has two opposing effects on adaptation: an increase in the supply of mutant pathogens with improved performance on the novel host [7-9]; and reduced selection to infect novel hosts, caused by fitness costs commonly observed to be associated with host switching [10-17]. The probability of disease emergence will therefore peak at intermediate frequencies of the original host. We tested these predictions by following the evolution of a virus grown under a range of different frequencies of susceptible (original) and resistant (novel) host bacteria. Viruses that evolved to infect resistant hosts were only detected when susceptible hosts were at frequencies between 0.1% and 1%. Subsequent experiments supported the predictions that there was reduced selection and mutation supply at higher and lower frequencies, respectively. These results suggest that adaptation to novel hosts can occur only under very specific ecological conditions, and that small changes in contact rates between host species might help to mitigate disease emergence.
Abstract.
Author URL.
Inger R, Attrill MJ, Bearhop S, Broderick AC, James Grecian W, Hodgson DJ, Mills C, Sheehan E, Votier SC, Witt MJ, et al (2009). Marine renewable energy: Potential benefits to biodiversity? an urgent call for research.
Journal of Applied Ecology,
46(6), 1145-1153.
Abstract:
Marine renewable energy: Potential benefits to biodiversity? an urgent call for research
The evidence for anthropogenically induced climate change is overwhelming with the production of greenhouse gases from burning fossil fuels being a key driver. In response, many governments have initiated programmes of energy production from renewable sources. 2. The marine environment presents a relatively untapped energy source and offshore installations are likely to produce a significant proportion of future energy production. Wind power is the most advanced, with development of wave and tidal energy conversion devices expected to increase worldwide in the near future. 3. Concerns over the potential impacts on biodiversity of marine renewable energy installations (MREI) include: habitat loss, collision risks, noise and electromagnetic fields. These factors have been posited as having potentially important negative environmental impacts. 4. Conversely, we suggest that if appropriately managed and designed, MREI may increase local biodiversity and potentially benefit the wider marine environment. Installations have the capacity to act as both artificial reefs and fish aggregation devices, which have been used previously to facilitate restoration of damaged ecosystems, and de facto marine-protected areas, which have proven successful in enhancing both biodiversity and fisheries. 5. The deployment of MREI has the potential to cause conflict among interest groups including energy companies, the fishing sector and environmental groups. Conflicts should be minimized by integrating key stakeholders into the design, siting, construction and operational phases of the installations, and by providing clear evidence of their potential environmental benefits. 6. Synthesis and applications. MREI have the potential to be both detrimental and beneficial to the environment but the evidence base remains limited. To allow for full biodiversity impacts to be assessed, there exists an urgent need for additional multi and inter-disciplinary research in this area ranging from engineering to policy. Whilst there are a number of factors to be considered, one of the key decisions facing current policy makers is where installations should be sited, and, dependent upon site, whether they should be designed to either minimize negative environmental impacts or as facilitators of ecosystem restoration. © 2009 British Ecological Society.
Abstract.
Coe TS, Hamilton PB, Hodgson D, Paull GC, Tyler CR (2009). Parentage outcomes in response to estrogen exposure are modified by social grouping in zebrafish.
Environ Sci Technol,
43(21), 8400-8405.
Abstract:
Parentage outcomes in response to estrogen exposure are modified by social grouping in zebrafish.
Evidence has recently emerged that endocrine-disrupting chemicals (EDCs) can affect various behaviors, including dominance and aggression in social groups, including fish. This study investigated the effect of short-term exposure of male adult zebrafish to 17alpha-ethinylestradiol (EE(2)) on subsequent reproductive output and parentage in colonies with differing numbers of competing males. It was predicted that impacts of EDCs might differ in social groups of fish of differing size because of the greater costs of maintaining dominance hierarchies in large groups. Adult male zebrafish were exposed for 14 days to clean water, 2 ng/L EE(2) or 10 ng/L via the water, prior to placement into colonies in clean water with unexposed females. Exposure to EE(2) at the concentrations adopted prior to the breeding trials did not significantly affect subsequent colony reproductive output. The reproductive success of the most reproductively successful (MRS) male within colonies containing two males (relative to controls) was also unaffected. There was, however, a significant impact of previous EE(2) exposure in tanks containing four males, resulting in a reduction in paternity for the most successful male. Hence, nonlethal behavioral impacts of even short-term exposure to EDCs can have significant impacts on social dominance hierarchies and population genetic diversity.
Abstract.
Author URL.
Carslake D, Townley S, Hodgson DJ (2009). Patterns and rules for sensitivity and elasticity in population projection matrices.
Ecology,
90(11), 3258-3267.
Abstract:
Patterns and rules for sensitivity and elasticity in population projection matrices.
Sensitivity and elasticity analysis of population projection matrices (PPMs) are established tools in the analysis of structured populations, allowing comparison of the contributions made by different demographic rates to population growth. In some commonly used structures of PPM, however, there are mathematically inevitable patterns in the relative sensitivity and elasticity of certain demographic rates. We take a simulation approach to investigate these mathematical constraints for a range of PPM models. Our results challenge some previously proposed constraints on sensitivity and elasticity. We also identify constraints beyond those that have already been proven mathematically and promote them as candidates for future mathematical proof. A general theme among these rules is that changes to the demographic rates of older or larger individuals have less impact on population growth than do equivalent changes among younger or smaller individuals. However, the validity of these rules in each case depends on the choice between sensitivity and elasticity, the growth rate of the population, and the PPM structure used. If the structured population conforms perfectly to the assumptions of the PPM used to model it, the rules we describe represent biological reality, allowing us to prioritize management strategies in the absence of detailed demographic data. Conversely, if the model is a poor fit to the population (specifically, if demographic rates within stages are heterogeneous), such analyses could lead to inappropriate management prescriptions. Our results emphasize the importance of choosing a structured population model that fits the demographics of the population.
Abstract.
Author URL.
Carslake D, Townley S, Hodgson DJ (2009). Predicting the impact of stage-specific harvesting on population dynamics.
J Anim Ecol,
78(5), 1076-1085.
Abstract:
Predicting the impact of stage-specific harvesting on population dynamics.
1. Perturbation analyses of population projection matrices predict the response of a population's growth rate to changes in lifestage-specific vital rates. Such predictions have been widely used in population management but their reliability remains hotly debated. 2. We grew replicate populations of the water flea Daphnia magna in controlled, density-independent conditions and subjected treatment populations to harvesting of the largest lifestage. We predicted the growth rate of treatment populations using sensitivity analysis (a linear approximation), and transfer function analysis (TFA; which captures nonlinear responses) applied to projection matrix models parameterized from the control populations. 3. When perturbation analyses considered only the direct effect of harvesting on adult survival, the growth rate of harvested populations (averaging 0.051) was significantly overestimated (average of 0.112) by TFA and non-significantly underestimated (average of 0.012) by sensitivity. 4. When the indirect effects of harvesting on other vital rates were accounted for in a structured perturbation, TFA gave accurate predictions (average growth rate of 0.068), while sensitivity gave significant underestimates (average of -0.043). 5. Our results demonstrate two crucial sources of error that may influence predictions of the impacts of demographic perturbations on population dynamics. First, impacts of stage-specific harvesting are inherently nonlinear, hence predictions based on sensitivity must be treated with caution. Second, stage-specific perturbations can change non-target demographic rates, even in the absence of adaptation. 6. Population managers should consider both nonlinear and indirect effects of perturbations when designing management interventions. We encourage the development of methods to assess the robustness of predictions to unforeseen perturbation structures and indirect harvesting impacts.
Abstract.
Author URL.
Hosken DJ, Martin OY, Wigby S, Chapman T, Hodgson DJ (2009). Sexual conflict and reproductive isolation in flies.
Biol Lett,
5(5), 697-699.
Abstract:
Sexual conflict and reproductive isolation in flies.
Sexual conflict is predicted to generate more rapid reproductive isolation between larger populations. While there is some empirical support for this, the data are inconsistent and, additionally, there has been criticism of some of the evidence. Here we reanalyse two experimental-evolution datasets using an isolation index widely applied in the speciation literature. We find evidence for reproductive isolation through sexual conflict in Sepsis cynipsea, but not in Drosophila melanogaster, and this occurred to a greater degree in larger populations, which is consistent with previous findings.
Abstract.
Author URL.
Sebire M, Scott AP, Tyler CR, Cresswell J, Hodgson DJ, Morris S, Sanders MB, Stebbing PD, Katsiadaki I (2009). The organophosphorous pesticide, fenitrothion, acts as an anti-androgen and alters reproductive behavior of the male three-spined stickleback, Gasterosteus aculeatus.
Ecotoxicology,
18(1), 122-133.
Abstract:
The organophosphorous pesticide, fenitrothion, acts as an anti-androgen and alters reproductive behavior of the male three-spined stickleback, Gasterosteus aculeatus.
Fenitrothion (FN) is a widely used organophosphorous pesticide that has structural similarities with the clinical anti-androgen flutamide. The potential for FN to act as an anti-androgen (at exposures of 1, 50, and 200 microg FN/l over a 26-day period) was assessed in male three-spined sticklebacks, Gasterosteus aculeatus, by measuring kidney spiggin concentration, nest-building, and courtship behavior. Spiggin is the glue protein that male sticklebacks use to build their nests and is directly controlled by androgens. FN exposure significantly reduced spiggin production as well as nest-building activity. It also adversely affected courtship--especially the 'zigzag dance' and biting behavior of the males. FN thus appears to have anti-androgenic effects on both the physiology and behavior of the male stickleback.
Abstract.
Author URL.
Rainey PB, Brockhurst M, Buckling A, Hodgson DJ, Kassen R (2009). The use of model Pseudomonas fluorescens populations to study the causes and consequences of microbial diversity. In (Ed) Biological Diversity and Function in Soils, Cambridge University Press (CUP), 83-99.
2008
Coe TS, Hamilton PB, Hodgson D, Paull GC, Stevens JR, Sumner K, Tyler CR (2008). An environmental estrogen alters reproductive hierarchies, disrupting sexual selection in group-spawning fish.
ENVIRONMENTAL SCIENCE & TECHNOLOGY,
42(13), 5020-5025.
Author URL.
Ozden O, Ciesla WM, Fuller WJ, Hodgson DJ (2008). Butterfly diversity in Mediterranean islands and in Pentadaktylos Pinus brutia forests of Cyprus. Biodiversity and Conservation, 17, 2821-2832.
Scott DM, Rabineau J, Wilson RW, Hodgson DJ, Brown JA (2008). Can pikeperch colonise new freshwater systems via estuaries? Evidence from behavioural salinity tests.
Marine and Freshwater Research,
59(8), 694-702.
Abstract:
Can pikeperch colonise new freshwater systems via estuaries? Evidence from behavioural salinity tests
Pikeperch (Sander lucioperca) are non-native in the United Kingdom. It is important to understand how environmental factors, such as salinity, influence the behaviour and activity of introduced fish species to identify their dispersal potential. Previous studies have shown that pikeperch, traditionally recognised as a freshwater fish, can tolerate brackish waters and demonstrate physiological acclimation. However, their behavioural responses to brackish waters are unknown. The aim of the present study was therefore to investigate the activity and swimming behaviour of pikeperch obtained from freshwater canals in southern England. In the laboratory, fish were exposed to a 12-h simulated tidal cycle and a 12-day stepped salinity challenge where salinity was increased by 4 every 2 days, up to a salinity of 20. In both regimes, fish showed increased swimming activity in response to increasing salinity, which may represent an avoidance response. The most dramatic changes, including vertical movements, occurred at salinities above ∼16. At these higher salinities, head shaking and coughing behaviours were also observed, suggesting significant stress and respiratory impairment. However, during the simulated tidal cycle, normal behaviour was rapidly restored once salinity was reduced. The results of this study may have implications in understanding the dispersal of non-native fish in the wild. © CSIRO 2008.
Abstract.
Pincheira-Donoso D, Hodgson DJ, Tregenza T (2008). Comparative evidence for strong phylogenetic inertia in precloacal signalling glands in a species-rich lizard clade. Evolutionary Ecology Research, 10, 11-28.
Townley S, Hodgson DJ (2008). Erratum et addendum: Transient amplification and attenuation in stage-structured population dynamics.
Journal of Applied Ecology,
45(6), 1836-1839.
Abstract:
Erratum et addendum: Transient amplification and attenuation in stage-structured population dynamics
1. Not all members of natural populations contribute equally to population growth or decline. Populations that are disturbed away from stable stage structure will amplify (i.e. get bigger than expected) and/or attenuate (i.e. get smaller than expected) in the short term. 2. We provide mathematical bounds for the magnitude of this amplification and attenuation, both in terms of absolute population change and population change relative to the long-term rate of population increase. 3. Our results correct an important error in an earlier analysis of transient population amplification, and provide new transient bounds for the analysis of population attenuation. 4. Synthesis and applications. Bounds on transient amplification and attenuation help population managers to gauge 'worst case' and 'best case' scenarios for the response of stage-structured populations to disturbance and management strategies. Such bounds help to create an envelope of possible future population scenarios around the mean, long-term predictions made by eigenvalues and eigenvectors of projection matrix models. Transient amplification, caused by stage structures biased towards reactive life stages, may be exploited by conservation managers wishing to boost population densities in the short term and may be avoided in pest species by stage-specific control strategies. Similarly, transient attenuation should be avoided by conservation managers and exploited by pest managers. © 2008 the Authors.
Abstract.
Carslake DJ, Townley S, Hodgson DJ (2008). Nonlinearity in eigenvalue-perturbation curves of simulated population projection matrices. Theoretical Population Biology, 73, 498-505.
McCarthy D, Townley S, Hodgson D (2008). On second order sensitivity for stage-based population projection matrix models. Theoretical Population Biology, 74, 68-73.
Townley S, Hodgson DJ (2008). Predicting transient amplification in perturbed ecological systems (vol 44, pg 1243, 2007).
JOURNAL OF APPLIED ECOLOGY,
45(6), 1836-1839.
Author URL.
Price TAR, Hodgson DJ, Lewis Z, Hurst GDD, Wedell N (2008). Selfish genetic elements promote polyandry in a fly.
Science,
322(5905), 1241-1243.
Abstract:
Selfish genetic elements promote polyandry in a fly.
It is unknown why females mate with multiple males when mating is frequently costly and a single copulation often provides enough sperm to fertilize all a female's eggs. One possibility is that remating increases the fitness of offspring, because fertilization success is biased toward the sperm of high-fitness males. We show that female Drosophila pseudoobscura evolved increased remating rates when exposed to the risk of mating with males carrying a deleterious sex ratio-distorting gene that also reduces sperm competitive ability. Because selfish genetic elements that reduce sperm competitive ability are generally associated with low genetic fitness, they may represent a common driver of the evolution of polyandry.
Abstract.
Author URL.
Pincheira-Donoso D, Hodgson DJ. Tregenza T (2008). The evolution of body size under environmental gradients in ectotherms: why should Bergmann's rule apply to lizards?. BMC Evolutionary Biology, 8
Benmayor R, Buckling A, Bonsall MB, Brockhurst MA, Hodgson DJ (2008). The interactive effects of parasitesf disturbance, and productivity on experimental adaptive radiations.
EVOLUTION,
62(2), 467-477.
Author URL.
Maclean MM, Carslake DJ, Evans MR, Townley S, Hodgson DJ (2008). The usefulness of sensitivity analysis for predicting the effects of cat predation on the population dynamics of their avian prey.
IBIS,
150, 100-113.
Author URL.
2007
Tregenza, T. Hodgson, D.J. (2007). Body size evolution in South American Liolaemus lizards of the boulengeri clade: a contrasting reassessment. Journal of Evolutionary Biology, 20, 2067-2071.
Hitchman RB, Hodgson DJ, King LA, Hails RS, Cory JS, Possee RD (2007). Host mediated selection of pathogen genotypes as a mechanism for the maintenance of baculovirus diversity in the field.
JOURNAL OF INVERTEBRATE PATHOLOGY,
94(3), 153-162.
Author URL.
Brockhurst MA, Colegrave N, Hodgson DJ, Buckling A (2007). Niche Occupation Limits Adaptive Radiation in Experimental Microcosms.
PLOS ONE,
2(2).
Author URL.
Hodgson DJ, Carslake DJ, Kellie-Smith O, Townley S (2007). Predicting transient amplification in disturbed natural systems. Journal of Applied Ecology, 44(6), 1243-1251.
Hodgson, D.J. (2007). Short-term rates of parasite evolution predict the evolution of host diversity. Journal of Evolutionary Biology, 20, 1682-1688.
2006
Hodgson D, Townley S, McCarthy D (2006). Robustness: Predicting the effects of life history perturbations on stage-structured population dynamics.
THEORETICAL POPULATION BIOLOGY,
70(2), 214-224.
Author URL.
Hodgson, DJ, Hosken, D.J. (2006). Sperm competition promotes the exploitation of rival ejaculates. Journal of Theoretical Biology, 243, 230-234.
2004
Hitchman, R.B. Vanbergen, A.J. (2004). Host ecology determines the relative fitness of virus genotypes in mixed-genotype nucleopolyhedrovirus infections. Journal of Evolutionary Biology, 17(5), 1018-1025.
Hodgson DJ, Townley S (2004). Linking management changes to population dynamic responses: the transfer function of a projection matrix perturbation. Journal of Applied Ecology, 41(6), 1155-1161.
2003
Vanbergen AJ, Hodgson DJ, Thurlow M, Hartley SE, Watt AD (2003). Food-plant effects on larval performance do not translate into differences in fitness between populations of Panolis flammea (Lepidoptera: Noctuidae).
Bull Entomol Res,
93(6), 553-559.
Abstract:
Food-plant effects on larval performance do not translate into differences in fitness between populations of Panolis flammea (Lepidoptera: Noctuidae).
In the UK, Panolis flammea (Denis & Schiffermüller) is a pest of monocultures of non-native lodgepole pine Pinus contorta Douglas, but not of the indigenous host Scots pine P. sylvestrisL. This difference in population dynamics may be due to the adaptation of P. flammea populations to the phenology, chemical composition and natural enemy complement of lodgepole pine. To ascertain if there was local adaptation of P. flammea populations to lodgepole pine, this study tested for improved performance of both larvae and adults on the host plant species from which they were sourced, compared with their performance on the alternative host plant species. No difference was found in the relative mean performance of populations sourced from Scots pine or lodgepole pine plantations, when fed on Scots or lodgepole pine foliage. Larvae grew faster on Scots pine but this difference did not translate into differences in pupal weight, female body weight or fecundity. Indeed, those insects that had fed on lodgepole pine had a longer lifespan than those that had fed on Scots pine, which, if translated into greater probability of mating or higher fecundity, could contribute to the observed outbreak dynamics in the field. The prediction that the observed outbreak dynamics of P. flammea can be explained by the existence of populations locally adapted to lodgepole pine was not supported. These results cast doubt on the use of larval growth parameters as surrogates of fitness in Lepidoptera.
Abstract.
Author URL.
2002
Hodgson, D.J. (2002). An experimental manipulation of the growth and dispersal strategy of a parasitic infection using monoclonal aphid colonies. Evolutionary Ecology Research, 4, 133-145.
Hodgson DJ, Vanbergen AJ, Hartley SE, Hails RS, Cory JS (2002). Differential selection of baculovirus genotypes mediated by different species of host food plant. Ecology Letters, 5(4), 512-518.
Hodgson DJ, Rainey PB, Buckling A (2002). Mechanisms linking diversity, productivity and invasibility in experimental bacterial communities.
PROCEEDINGS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES,
269(1506), 2277-2283.
Author URL.
Hodgson DJ, Hitchman RB, Vanbergen AJ, Hails RS, Hartley SM, Possee RD, Watt AD, Cory JS (2002). The existence and persistence of genotypic variation in nucleopolyhedrovirus populations. In Berenger J, Hails RS, Godfray HCJ (Eds.) Ecological Dynamics and Genes.
2001
Hodgson DJ, Vanbergen AJ, Watt AD, Hails RS, Cory JS (2001). Phenotypic variation between naturally co-existing genotypes of a Lepidopteran baculovirus.
EVOLUTIONARY ECOLOGY RESEARCH,
3(6), 687-701.
Author URL.
2000
Hodgson, D.J. (2000). Monoclonal aphid colonies and the measurement of clonal fitness. Ecological Entomology, 26: 444-448
1999
Hodgson DJ, Godfray HCJ (1999). The consequences of clustering by <i>Aphis fabae</i> foundresses on spring migrant production.
OECOLOGIA,
118(4), 446-452.
Author URL.
1996
Morton RH, Hodgson DJ (1996). The relationship between power output and endurance: a brief review. European Journal of Applied Physiology and Occupational Physiology, 73, 491-502.
