Publications by year
In Press
Fuster F, Kaiser-Bunbury CN, Olesen JM, Traveset A (In Press). Global patterns of the double mutualism phenomenon. Ecography
Kaiser-Bunbury CN (In Press). Restoring plant-pollinator communities: using a network approach to monitor pollination function. Island Invasives.
2023
Lonighi A (2023). Effects of non-native species and ecological restoration on network structure and ecosystem function.
Abstract:
Effects of non-native species and ecological restoration on network structure and ecosystem function
Non-native species pose a signi cant threat to biotic interactions, such as plantpollinators,
and associated ecosystem functions. Ecological restoration is commonly
used to mitigate or revert the impact of non-native species. The removal of nonnative
plants is one frequently used restoration approach to minimise competition
for resources between native and non-native plants, which facilitates the recovery
of native plant communities. Many aspects of how ecological restoration impacts
native ecosystems are not well understood. For example, the conditions that allow
ecological communities to thrive after restoration can take years to develop. Although
restoration interventions ideally aim to address most impacts of non-native
species, we know little about the response of non-target species, both native and
non-native.
In this thesis, I explore the effects of non-native species and ecological restoration on
plant-pollinator communities and pollination function on the island of Mahé, Seychelles,
in the Western Indian Ocean. I used a community-level restoration experiment
with honey bee (Apis mellifera) supplementation to study the medium-term
responses of plant-pollinator interaction networks to management interventions. Initial
restoration took place in 2011, and the datasets used here were collected across
two consecutive years (2018/19 and 2019/20).
Abstract.
Costa A, Heleno R, Freide EF, Dufrene Y, Huckle E, Kaiser-Bunbury CN (2023). Impacts of invasive ants on pollination of native plants are similar in invaded and restored plant communities. Global Ecology and Conservation, 42, e02413-e02413.
Gao E, Ma H, Yang T, Kaiser-Bunbury CN, Zhao Z (2023). Meadow transformations alter above- and below-ground ecological networks and ecosystem multifunctionality.
Functional Ecology,
37(6), 1703-1716.
Abstract:
Meadow transformations alter above- and below-ground ecological networks and ecosystem multifunctionality
Human-mediated environmental change transforms ecosystems worldwide. Understanding the detailed impact of these unprecedented changes on biodiversity and ecosystem functioning, however, is challenging. Meadow ecosystems on the Tibetan Plateau transform as a result of climate change and anthropogenic disturbances. Evaluating the consequences of these meadow transformations on above- and below-ground community structure, ecological network and ecosystem functioning is critical for predicting the impact on biodiversity and developing mitigation strategies. Here, we used a natural experiment across replicated sites to assess the responses of ecological networks of soil microbial communities and plant-pollinator communities to meadow transformations and investigate the impacts of these changes on ecosystem multifunctionality. As a result of swampy meadow desiccation, species richness and ecological network complexity at multiple trophic levels increased, pollination networks became more robust while soil microbial networks became more vulnerable to species loss. Pollination function appeared to benefit from increased diversity in resources and the formation of dry soil, but important below-ground functions decreased. When alpine meadows degraded further because of extensive grazing pressure, above-ground diversity and network complexity tended to decline. Soil microbial richness and composition remained unchanged but associations among soil microbes homogenized, and ecosystem productivity and pollination function decreased. Our study provides empirical evidence that human-mediated meadow transformations influence above- and below-ground ecological networks and ecosystem functioning simultaneously. The findings highlight that ecosystem transformations can have contrasting effects on above- and below-ground diversity and ecological networks, as well as ecosystem functions. Such contrasting responses call for targeted and nuanced management strategies to conserve biodiversity and ecosystem functioning in the Tibetan Plateau. Read the free Plain Language Summary for this article on the Journal blog.
Abstract.
Song C, Simmons BI, Fortin M-J, Gonzalez A, Kaiser-Bunbury CN, Saavedra S (2023). Rapid monitoring of ecological persistence.
Proceedings of the National Academy of Sciences,
120(20).
Abstract:
Rapid monitoring of ecological persistence
Effective conservation of ecological communities requires accurate and up-to-date information about whether species are persisting or declining to extinction. The persistence of an ecological community is supported by its underlying network of species interactions. While the persistence of the network supporting the whole community is the most relevant scale for conservation, in practice, only small subsets of these networks can be monitored. There is therefore an urgent need to establish links between the small snapshots of data conservationists can collect, and the “big picture” conclusions about ecosystem health demanded by policymakers, scientists, and societies. Here, we show that the persistence of small subnetworks (motifs) in isolation—that is, their persistence when considered separately from the larger network of which they are a part—is a reliable probabilistic indicator of the persistence of the network as a whole. Our methods show that it is easier to detect if an ecological community is not persistent than if it is persistent, allowing for rapid detection of extinction risk in endangered systems. Our results also justify the common practice of predicting ecological persistence from incomplete surveys by simulating the population dynamics of sampled subnetworks. Empirically, we show that our theoretical predictions are supported by data on invaded networks in restored and unrestored areas, even in the presence of environmental variability. Our work suggests that coordinated action to aggregate information from incomplete sampling can provide a means to rapidly assess the persistence of entire ecological networks and the expected success of restoration strategies.
Abstract.
2022
Vollstädt MGR, Galetti M, Kaiser-Bunbury CN, Simmons BI, Gonçalves F, Morales-Pérez AL, Navarro L, Tarazona-Tubens FL, Schubert S, Carlo T, et al (2022). Plant–frugivore interactions across the Caribbean islands: Modularity, invader complexes and the importance of generalist species.
Diversity and Distributions,
28(11), 2361-2374.
Abstract:
Plant–frugivore interactions across the Caribbean islands: Modularity, invader complexes and the importance of generalist species
Aim: Mutualistic interactions between plants and animals are fundamental for the maintenance of natural communities and the ecosystem services they provide. However, particularly in human-dominated island ecosystems, introduced species may alter mutualistic interactions. Based on an extensive dataset of plant–frugivore interactions, we mapped and analysed a meta-network across the Caribbean archipelago. Specifically, we searched for subcommunity structure (modularity) and identified the types of species facilitating the integration of introduced species in the Caribbean meta-network. Location: Caribbean archipelago (Lucayan archipelago, Greater Antilles, Lesser Antilles). Methods: We reviewed published scientific literature, unpublished theses and other nonpeer-reviewed sources to compile an extensive dataset of plant–frugivore interactions. We visualized spatial patterns and conducted a modularity analysis of the cross-island meta-network. We also examined which species were most likely to interact with introduced species: (1) endemic, nonendemic native or introduced species, and (2) generalized or specialized species. Results: We reported 3060 records of interactions between 486 plant and 178 frugivore species. The Caribbean meta-network was organized in 13 modules, driven by a combination of functional or taxonomic (modules dominated by certain groups of frugivores) and biogeographical (island-specific modules) mechanisms. Few introduced species or interaction pairs were shared across islands, suggesting little homogenization of the plant–frugivore meta-network at the regional scale. However, we found evidence of “invader complexes,” as introduced frugivores were more likely to interact with introduced plants than expected at random. Moreover, we found generalist species more likely to interact with introduced species than were specialized species. Main conclusions: These results demonstrate that generalist species and “invader complexes” may facilitate the incorporation of introduced species into plant–frugivore communities. Despite the influx of introduced species, the meta-network was structured into modules related to biogeographical and functional or taxonomic affinities. These findings reveal how introduced species become an integral part of mutualistic systems on tropical islands.
Abstract.
Song C, Simmons BI, Fortin M-J, Gonzalez A, Kaiser-Bunbury CN, Saavedra S (2022). Rapid monitoring for ecological persistence.
Costa A, Heleno R, Dufrene Y, Huckle E, Gabriel R, Harrison X, Schabo DG, Farwig N, Kaiser‐Bunbury CN (2022). Seasonal variation in impact of non‐native species on tropical seed dispersal networks.
Functional Ecology,
36(11), 2713-2726.
Abstract:
Seasonal variation in impact of non‐native species on tropical seed dispersal networks
Abstract
Invasive non‐native species can alter animal‐mediated seed dispersal interactions and ultimately affect the stability of recipient communities. The degree of such disturbances, however, is highly variable and depends on several factors, two of which have received little attention: the relative timing of native and non‐native fruiting phenologies, and the associated variation in relative resource availability across the fruiting period. Both are likely to alter plant–seed disperser interactions threatened by biological invasions.
Here we investigated the impact of plant invasions on the seasonal dynamics of frugivory and seed dispersal networks across a large‐scale experimental setup and a plant invasion gradient on a tropical island. We recorded fruit and frugivore abundances, and plant–frugivore interactions across eight inselbergs (i.e. rocky outcrops) with different levels of plant invasion during 10 months on the island of Mahé, Seychelles. By combining four sampling methods of plant–frugivore interactions we constructed quantitative seed dispersal networks at all sites across two 5‐month seasons: the on‐peak and off‐peak fruiting season.
Our findings showed that, by fruiting mostly synchronously with natives, non‐native plants compete with natives for dispersal services, predominantly carried out by native frugivores. Variation in native seed dispersal was driven by plant invasion and seasonality. Specifically, native seed dispersal declined with the degree of invasion; dispersal frequency increased with fruit abundance more strongly during the off‐peak fruiting season; and networks became increasingly specialised during off‐peak. These results indicated that during the main fruiting peak seed dispersal services were saturated, which likely intensified the competition between native and non‐native fruits. When resources were scarce during off‐peak fruiting season, native and non‐native frugivores were more selective in their fruit choice at sites dominated by non‐native plants.
We showed that native plant and frugivore populations and native seed dispersal interactions were more vulnerable in invaded plant communities, where non‐native plants compete with natives for dispersal services potentially reducing native recruitment. As invasive non‐native plants dominate many ecosystems world‐wide, particularly on islands, our findings showed that controlling plant invasions in vulnerable native communities can be critical to maintain native ecosystem functions and biodiversity.
Read the free Plain Language Summary for this article on the Journal blog.
Abstract.
Costa A, Heleno R, Dufrene Y, Huckle E, Gabriel R, Doudee D, Kaiser‐Bunbury CN (2022). Seed dispersal by frugivores from forest remnants promotes the regeneration of adjacent invaded forests in an oceanic island. Restoration Ecology, 30(8).
Costa Lorenzo A (2022). Spatio-temporal responses of ecosystem functions to ecological restoration.
Abstract:
Spatio-temporal responses of ecosystem functions to ecological restoration
Island ecosystems are vulnerable to the impacts of invasive non-native species. Non-native plant invasions often modify the structure and compromise the stability of recipient communities. To mitigate or revert the effects of invasive species on island biota, various strategies of invasive species control and ecological restoration (e.g. removal of non-native plant species) are being used on many islands worldwide. To develop and implement appropriate management strategies, it is critical to quantitatively assess the effects of the management intervention on ecosystem structure and functioning. This thesis uses a network approach and an established large-scale restoration experiment in a natural island ecosystem to investigate the longer-term (>5 years) responses of native mutualistic (seed-dispersal) and antagonistic (pre-dispersal seed predation and plant-pollinator antagonist) interactions to the removal of non-native plant species (i.e. restoration). The research was conducted on eight mountaintops (4 restored and 4 unrestored) of ca. 1 ha on the island of Mahé, Seychelles, in the Western Indian Ocean.
The thesis contains four data chapters based on four independent investigations. The first chapter investigates the role of inselberg forest remnants and frugivorous birds on the natural regeneration of surrounding invaded forests. We show that native forest remnants, by providing a source of native seeds for dispersal and recruitment, can facilitate the natural regeneration of adjacent invaded forests mediated by native frugivores, which may promote the resistance of these patches and their surroundings to plant invasions.
The second chapter explores the seasonal variation in the impact of non-native plant species on frugivory and seed dispersal networks in restored and unrestored plant communities. Our findings highlighted marked variations in the effects of non-native plants on seed dispersal interactions with seasonality and plant invasion. Frugivore foraging behaviour changed with the availability of resources in invaded, but not in restored plant communities. Plant invasion therefore has a direct negative impact on frugivores and native seed dispersal, and restoration can buffer against seasonal variation in resource constraints.
In the third chapter I use interaction networks on pre-dispersal seed predation to investigate the effects of restoration on seed predator insect assemblages. Restored communities supported a more diverse seed-predator insect community, which suggested that the homogenisation process of the ecosystem caused by plant invasions is in parts revertible. Restoration therefore appears to preserve the native seed-predator insects and their interactions with native plants.
Finally, I experimentally quantified the impact of two invasive ant species on the pollination and plant reproduction of four native plant species and assessed whether these effects differed with restoration. Ants contributed marginally to pollination of the native plants, but aggressive behaviour by invasive ants reduced flower visitations by flying pollinators, thereby potentially negatively affecting plant reproductive success. These effects were similar in restored and unrestored sites.
This thesis provides clear evidence on the importance of restoring native remnant forest patches, such as those on mountaintops on the island of Mahé, to maintain native plant communities and the functioning of these unique ecosystems through the conservation of seed dispersal interactions, insect diversity and pollination. These findings can be used to guide future management strategies that aim to achieve the conservation and restoration of native biodiversity and ecosystem functioning.
Abstract.
2021
Thurstan R, Hockings K, Hedlund J, Bersacola E, Collins C, Early R, Harrison M, Kaiser-Bunbury C, Nuno A, Van Veen F, et al (2021). Envisioning a resilient future for biodiversity conservation in the wake of the COVID-19 pandemic. People and Nature
Healy W (2021). How Degradation Type Impacts Natural Regeneration in a Tropical Peat-Swamp Forest.
Abstract:
How Degradation Type Impacts Natural Regeneration in a Tropical Peat-Swamp Forest
Within the last few decades Southeast Asian tropical peat-swamp forests have been increasingly better studied with greater understanding of their importance to global conservation. This rise in attention began towards the end of the 20th century as the scientific community started to recognise the vital role they play in global carbon storage and other ecosystem services. Now, this forest ecosystem is known to harbour diverse fauna and flora populations, some of which are the last remaining strongholds of highly threatened species. Despite this, tropical peat-swamp forests are being severely degraded due to widespread logging, yearly forest fires, and unregulated land conversion. This has led to a significant reduction in the remaining area of pristine forest, as well as globally significant carbon emissions, and many peatlands are now covered only by patchy, degraded forest or pioneer vegetation communities. With degradation set to continue, it is vital to improve our understanding of how these degraded peatlands will change over time and determine how to restore tropical peat-swamp forest communities.
Chapter one investigates whether tropical peat-swamp forest vegetation is capable of regenerating naturally in a protected but previously degraded forest. The vegetation communities in the logged and burned areas, within the recovering Sebangau forest, were surveyed and compared to the undisturbed forest to identify the severity to which they have been altered. The results suggest that regeneration potential is highly dependent on the type is degradation faced, with selectively logged forest showing many signs of positive regeneration after just 15 years. Conversely, vegetation surveys in two burned forest areas, 4 years and 14 years post-fire, show that regeneration is greatly inhibited and without assistance these sites will remain low in diversity and plant cover.
Chapter two builds on the findings of the previous chapter by examining how faunal biodiversity responds to the aforementioned degradation. This study surveyed the fruit-feeding butterfly population in the selectively logged, relatively undisturbed, and 4 years post-fire forest area, over a full year, as this taxonomic group is a useful indicator of a habitat’s wider biodiversity. The results were congruent with those in chapter one, as the selectively logged forest contained a population with highly similar abundance, species richness, and composition as recorded in the relatively undisturbed forest. Whereas surveys in the burned forest show an almost complete loss of butterflies, indicating a significant loss of fauna diversity.
Overall, this thesis draws two main conclusions which both have large implications for the conservation of the tropical peat-swamp forest ecosystem. Firstly, selectively logged forests are capable of regenerating naturally, and if further degradation can be prevented these areas can have significant conservation value, especially when considering the lack of pristine forest. Secondly, burned tropical peatlands show little capability of natural regeneration and are likely to be inhospitable for the region’s fauna. Therefore, significant assistance will be required to restore forest cover, prevent further carbon emissions, and help conserve many threatened species.
Abstract.
Gao E, Wang Y, Bi C, Kaiser-Bunbury CN, Zhao Z (2021). Restoration of Degraded Alpine Meadows Improves Pollination Network Robustness and Function in the Tibetan Plateau.
Frontiers in Ecology and Evolution,
9Abstract:
Restoration of Degraded Alpine Meadows Improves Pollination Network Robustness and Function in the Tibetan Plateau
Ecological restoration is widely used to mitigate the negative impacts of anthropogenic activities. There is an increasing demand to identify suitable restoration management strategies for specific habitat and disturbance types to restore interactions between organisms of degraded habitats, such as pollination. In the Tibetan Plateau, alpine meadows have suffered severe degradation due to overgrazing and climate change. Protecting vegetation by fencing during the growing season is a widely applied management regime for restoration of degraded grasslands in this region. Here, we investigated the effect of this restoration strategy on plant–pollinator communities and plant reproduction in the eastern Tibetan Plateau. We collected interaction and seed set data monthly across three grazed (grazed all year) and three ungrazed (fenced during growing season) alpine meadows in growing seasons of two consecutive years. We found ungrazed meadows produced more flowers and attracted more pollinator visits. Many common network metrics, such as nestedness, connectance, network specialization, and modularity, did not differ between grazing treatments. However, plants in ungrazed meadows were more robust to secondary species extinction than those in grazed meadows. The observed changes in the networks corresponded with higher seed set of plants that rely on pollinators for reproduction. Our results indicate that protection from grazing in growing seasons improves pollination network stability and function and thus is a viable restoration approach for degraded meadows.
Abstract.
CaraDonna PJ, Burkle LA, Schwarz B, Resasco J, Knight TM, Benadi G, Blüthgen N, Dormann CF, Fang Q, Fründ J, et al (2021). Seeing through the static: the temporal dimension of plant–animal mutualistic interactions.
Ecology Letters,
24(1), 149-161.
Abstract:
Seeing through the static: the temporal dimension of plant–animal mutualistic interactions
Most studies of plant–animal mutualistic networks have come from a temporally static perspective. This approach has revealed general patterns in network structure, but limits our ability to understand the ecological and evolutionary processes that shape these networks and to predict the consequences of natural and human-driven disturbance on species interactions. We review the growing literature on temporal dynamics of plant–animal mutualistic networks including pollination, seed dispersal and ant defence mutualisms. We then discuss potential mechanisms underlying such variation in interactions, ranging from behavioural and physiological processes at the finest temporal scales to ecological and evolutionary processes at the broadest. We find that at the finest temporal scales (days, weeks, months) mutualistic interactions are highly dynamic, with considerable variation in network structure. At intermediate scales (years, decades), networks still exhibit high levels of temporal variation, but such variation appears to influence network properties only weakly. At the broadest temporal scales (many decades, centuries and beyond), continued shifts in interactions appear to reshape network structure, leading to dramatic community changes, including loss of species and function. Our review highlights the importance of considering the temporal dimension for understanding the ecology and evolution of complex webs of mutualistic interactions.
Abstract.
Luker S (2021). The role of non-native plants in the integration of non-native phytophagous invertebrates in native food webs.
Abstract:
The role of non-native plants in the integration of non-native phytophagous invertebrates in native food webs
This thesis brings together a series of studies, examining the role of non-native plants in the integration of non-native invertebrates in native food webs. I use data from comprehensive surveys of formally-planted gardens to investigate the efficacy of straightforward measures of non-native plant presence and/or landscape parameters, as reliable predictors of non-native invertebrate presence, finding that non-native invertebrate richness increases with non-native plant species richness, with invertebrates showing a clear preference for woody plants. I then use the context of metapopulation theory to explore the facilitative role of non-native plants in the ability of a non-native invertebrate to persist within a community, finding that where host-plant habitat patches are closer together, the likelihood of a patch being occupied is greater, especially if the patch is occupied but that this effect is not universal, with species-specific effects present also. I then explore the potential for apparent competition, in the form of negative indirect interactions between native and non-native plants mediated by a shared invertebrate enemy, with the indirect interactions biased by plant relatedness, finding that phylogenetically ranked pairwise native/non-native plant interactions are weakly correlated with observed shared invertebrate interactions, while a significant Mantel test result indicates a significant potential for apparent competition. Finally, I test for detectability of apparent competition in a gall wasp community, finding no evidence of apparent competition but potential evidence for the unexpected occurrence of apparent mutualism. Collectively, these findings provide original insight into how non-native plants and non-native invertebrates interact in an ecological community, and how these interactions help to structure the community. Additionally, they have implications for non-native invertebrate species management, from the practical application of ground-level planting decisions to the development of reliable predictive tools.
Abstract.
2020
Fuster F, Kaiser‐Bunbury CN, Traveset A (2020). Pollination effectiveness of specialist and opportunistic nectar feeders influenced by invasive alien ants in the Seychelles.
American Journal of Botany,
107(7), 957-969.
Abstract:
Pollination effectiveness of specialist and opportunistic nectar feeders influenced by invasive alien ants in the Seychelles
PremiseOpportunistic nectar‐feeders may act as effective pollinators; nonetheless, we still lack information on whether these opportunistic species differ in their pollination effectiveness from specialized nectarivorous vertebrates and insects. Many nectar specialists have coevolved with the plants on which they feed; therefore, we would expect higher pollination effectiveness in specialists than in opportunistic feeders. Here, we assessed quantity and quality components of pollination effectiveness in specialist and opportunistic vertebrate nectarivores and insects, focusing on three plants from the Seychelles: Thespesia populnea, Polyscias crassa, and Syzygium wrightii.MethodsWe determined the quantity component (QNC) of pollination effectiveness with pollinator observations, and the quality component (QLC) by measuring fruit and seed set resulting from single visits by each pollinator. To detect potential negative effects of invasive ants on native plant‐pollinator interactions, we classified pollinator visits (quantity component) as disturbed (>6 ants/30 min) vs. undisturbed.ResultsAll focal plants were visited by insects, and vertebrate specialist and opportunist nectarivores, yet their pollination effectiveness differed. Flying insects were the most effective pollinators of T. populnea. The other two plants were most effectively pollinated by vertebrates; i.e. sunbirds (nectar specialists) in S. wrightii and Phelsuma geckos (nectar opportunists) in P. crassa, despite marked variation in QNC and QLC. Ant presence was associated with lower pollinator visitation rate in P. crassa and S. wrightii.ConclusionsOur study highlights the importance of all pollinator guilds, including opportunist nectarivorous vertebrates as pollinators of island plants, and the vulnerability of such interactions to disruption by nonnative species.
Abstract.
Kaiser-Bunbury CN, Simmons BI (2020). Restoration of pollination interactions in communities invaded by non-native plants. In (Ed) Plant invasions: the role of biotic interactions, 377-390.
Kaiser-Bunbury CN, Simmons BI (2020). Restoration of pollination interactions in communities invaded by non-native plants. In (Ed) Plant invasions: the role of biotic interactions, 377-390.
Schwarz B, Vázquez DP, CaraDonna PJ, Knight TM, Benadi G, Dormann CF, Gauzens B, Motivans E, Resasco J, Blüthgen N, et al (2020). Temporal scale-dependence of plant–pollinator networks.
Oikos,
129(9), 1289-1302.
Abstract:
Temporal scale-dependence of plant–pollinator networks
The study of mutualistic interaction networks has led to valuable insights into ecological and evolutionary processes. However, our understanding of network structure may depend upon the temporal scale at which we sample and analyze network data. To date, we lack a comprehensive assessment of the temporal scale-dependence of network structure across a wide range of temporal scales and geographic locations. If network structure is temporally scale-dependent, networks constructed over different temporal scales may provide very different perspectives on the structure and composition of species interactions. Furthermore, it remains unclear how various factors – including species richness, species turnover, link rewiring and sampling effort – act in concert to shape network structure across different temporal scales. To address these issues, we used a large database of temporally-resolved plant–pollinator networks to investigate how temporal aggregation from the scale of one day to multiple years influences network structure. In addition, we used structural equation modeling to explore the direct and indirect effects of temporal scale, species richness, species turnover, link rewiring and sampling effort on network structural properties. We find that plant–pollinator network structure is strongly temporally-scale dependent. This general pattern arises because the temporal scale determines the degree to which temporal dynamics (i.e. phenological turnover of species and links) are included in the network, in addition to how much sampling effort is put into constructing the network. Ultimately, the temporal scale-dependence of our plant–pollinator networks appears to be mostly driven by species richness, which increases with sampling effort, and species turnover, which increases with temporal extent. In other words, after accounting for variation in species richness, network structure is increasingly shaped by its underlying temporal dynamics. Our results suggest that considering multiple temporal scales may be necessary to fully appreciate the causes and consequences of interaction network structure.
Abstract.
2019
Russell JC, Kaiser-Bunbury CN (2019). Consequences of Multispecies Introductions on Island Ecosystems.
Annual Review of Ecology, Evolution, and Systematics,
50(1), 169-190.
Abstract:
Consequences of Multispecies Introductions on Island Ecosystems
the rate of non-native species introductions continues to increase, with directionality from continents to islands. It is no longer single species but entire networks of coevolved and newly interacting continental species that are establishing on islands. The consequences of multispecies introductions on the population dynamics and interactions of native and introduced species will depend on the form of trophic limitation on island ecosystems. Freed from biotic constraints in their native range, species introduced to islands no longer experience top-down limitation, instead becoming limited by and disrupting bottom-up processes that dominate on resource-limited islands. This framing of the ecological and evolutionary relationships among introduced species with one another and their ecosystem has important consequences for conservation. Whereas on continents the focus of conservation is on restoring native apex species and top-down limitation, on islands the focus must instead be on removing introduced animal and plant species to restore bottom-up limitation.
Abstract.
Morgan EJ, Kaiser-Bunbury CN, Edwards PJ, Scharmann M, Widmer A, Fleischer-Dogley F, Kettle CJ (2019). Identification of sex-linked markers in the sexually cryptic coco de mer: are males and females produced in equal proportions?.
AoB PLANTS,
12(1).
Abstract:
Identification of sex-linked markers in the sexually cryptic coco de mer: are males and females produced in equal proportions?
AbstractLodoicea maldivica (coco de mer) is a long-lived dioecious palm in which male and female plants are visually indistinguishable when immature, only becoming sexually dimorphic as adults, which in natural forest can take as much as 50 years. Most adult populations in the Seychelles exhibit biased sex ratios, but it is unknown whether this is due to different proportions of male and female plants being produced or to differential mortality. In this study, we developed sex-linked markers in Lodoicea using ddRAD sequencing, enabling us to reliably determine the gender of immature individuals. We screened 589 immature individuals to explore sex ratios across life stages in Lodoicea. The two sex-specific markers resulted in the amplification of male-specific bands (Lm123977 at 405 bp and Lm435135 at 130 bp). Our study of four sub-populations of Lodoicea on the islands of Praslin and Curieuse revealed that the two sexes were produced in approximately equal numbers, with no significant deviation from a 1:1 ratio before the adult stage. We conclude that sex in Lodoicea is genetically determined, suggesting that Lodoicea has a chromosomal sex determination system in which males are the heterogametic sex (XY) and females are homogametic (XX). We discuss the potential causes for observed biased sex ratios in adult populations, and the implications of our results for the life history, ecology and conservation management of Lodoicea.
Abstract.
Roberts B (2019). The hidden ecology of bumblebees: using classical and new methods to explore nest searching, floral resources and badger predation.
Abstract:
The hidden ecology of bumblebees: using classical and new methods to explore nest searching, floral resources and badger predation
Bumblebees provide a crucial ecosystem service, and are experiencing worldwide declines due to a number of stressors, such as habitat loss and climate change. Populations are regulated through ‘bottom-up’ (resources) and ‘top-down’ (pesticides, disease and predation) processes. Bumblebees have been widely researched, but there are still aspects of their ecology which are understudied due to the difficulties associated with researching them. This is the case for nest locations and nest predation. This thesis aims to uncover some of these hidden aspects of bumblebee ecology, through the development and implementation of new techniques: thermal cameras as a tool to locate bumblebee nests (Chapter 3), artificial nests to study badger predation rates (Chapter 4 & 5), and the utilisation of model simulations to look at the potential combined impacts of badger predation and food availability on bumblebee populations (Chapter 5). Thermal cameras were found to be unsuccessful, due to their small viewing areas. However the artificial nest method was shown to be a successful way of studying the relative differences in predation rates between habitats and geographic locations, with high predation of bumblebee nests in areas of high badger densities. Model simulations also showed that under high badger predation rates a simulated bumblebee population produced significantly fewer hibernating queens, workers, and colonies. Thus, novel research tools were found to be a useful way of monitoring the effects of top-down and bottom-up effects on bumblebee populations.
Alongside this, classical field techniques were used to study the use of botanical gardens and semi-natural farmland habitats by nest searching queens, and the foraging resources they provide across the flight season (Chapter 2). Residential gardens have been shown to be beneficial habitats for bumblebees, especially in urban environments. In Chapter 2 botanical gardens are looked at in a rural setting, which has not been done previously. Botanical gardens were found to contain a high number of nest searching queens, and experienced a peak of spring floral resources. However semi-natural habitats in farmland provided higher levels of floral resources in early and late summer. Therefore these two habitats may be providing complementary floral resources to pollinators. These results are discussed in terms of the importance of habitat heterogeneity for supporting pollinator populations.
Abstract.
2018
Ollerton J, Liede-Schumann S, Endress ME, Meve U, Rech AR, Shuttleworth A, Keller HA, Fishbein M, Alvarado-Cárdenas LO, Amorim FW, et al (2018). The diversity and evolution of pollination systems in large plant clades: Apocynaceae as a case study. Annals of Botany, 123(2), 311-325.
2017
Patiño J, Whittaker RJ, Borges PAV, Fernández-Palacios JM, Ah-Peng C, Araújo MB, Ávila SP, Cardoso P, Cornuault J, de Boer EJ, et al (2017). A roadmap for island biology: 50 fundamental questions after 50 years of the Theory of Island Biogeography.
Journal of Biogeography,
44(5), 963-983.
Abstract:
A roadmap for island biology: 50 fundamental questions after 50 years of the Theory of Island Biogeography
Aims: the 50th anniversary of the publication of the seminal book, the Theory of Island Biogeography, by Robert H. MacArthur and Edward O. Wilson, is a timely moment to review and identify key research foci that could advance island biology. Here, we take a collaborative horizon-scanning approach to identify 50 fundamental questions for the continued development of the field. Location: Worldwide. Methods: We adapted a well-established methodology of horizon scanning to identify priority research questions in island biology, and initiated it during the Island Biology 2016 conference held in the Azores. A multidisciplinary working group prepared an initial pool of 187 questions. A series of online surveys was then used to refine a list of the 50 top priority questions. The final shortlist was restricted to questions with a broad conceptual scope, and which should be answerable through achievable research approaches. Results: Questions were structured around four broad and partially overlapping island topics, including: (Macro)Ecology and Biogeography, (Macro)Evolution, Community Ecology, and Conservation and Management. These topics were then subdivided according to the following subject areas: global diversity patterns (five questions in total); island ontogeny and past climate change (4); island rules and syndromes (3); island biogeography theory (4); immigration–speciation–extinction dynamics (5); speciation and diversification (4); dispersal and colonization (3); community assembly (6); biotic interactions (2); global change (5); conservation and management policies (5); and invasive alien species (4). Main conclusions: Collectively, this cross-disciplinary set of topics covering the 50 fundamental questions has the potential to stimulate and guide future research in island biology. By covering fields ranging from biogeography, community ecology and evolution to global change, this horizon scan may help to foster the formation of interdisciplinary research networks, enhancing joint efforts to better understand the past, present and future of island biotas.
Abstract.
Kaiser-Bunbury CN, Blüthgen N, Junker R (2017). Biological invasions and ant-flower networks on islands. In Oliveira PS, Koptur S (Eds.)
Ant-Plant Interactions: Impacts of Humans on Terrestrial Ecosystems, Cambridge, UK: Cambridge University Press, 267-289.
Abstract:
Biological invasions and ant-flower networks on islands
Abstract.
Kaiser-Bunbury CN, Mougal J, Whittington AE, Valentin T, Gabriel R, Olesen JM, Blüthgen N (2017). Ecosystem restoration strengthens pollination network resilience and function.
Nature,
542(7640), 223-227.
Abstract:
Ecosystem restoration strengthens pollination network resilience and function
Land degradation results in declining biodiversity and the disruption of ecosystem functioning worldwide, particularly in the tropics. Vegetation restoration is a common tool used to mitigate these impacts and increasingly aims to restore ecosystem functions rather than species diversity. However, evidence from community experiments on the effect of restoration practices on ecosystem functions is scarce. Pollination is an important ecosystem function and the global decline in pollinators attenuates the resistance of natural areas and agro-environments to disturbances. Thus, the ability of pollination functions to resist or recover from disturbance (that is, the functional resilience) may be critical for ensuring a successful restoration process. Here we report the use of a community field experiment to investigate the effects of vegetation restoration, specifically the removal of exotic shrubs, on pollination. We analyse 64 plant-pollinator networks and the reproductive performance of the ten most abundant plant species across four restored and four unrestored, disturbed mountaintop communities. Ecosystem restoration resulted in a marked increase in pollinator species, visits to flowers and interaction diversity. Interactions in restored networks were more generalized than in unrestored networks, indicating a higher functional redundancy in restored communities. Shifts in interaction patterns had direct and positive effects on pollination, especially on the relative and total fruit production of native plants. Pollinator limitation was prevalent at unrestored sites only, where the proportion of flowers producing fruit increased with pollinator visitation, approaching the higher levels seen in restored plant communities. Our results show that vegetation restoration can improve pollination, suggesting that the degradation of ecosystem functions is at least partially reversible. The degree of recovery may depend on the state of degradation before restoration intervention and the proximity to pollinator source populations in the surrounding landscape. We demonstrate that network structure is a suitable indicator for pollination quality, highlighting the usefulness of interaction networks in environmental management.
Abstract.
Morgan EJ, Kaiser-Bunbury CN, Kettle CJ, Edwards PJ, Fleischer-Dogley F (2017). Keeping it in the family: strong fine-scale genetic structure and inbreeding in Lodoicea maldivica, the largest-seeded plant in the world.
Conservation Genetics,
18(6), 1317-1329.
Abstract:
Keeping it in the family: strong fine-scale genetic structure and inbreeding in Lodoicea maldivica, the largest-seeded plant in the world
The fine-scale spatial genetic structure (FSGS) of plant populations is strongly influenced by patterns of seed dispersal. An extreme case of limited dispersal is found in the charismatic yet endangered palm Lodoicea maldivica, which produces large fruits (up to 20 kg) dispersed only by gravity. To investigate patterns of seed dispersal and FSGS in natural populations we sampled 1252 individual adults and regenerating offspring across the species’ natural range in the Seychelles archipelago, and characterised their genotypes at 12 microsatellite loci. The average dispersal distance was 8.7 ± 0.7 m. Topography had a significant effect on seed dispersal, with plants on steep slopes exhibiting the longest distances. FSGS was intense, especially in younger cohorts. Contrary to what might be expected in a dioecious species, we found high levels of inbreeding, with most neighbouring pairs of male and female trees (≤10 m) being closely related. Nonetheless, levels of genetic diversity were relatively high and similar in the various sampling areas, although these differed in disturbance and habitat fragmentation. We discuss potential trade-offs associated with maternal resource provisioning of progeny, seed dispersal and inbreeding, and consider the implications of our findings for managing this globally significant flagship species.
Abstract.
Morgan EJ, Kaiser-Bunbury CN, Edwards PJ, Fleischer-Dogley F, Kettle CJ (2017). Tracing coco de mer's reproductive history: Pollen and nutrient limitations reduce fecundity.
Ecology and Evolution,
7(19), 7765-7776.
Abstract:
Tracing coco de mer's reproductive history: Pollen and nutrient limitations reduce fecundity
Habitat degradation can reduce or even prevent the reproduction of previously abundant plant species. To develop appropriate management strategies, we need to understand the reasons for reduced recruitment in degraded ecosystems. The dioecious coco de mer palm (Lodoicea maldivica) produces by far the largest seeds of any plant. It is a keystone species in an ancient palm forest that occurs only on two small islands in the Seychelles, yet contemporary rates of seed production are low, especially in fragmented populations. We developed a method to infer the recent reproductive history of female trees from morphological evidence present on their inflorescences. We then applied this method to investigate the effects of habitat disturbance and soil nutrient conditions on flower and fruit production. The 57 female trees in our sample showed a 19.5-fold variation in flower production among individuals over a seven-year period. Only 77.2% of trees bore developing fruits (or had recently shed fruits), with the number per tree ranging from zero to 43. Flower production was positively correlated with concentrations of available soil nitrogen and potassium and did not differ significantly between closed and degraded habitat. Fruiting success was positively correlated with pollen availability, as measured by numbers and distance of neighboring male trees. Fruit set was lower in degraded habitat than in closed forest, while the proportion of abnormal fruits that failed to develop was higher in degraded habitat. Seed size recorded for a large sample of seeds collected by forest wardens varied widely, with fresh weights ranging from 1 to 18 kg. Synthesis: Shortages of both nutrients and pollen appear to limit seed production of Lodoicea in its natural habitat, with these factors affecting different stages of the reproductive process. Flower production varies widely amongst trees, while seed production is especially low in degraded habitat. The size of seeds is also very variable. We discuss the implications of these findings for managing this ecologically and economically important species.
Abstract.
2016
Morgan EJ, Määttänen K, Kaiser-Bunbury CN, Buser A, Fleischer-Dogley F, Kettle CJ (2016). Development of 12 Polymorphic Microsatellite Loci for the Endangered Seychelles Palm Lodoicea maldivica (Arecaceae).
Applications in Plant Sciences,
4(4).
Abstract:
Development of 12 Polymorphic Microsatellite Loci for the Endangered Seychelles Palm Lodoicea maldivica (Arecaceae)
Premise of the study: the evolutionarily and ecologically distinct coco de mer palm Lodoicea maldivica (Arecaceae) is endemic to two islands in the Seychelles. Before colonization of the islands by man, the endangered palm formed large monodominant stands, but its natural range is now restricted to four main populations and several patches of isolated individuals. Microsatellite markers were designed to investigate the genetic structure of the remaining natural populations of L. maldivica. Methods and Results: We developed 12 polymorphic and three monomorphic microsatellite markers for this species, with a mean number of alleles per locus of 13.2 (range 5-21) and expected heterozygosity values ranging from 0.31-0.91 for the polymorphic loci. Conclusions: These markers enable us to study the patterns of genetic diversity, contemporary seed dispersal, and the fine-scale spatial genetic structure of this important conservation flagship species.
Abstract.
Rocha S, Perera A, Bunbury N, Kaiser-Bunbury CN, Harris DJ (2016). Speciation history and species-delimitation within the Seychelles Bronze geckos, Ailuronyx spp.: Molecular and morphological evidence.
Biological Journal of the Linnean SocietyAbstract:
Speciation history and species-delimitation within the Seychelles Bronze geckos, Ailuronyx spp.: Molecular and morphological evidence
© 2016 the Linnean Society of London. Research on the genetic variability across various organisms from the Seychelles granitic islands has revealed considerable differentiation within many taxa, often with deep evolutionary lineages, likely corresponding to cryptic species. Although an accurate description of insular diversity is important for biogeographical and conservation reasons, there is frequently a lack of information even for presumably better known groups, such as vertebrates. One example is the endemic genus Ailuronyx, which includes the emblematic Seychelles giant bronze gecko Ailuronyx trachygaster. In the present study, we investigate, for the first time, based on morphological and molecular information, the intraspecific diversity of the three currently recognized Ailuronyx species, and reassess their distribution and history of diversification. Our data clearly indicate an old (Miocenic) divergence between these species, as well as the existence of cryptic diversity within Ailuronyx seychellensis, and, to a lesser extent, within Ailuronyx tachyscopaeus, that should be further explored and described. Preliminary data suggest concordant patterns of morphological and molecular differentiation. The results also show that, although morphological discrimination between the currently described species is possible, some previous distribution records based on observations may be wrong, which is important for conservation management. The observed genetic structure patterns are congruent with those of other endemic taxa from the Seychelles, again highlighting the evolutionary importance of historical fragmentation across this ancient archipelago, the existence of overlooked diversity, and the need for detailed morphological and genetic assessments to accurately identify and address conservation priorities.
Abstract.
2015
Kaiser-Bunbury CN, Mougal J, Valentin T, Gabriel R, Blüthgen N (2015). Herbicide application as a habitat restoration tool: Impact on native island plant communities.
Applied Vegetation Science,
18(4), 650-660.
Abstract:
Herbicide application as a habitat restoration tool: Impact on native island plant communities
Questions: Which physical or chemical removal method is most effective in controlling woody invasive alien plant (IAP) species in sensitive conservation areas, while minimizing the impact on different life stages of native plant communities? is there a distinct influence of removal method on successional trajectories of post-treatment seedling communities? Location: Mid-altitude inselbergs, Mahé, Seychelles, Indian Ocean. Methods: We conducted two field experiments. First, to test the effects of four IAP control methods (cut, 5%, 10%, 15% Tordon 101 herbicide concentration) on ten woody IAP species, we treated a total of 320 adults and monitored mortality for 18 wk. Second, we set up five blocks each with four plots (4 m × 4 m) at three inselberg sites (N = 60 plots) and recorded the response of seedlings, saplings and adults of all native and IAP species to four Tordon 101 (a.i. picloram and 2,4-D) herbicide and manual control treatments (cut, cut-stump, foliar spray, control) over 22 mo. Treatment effects were analysed with GLMM models, and community responses were investigated with NMDS and multivariate ANOVA. Results: the first experiment showed that IAP mortality (98.3%) was similar across all three herbicide concentrations, but markedly higher than mortality of cut plants (42.5%). In the second experiment, abundance, but not diversity, of native seedlings declined with herbicide application in the first 6 mo after treatment. Ordination analysis showed that seedling communities experienced high turnover driven by early successional IAP species and abundance, and that between-plot variation was determined by site-specific differences, with only a weak treatment effect. Foliar spray resulted in high mortality of native saplings (52.7%) and adults (18.3%), and both herbicide applications reduced adult growth over a post-treatment period of 12 mo. Conclusion: IAP removal controlled plant invasion processes and altered community composition in the short term, regardless of removal method. Post-treatment trajectories of seedling communities are determined by site-specific differences. Chemicals can strongly increase the efficacy of IAP control, but short-term detrimental effects on native saplings and adults may be expected. As re-invasion by IAPs is likely, a long-term restoration plan is required. Management strategies that aim to conserve β-diversity should employ a landscape approach to habitat restoration to buffer against site idiosyncrasies.
Abstract.
Kaiser-Bunbury CN, Blüthgen N (2015). Integrating network ecology with applied conservation: a synthesis and guide to implementation.
AoB PLANTS,
7Abstract:
Integrating network ecology with applied conservation: a synthesis and guide to implementation
Ecological networks are a useful tool to study the complexity of biotic interactions at a community level. Advances in the understanding of network patterns encourage the application of a network approach in other disciplines than theoretical ecology, such as biodiversity conservation. So far, however, practical applications have been meagre. Here we present a framework for network analysis to be harnessed to advance conservation management by using plant-pollinator networks and islands as model systems. Conservation practitioners require indicators to monitor and assess management effectiveness and validate overall conservation goals. By distinguishing between two network attributes, the 'diversity' and 'distribution' of interactions, on three hierarchical levels (species, guild/ group and network) we identify seven quantitative metrics to describe changes in network patterns that have implications for conservation. Diversity metrics are partner diversity, vulnerability/generality, interaction diversity and interaction evenness, and distribution metrics are the specialization indices d' and H'2, and modularity. Distribution metrics account for sampling bias and may therefore be suitable indicators to detect human-induced changes to plant-pollinator communities, thus indirectly assessing the structural and functional robustness and integrity of ecosystems. We propose an implementation pathway that outlines the stages that are required to successfully embed a network approach in biodiversity conservation. Most importantly, only if conservation action and study design are aligned by practitioners and ecologists through joint experiments, are the findings of a conservation network approach equally beneficial for advancing adaptive management and ecological network theory. We list potential obstacles to the framework, highlight the shortfall in empirical, mostly experimental, network data and discuss possible solutions.
Abstract.
Kaiser-Bunbury CN (2015). Networks in island ecology: a synergistic approach to connect ecological theory with conservation application.
HabilitationAbstract:
Networks in island ecology: a synergistic approach to connect ecological theory with conservation application
Islands are ‘natural laboratories’ and ideal study sites to investigate the ecology and evolution of species, to examine macro-evolutionary processes, or to explain large-scale biogeographical patterns in biodiversity. Relative to their size, islands hold much of the world’s biodiversity; while at the same time native island biotas are severely threatened. The importance of islands for science, and the simultaneous risk of anthropogenic threats have made research and conservation of island biodiversity a high priority. As most ecological processes on islands are inevitably intertwined with human activity, ecological research on islands has strong practical and applied components. Equally, conservation and restoration on islands rely on ecological knowledge of species and ecosystems to achieve success.
Here, I present a series of publications that address basic and applied ecological questions in an island setting. Primarily, I study the consequences of biotic interactions on species persistence, and community structure and dynamics. My research is driven by the understanding that effective and successful conservation interventions and management strategies rely on a solid knowledge basis (i.e. ‘evidence-based conservation’), which thrives on synergies and close collaborations between ecologists and practitioners. Specifically, with the research I aim to: (1) further basic and applied knowledge on the structure, functioning and resilience of island ecosystems, using a community and interaction network approach; (2) develop new theoretical and applied approaches to incorporate ecological knowledge into biodiversity conservation; (3) communicate and interpret research findings for application by practitioners and decision-makers; and (4) actively guide and assist with the uptake of research findings in management.
in total, I present 14 publications falling within the four complementary areas of my research priorities. The publications are based on empirical data from islands (Seychelles and Mauritius, Indian Ocean) or specifically address aspects of ecology and conservation in an island context. Overall I apply an inter-disciplinary approach using islands as a model system to connect ecological research with conservation management, thus bridging the implementation gap.
the first pillar of my work aims to advance understanding of functional and mechanistic processes in mutualistic plant–animal interaction networks. Using the theoretical background of community ecology, we modelled the robustness of plant–pollinator communities to secondary extinction by incorporating pollinator behaviour. Further, we examined the impact of invasive alien plant species (i.e. a widespread threat to island ecosystems) on native plant–pollinator communities and pollinator functions. Following this, we identified the drivers of interaction dynamics, which is an important step towards recognising general patterns in pollination networks that can be used to predict network formation.
the theme of the second set of publications is the ecology and conservation of the iconic coco de mer palm Lodoicea maldivica, a keystone species and ecosystem engineer of the Seychelles’ endemic palm forest. This palm holds several botanical records and is critically important for Seychelles’ biodiversity and economy, which justifies prioritising L. maldivica research and management both nationally and internationally. Our research findings have resolved long-standing ecological and evolutionary peculiarities and have been the basis for the development of long-term national management strategies.
the third research pillar addresses the divide between ecological theory and applied conservation and restoration management, and presents solutions. We emphasise researchers’ responsibilities to go beyond the existing research framework and actively support the incorporation of research findings into applied conservation. While the above is exemplified with mutualistic plant–animal interactions and networks, the concepts are equally applicable in other fields.
the final theme incorporates a technical approach to applied ecological restoration by conducting field experiments on the efficacy of restoration intervention and the response of target and non-target species in different island settings. We present two case studies in which the conservation intervention was preceded by fully-replicated, randomised field experiments. The findings of the experiments were used to define best management practices for large-scale restoration and invasive plant eradication programmes.
all research themes are linked by applying a network approach to study biotic interactions, by combining ecological theory and management objectives, and using a collaborative approach to communication and research. This combined strategy has proved to be effective for resolving key questions and issues in island ecology.
Abstract.
Kaiser-Bunbury CN, Fleischer-Dogley F, Dogley D, Bunbury N (2015). Scientists' responsibilities towards evidence-based conservation in a Small Island Developing State. Journal of Applied Ecology, 52(1), 7-11.
Edwards PJ, Fleischer-Dogley F, Kaiser-Bunbury CN (2015). The nutrient economy of lodoicea maldivica, a monodominant palm producing the world's largest seed.
New Phytologist,
206(3), 990-999.
Abstract:
The nutrient economy of lodoicea maldivica, a monodominant palm producing the world's largest seed
The iconic Lodoicea maldivica palm appears to invest heavily in reproduction, with females bearing the world's largest seeds and males producing copious pollen. We asked how these palms, which grow in extremely poor soils, obtain sufficient nutrients to support such high levels of reproductive function. Our study site was the Vallée de Mai UNESCO Site on Praslin, Seychelles. We measured the trees' allocations of dry matter, nitrogen (N) and phosphorus (P) to aboveground growth and reproduction, quantified stemflow and throughfall, and measured availabilities of N and P in the soil. We show that the nutrient costs of reproduction are very high in male and female plants, and for P far exceed those of vegetative growth. We describe how the palm leaves form a huge funnel that intercepts particulate material, especially pollen, which is flushed to the base of the trunk when it rains. In this way, Lodoicea improves its nutrient supply and that of its dispersal-limited offspring. Lodoicea shares many functional characteristics with dominant trees of other monodominant forests in the humid tropics. It also exhibits unique features, including its huge seed, effective funnelling mechanism and diverse community of closely associated animals, suggesting a long evolutionary history under relatively stable conditions.
Abstract.
van Dinther M, Bunbury N, Kaiser-Bunbury CN (2015). Trial of herbicide control methods for sisal Agave sisalana in the arid Island environment of Aldabra atoll, Seychelles.
Conservation Evidence,
12, 14-18.
Abstract:
Trial of herbicide control methods for sisal Agave sisalana in the arid Island environment of Aldabra atoll, Seychelles
Sisal Agave sisalana is an invasive alien plant species of concern at the UNESCO World Heritage Site of Aldabra Atoll in the Seychelles. Physical control efforts since the 1970s to remove sisal from Aldabra have only been partially successful because the roots cannot be completely removed, resulting in continuous control efforts. We conducted a seven month herbicide trial, using different herbicide concentrations with two application methods, to determine the most effective and feasible control method for sisal. We also checked effects on surrounding native plants. The highest treatment mortality was from 50% herbicide concentration applied directly to the cut growth tip, which resulted in 80% sisal mortality after four months. Fewer treated plants died at lower herbicide concentrations and more small plants died than large plants. No sisal plant died that was foliar sprayed, only cut, or in the control group. There were no visible negative effects of any treatment on the surrounding native flora. The results indicate that chemical control of sisal is effective at high herbicide concentration applied directly to the cut growth tip. A full-scale eradication of sisal from Aldabra has been started based on the trial results.
Abstract.
2014
Senterre B, Kaiser-Bunbury CN (2014).
Conception of an integrated database on the flora, fauna and vegetation of the Seychelles. Government of Seychelles, Victoria, Seychelles, United Nations Development Programme.
Abstract:
Conception of an integrated database on the flora, fauna and vegetation of the Seychelles
Abstract.
Kaiser-Bunbury CN, Vázquez DP, Stang M, Ghazoul J (2014). Determinants of the microstructure of plant-pollinator networks.
Ecology,
95(12), 3314-3324.
Abstract:
Determinants of the microstructure of plant-pollinator networks
Identifying the determinants of biological interactions in mutualistic networks is key to understanding the rules that govern the organization of biodiversity. We used structural equation modeling and dissimilarities in nine ecological variables to investigate community processes underlying the turnover of species and their interaction frequencies (interaction pattern) among highly resolved plant-pollinator networks. Floral and pollinator community composition, i.e. species identities and their abundances, were strong determinants of the microstructure of pairwise interactions among the networks, explaining almost 69% of their variation. Flower and pollinator traits were directly related to interaction patterns, but were partly masked in the model by shared variance with community composition. Time of year and geographic location, floral and pollinator abundances independent of species identity, and relative abundance of exotic flowers had indirect and relatively weak effects on interaction patterns. Our analyses lead to precise predictions about the processes behind the interaction patterns in mutualistic networks. Future understanding of these processes will be aided by studies that evaluate these predictions experimentally at the network level.
Abstract.
Finger A, Kaiser-Bunbury CN, Kettle CJ, Valentin T, Ghazoul J (2014). Genetic connectivity of the moth pollinated tree Glionnetia sericeain a highly fragmented habitat.
PLoS ONE,
9(10).
Abstract:
Genetic connectivity of the moth pollinated tree Glionnetia sericeain a highly fragmented habitat
Long-distance gene flow is thought to be one prerequisite for the persistence of plant species in fragmented environments. Human influences have led to severe fragmentation of native habitats in the Seychelles islands, with many species surviving only in small and isolated populations. The endangered Seychelles endemic tree Glionnetia sericea is restricted to altitudes between 450 m and 900 m where the native forest vegetation has been largely lost and replaced with exotic invasives over the last 200 years. This study explores the genetic and ecological consequences of population fragmentation in this species by analysing patterns of genetic diversity in a sample of adults, juveniles and seeds, and by using controlled pollination experiments. Our results show no decrease in genetic diversity and no increase in genetic structuring from adult to juvenile cohorts. Despite significant inbreeding in some populations, there is no evidence of higher inbreeding in juvenile cohorts relative to adults. A Bayesian structure analysis and a tentative paternity analysis indicate extensive historical and contemporary gene flow among remnant populations. Pollination experiments and a paternity analysis show that Glionnetia sericea is self-compatible. Nevertheless, outcrossing is present with 7% of mating events resulting from pollen transfer between populations. Artificial pollination provided no evidence for pollen limitation in isolated populations. The highly mobile and specialized hawkmoth pollinators (Agrius convolvuli and Cenophodes tamsi; Sphingidae) appear to promote extensive gene flow, thus mitigating the potential negative ecological and genetic effects of habitat fragmentation in this species. We conclude that contemporary gene flow is sufficient to maintain genetic connectivity in this rare and restricted Seychelles endemic, in contrast to other island endemic tree species with limited contemporary gene flow.
Abstract.
Kaiser-Bunbury C, Cuthbert H, Fox R, Birch D, Bunbury N (2014). Invasion of yellow crazy ant Anoplolepis gracilipes in a Seychelles UNESCO palm forest. NeoBiota, 22, 43-57.
Kaiser-Bunbury CN, Senterre B (2014).
Manual on the Key Biodiversity Area CyberTracker application. Government of Seychelles, Victoria, Seychelles, United Nations Development Programme.
Abstract:
Manual on the Key Biodiversity Area CyberTracker application
Abstract.
Kueffer C, Kaiser-Bunbury CN (2014). Reconciling conflicting perspectives for biodiversity conservation in the Anthropocene.
Frontiers in Ecology and the Environment,
12(2), 131-137.
Abstract:
Reconciling conflicting perspectives for biodiversity conservation in the Anthropocene
We introduce a framework - based on experiences from oceanic islands - for conserving biodiversity in the Anthropocene. In an increasingly human-dominated world, the context for conservation-oriented action is extremely variable, attributable to three largely independent factors: the degree of anthropogenic change, the importance of deliberate versus inadvertent human influence on ecosystems, and land-use priorities. Given this variability, we discuss the need to integrate four strategies, often considered incompatible, for safeguarding biodiversity: maintaining relicts of historical biodiversity through intensive and continuous management; creating artificial in situ, inter situ, and ex situ conservation settings that are resilient to anthropogenic change; co-opting novel ecosystems and associated "opportunistic biodiversity" as the wildlands of the future; and promoting biodiversity in cultural landscapes by adapting economic activities. © the Ecological Society of America.
Abstract.
Carvalheiro LG, Biesmeijer JC, Benadi G, Fründ J, Stang M, Bartomeus I, Kaiser-Bunbury CN, Baude M, Gomes SIF, Merckx V, et al (2014). The potential for indirect effects between co-flowering plants via shared pollinators depends on resource abundance, accessibility and relatedness.
Ecology Letters,
17(11), 1389-1399.
Abstract:
The potential for indirect effects between co-flowering plants via shared pollinators depends on resource abundance, accessibility and relatedness
Co-flowering plant species commonly share flower visitors, and thus have the potential to influence each other's pollination. In this study we analysed 750 quantitative plant-pollinator networks from 28 studies representing diverse biomes worldwide. We show that the potential for one plant species to influence another indirectly via shared pollinators was greater for plants whose resources were more abundant (higher floral unit number and nectar sugar content) and more accessible. The potential indirect influence was also stronger between phylogenetically closer plant species and was independent of plant geographic origin (native vs. non-native). The positive effect of nectar sugar content and phylogenetic proximity was much more accentuated for bees than for other groups. Consequently, the impact of these factors depends on the pollination mode of plants, e.g. bee or fly pollinated. Our findings may help predict which plant species have the greatest importance in the functioning of plant-pollination networks.
Abstract.
2012
Hagen M, Kissling WD, Rasmussen C, De Aguiar MAM, Brown LE, Carstensen DW, Alves-Dos-Santos I, Dupont YL, Edwards FK, Genini J, et al (2012). 2 Biodiversity, Species Interactions and Ecological Networks in a Fragmented World. In (Ed) Global Change in Multispecies Systems Part 1, 89-210.
Hagen M, Kissling WD, Rasmussen C, De Aguiar MAM, Brown LE, Carstensen DW, Alves-Dos-Santos I, Dupont YL, Edwards FK, Genini J, et al (2012). Biodiversity, Species Interactions and Ecological Networks in a Fragmented World.
,
46, 89-210.
Abstract:
Biodiversity, Species Interactions and Ecological Networks in a Fragmented World
Biodiversity is organised into complex ecological networks of interacting species in local ecosystems, but our knowledge about the effects of habitat fragmentation on such systems remains limited. We consider the effects of this key driver of both local and global change on both mutualistic and antagonistic systems at different levels of biological organisation and spatiotemporal scales.There is a complex interplay of patterns and processes related to the variation and influence of spatial, temporal and biotic drivers in ecological networks. Species traits (e.g. body size, dispersal ability) play an important role in determining how networks respond to fragment size and isolation, edge shape and permeability, and the quality of the surrounding landscape matrix. Furthermore, the perception of spatial scale (e.g. environmental grain) and temporal effects (time lags, extinction debts) can differ markedly among species, network modules and trophic levels, highlighting the need to develop a more integrated perspective that considers not just nodes, but the structural role and strength of species interactions (e.g. as hubs, spatial couplers and determinants of connectance, nestedness and modularity) in response to habitat fragmentation.Many challenges remain for improving our understanding: the likely importance of specialisation, functional redundancy and trait matching has been largely overlooked. The potentially critical effects of apex consumers, abundant species and super-generalists on network changes and evolutionary dynamics also need to be addressed in future research. Ultimately, spatial and ecological networks need to be combined to explore the effects of dispersal, colonisation, extinction and habitat fragmentation on network structure and coevolutionary dynamics. Finally, we need to embed network approaches more explicitly within applied ecology in general, because they offer great potential for improving on the current species-based or habitat-centric approaches to our management and conservation of biodiversity in the face of environmental change. © 2012 Elsevier Ltd.
Abstract.
Finger A, Kaiser-Bunbury CN, Kettle CJ (2012). Development of polymorphic microsatellite markers of the Seychelles endemic tree Glionnetia sericea (Rubiaceae).
Conservation Genetics Resources,
4(2), 239-241.
Abstract:
Development of polymorphic microsatellite markers of the Seychelles endemic tree Glionnetia sericea (Rubiaceae)
Glionnetia sericea (Rubiaceae) is an endemic and rare tree species of the Seychelles, restricted to altitudes between 500 and 900 m with less than 1,000 remaining individuals. It survives in mist forests but also in smaller populations on granitic outcrops (inselbergs) and is pollinated by hawk moths which might ensure long-distance pollen flow. Understanding the reproductive ecology of this species will allow a better understanding on how such species survive in naturally fragmented habitats and will provide scientifically informed management recommendations. Here we report on ten species specific polymorphic microsatellite loci developed for a study of historic and contemporary gene flow. Based upon a sample of 81 adults, the number of alleles per locus ranged from 3 to 12 (mean of 6.1 per locus) with an average polymorphic information content of 0.52 across loci. Expected heterozygosity ranged from 0.27 to 0.82 with two of ten primers showing some deviation from Hardy-Weinberg expectation. © 2011 Springer Science+Business Media B.V.
Abstract.
Finger A, Kettle CJ, Kaiser-Bunbury CN, Valentin T, Mougal J, Ghazoul J (2012). Forest fragmentation genetics in a formerly widespread island endemic tree: Vateriopsis seychellarum (Dipterocarpaceae).
Molecular Ecology,
21(10), 2369-2382.
Abstract:
Forest fragmentation genetics in a formerly widespread island endemic tree: Vateriopsis seychellarum (Dipterocarpaceae)
Habitat fragmentation and changed land use have seriously reduced population size in many tropical forest tree species. Formerly widespread species with limited gene flow may be particularly vulnerable to the negative genetic effects of forest fragmentation and small population size. Vateriopsis seychellarum (Dipterocarpaceae) is a formerly widespread canopy tree of the Seychelles, but is now reduced to 132 adult individuals distributed in eleven sites. Using ten microsatellite loci, a genetic inventory of all adult trees and a sample of 317 progeny, we demonstrate that despite its restricted range, overall genetic diversity was relatively high (H E: 0.56). The juvenile cohort, however, had significantly lower allelic richness (adults R S: 3.91; juveniles R S: 2.83) and observed heterozygosity than adult trees (adults H O: 0.62; juveniles H O: 0.48). Rare alleles were fewer and kinship between individuals was stronger in juveniles. Significant fine-scale spatial genetic structure was observed in remnant adults, and parentage analysis indicated that more than 90% of sampled progeny disperse
Abstract.
Schleuning M, Fründ J, Klein AM, Abrahamczyk S, Alarcón R, Albrecht M, Andersson GKS, Bazarian S, Böhning-Gaese K, Bommarco R, et al (2012). Specialization of mutualistic interaction networks decreases toward tropical latitudes.
Current Biology,
22(20), 1925-1931.
Abstract:
Specialization of mutualistic interaction networks decreases toward tropical latitudes
Species-rich tropical communities are expected to be more specialized than their temperate counterparts [1-3]. Several studies have reported increasing biotic specialization toward the tropics [4-7], whereas others have not found latitudinal trends once accounting for sampling bias [8, 9] or differences in plant diversity [10, 11]. Thus, the direction of the latitudinal specialization gradient remains contentious. With an unprecedented global data set, we investigated how biotic specialization between plants and animal pollinators or seed dispersers is associated with latitude, past and contemporary climate, and plant diversity. We show that in contrast to expectation, biotic specialization of mutualistic networks is significantly lower at tropical than at temperate latitudes. Specialization was more closely related to contemporary climate than to past climate stability, suggesting that current conditions have a stronger effect on biotic specialization than historical community stability. Biotic specialization decreased with increasing local and regional plant diversity. This suggests that high specialization of mutualistic interactions is a response of pollinators and seed dispersers to low plant diversity. This could explain why the latitudinal specialization gradient is reversed relative to the latitudinal diversity gradient. Low mutualistic network specialization in the tropics suggests higher tolerance against extinctions in tropical than in temperate communities. © 2012 Elsevier Ltd.
Abstract.
2011
Finger A, Kettle CJ, Kaiser-Bunbury CN, Valentin T, Doudee D, Matatiken D, Ghazoul J (2011). Back from the brink: Potential for genetic rescue in a critically endangered tree.
Molecular Ecology,
20(18), 3773-3784.
Abstract:
Back from the brink: Potential for genetic rescue in a critically endangered tree
Rare plant species are vulnerable to genetic erosion and inbreeding associated with small population size and isolation due to increasing habitat fragmentation. The degree to which these problems undermine population viability remains debated. We explore genetic and reproductive processes in the critically endangered long-lived tropical tree Medusagyne oppositifolia, an endemic to the Seychelles with a naturally patchy distribution. This species is failing to recruit in three of its four populations. We evaluate whether recruitment failure is linked to genetic problems associated with fragmentation, and if genetic rescue can mitigate such problems. Medusagyne oppositifolia comprises 90 extant trees in four populations, with only the largest (78 trees) having successful recruitment. Using 10 microsatellite loci, we demonstrated that genetic diversity is high (H E: 0.48-0.63; H O: 0.56-0.78) in three populations, with only the smallest population having relatively low diversity (H E: 0.26 and H O: 0.30). All populations have unique alleles, high genetic differentiation, and significant within population structure. Pollen and seed dispersal distances were mostly less than 100 m. Individuals in small populations were more related than individuals in the large population, thus inbreeding might explain recruitment failure in small populations. Indeed, inter-population pollination crosses from the large donor population to a small recipient population resulted in higher reproductive success relative to within-population crosses. Our study highlights the importance of maintaining gene flow between populations even in species that have naturally patchy distributions. We demonstrate the potential for genetic and ecological rescue to support conservation of plant species with limited gene flow. © 2011 Blackwell Publishing Ltd.
Abstract.
Noble T, Bunbury N, Kaiser-Bunbury CN, Bell DJ (2011). Ecology and co-existence of two endemic day gecko (Phelsuma) species in Seychelles native palm forest.
Journal of Zoology,
283(1), 73-80.
Abstract:
Ecology and co-existence of two endemic day gecko (Phelsuma) species in Seychelles native palm forest
In island ecosystems, reptiles play diverse ecological roles as a result of niche broadening, which increases potential niche overlap between species. Ecological niche partitioning is a means of reducing direct competition between coexisting species and differences in habitat use among island gecko species have been suggested as a by-product of specialization to feeding on certain resources. Here, we examine modes and drivers of niche partitioning of two endemic species of Phelsuma gecko (Phelsuma sundbergi and Phelsuma astriata) in relict native palm forest in the Seychelles to further understanding of congeneric reptile co-existence in native habitats. Phelsuma abundance, microhabitat use and habitat composition were quantified in different macrohabitat types. P. sundbergi showed a clear preference for habitat dominated by the coco de mer palm, Lodoicea maldivica and a strong association with male individuals of this dioecious species. P. astriata density increased significantly with arboreal biodiversity but did not display a relationship with a specific tree type. High levels of resource segregation were determined along the microhabitat axis, based on differential tree preference. Our results suggest that P. sundbergi and P. astriata may have evolved to co-exist in this habitat type through partitioning of microhabitat as members of a divergent specialist/generalist assemblage determined by consumption of L. maldivica pollen by P. sundbergi. Our findings concur with the hypothesis that differences in habitat use among island reptiles are a by-product of trophic specialization and support the conservation of native habitat for maintenance of reptile diversity. © 2010 the Authors. Journal of Zoology © 2010 the Zoological Society of London.
Abstract.
Fleischer-Dogley F, Kettle CJ, Edwards PJ, Ghazoul J, Määttänen K, Kaiser-Bunbury CN (2011). Morphological and genetic differentiation in populations of the dispersal-limited coco de mer (Lodoicea maldivica): Implications for management and conservation.
Diversity and Distributions,
17(2), 235-243.
Abstract:
Morphological and genetic differentiation in populations of the dispersal-limited coco de mer (Lodoicea maldivica): Implications for management and conservation
Aims Developing plant conservation strategies requires knowledge of ecological and genetic processes underlying population dynamics. We aimed to quantify morphological and genetic differentiation among remnant populations of the iconic coco-de-mer palm Lodoicea maldivica. We hypothesized that limited gene flow among widely spaced populations would result in high genetic variation and large phenotypic differences among populations. Location Islands of Praslin and Curieuse (CU), Seychelles, Indian Ocean. Methods We conducted an extensive population survey and recorded morphological parameters for 447 Lodoicea in the main populations at Vallée de Mai (VM) and Fond Ferdinand (FF) on Praslin, and on CU. We collected leaf material from 180 trees in these populations for DNA genotyping using amplified fragment length polymorphisms. Results a total of 16,766 Lodoicea trees were recorded in the three populations (72.6% of Lodoicea on both islands). Lodoicea trees at VM and FF showed similar morphology, but differed in most parameters from those at CU, which were shorter, grew more slowly and produced fewer seeds. Mean overall genetic diversity was 0.337, and percentage of polymorphic loci was 91.1. Genetic diversity of the CU population was lower than that at VM and FF. There was weak genetic differentiation between CU and Praslin populations, but 99% of all genetic diversity was within populations. Main conclusions Trees on CU differed in growth and morphology from those of the two Praslin populations. These phenotypic differences, however, were not mirrored in the genetic structure of the populations. All populations were relatively genetically diverse with remarkably little differentiation among populations. This suggests that the capacity of Lodoicea to dominate across a range of habitats may be because of high phenotypic plasticity. High genetic connectivity may be maintained through long-distance wind pollination. Given the uncertainty about the extent of underlying adaptive variation, we recommend that restoration projects avoid transferring seeds between island populations. © 2010 Blackwell Publishing Ltd.
Abstract.
Kaiser-Bunbury CN, Valentin T, Mougal J, Matatiken D, Ghazoul J (2011). The tolerance of island plant-pollinator networks to alien plants.
Journal of Ecology,
99(1), 202-213.
Abstract:
The tolerance of island plant-pollinator networks to alien plants
Invasive alien plant species pose a severe threat to native plant communities world-wide, especially on islands. While many studies focus on the direct impact of alien plants on native systems, indirect effects of plant invaders on co-flowering natives, for example through competition for pollination services, are less well studied and the results are variable. We used six temporally and taxonomically highly resolved plant-pollinator networks from the island of Mahé, Seychelles, to investigate the indirect impact of invasive alien plant species on remnant native plant communities mediated by shared pollinators. We employed fully quantitative network parameters and information on plant reproductive success, and pollinator diversity and behaviour, to detect changes in plant-pollinator networks along an invasion gradient. The number of visits to and fruit set of native plants did not change with invasion intensity. Weighted plant linkage and interaction evenness, however, was lower at invaded sites than at less invaded sites. These patterns were primarily driven by shifts in interactions of the most common pollinator, the introduced honey bee Apis mellifera, while weak interactions and strong native interactions remained unchanged. Synthesis. The implications of these findings are twofold: first, quantitative network parameters are important tools for detecting underlying biological patterns. Secondly, alien plants and pollinators may play a greater role in shaping network structure at high than low levels of invasion. We could not show, however, whether the presence of invasive plants result in a simplification of plant-pollinator networks that is detrimental to native plants and pollinators alike. © 2010 the Authors. Journal of Ecology © 2010 British Ecological Society.
Abstract.
2010
Kaiser-Bunbury CN, Traveset A, Hansen DM (2010). Conservation and restoration of plant-animal mutualisms on oceanic islands.
Perspectives in Plant Ecology, Evolution and Systematics,
12(2), 131-143.
Abstract:
Conservation and restoration of plant-animal mutualisms on oceanic islands
Islands harbour much of the world's threatened biodiversity. Recent work has highlighted how it is not species diversity per se but rather the interactions between organisms that breathes life into ecosystems. Thus, the real challenge to preserving and restoring biodiversity on islands is not to only focus on species themselves, but more importantly on maintaining and restoring the integrity of interactions between the species. Here we argue that mutualistic plant-animal interactions play a pivotal role with regards to conservation and restoration on islands. Furthermore, these interactions are ideally suited for inter-island comparisons due to ecological and evolutionary similarities across geographical and taxonomical boundaries. The similarities include highly generalised mutualistic systems, the evolution and readjustment of plant reproductive traits, and a disharmony in taxonomic groups of mutualists, compared to continental ecosystems. We highlight past and present threats to island plant-animal mutualisms, as well as the challenges and opportunities inherent to these interactions. In particular, we (1) argue that mutualistic networks provide an ideal approach to collect information and advance our knowledge on the systems, (2) suggest the use of interactions as biodiversity monitoring and assessment tools, (3) highlight the differences and similarities between pollination and seed dispersal interactions in the context of restoration, and (4) briefly discuss the ambiguous role of alien invasive species in the management of mutualistic interactions. Finally, we highlight how a recently proposed but controversial restoration strategy, rewilding, can be gainfully applied to and further advanced in island settings. © 2009 Rübel Foundation, ETH Zürich.
Abstract.
Finger A, Ghazoul J, Todd M, Kaiser-Bunbury C, Kettle C (2010). Development of thirteen polymorphic microsatellite markers for the seychelles endangered and endemic jellyfish tree medusagyne oppositifolia (Medusagynaceae).
Conservation Genetics Resources,
2(SUPPL.1), 173-175.
Abstract:
Development of thirteen polymorphic microsatellite markers for the seychelles endangered and endemic jellyfish tree medusagyne oppositifolia (Medusagynaceae)
The jellyfish tree Medusagyne oppositifolia is a flagship species of the Seychelles, being not only extremely rare and critically endangered, but also representing a monospecific endemic family, Medusagynaceae. The species survives in four populations on the Island of Mahé, where the total number of reproductive adults is 89. Natural regeneration is only known for the largest of these populations. Understanding the mechanisms driving the lack of natural regeneration in this species has great conservation relevance. We developed thirteen polymorphic microsatellite loci for this species to enable studies of historic and contemporary gene flow. The number of alleles per locus ranged from 2 to 15 (mean of 6.62 per locus) with an average polymorphic information content of 0.54 across loci. Expected heterozygosity ranged from 0.12 to 0.66 with only two of the 13 loci showing deviation from Hardy-Weinberg expectation. The markers will help to provide a better understanding of the significance of historic distributions, gene flow and recent anthropogenic habitat degradation for the in situ and ex-situ conservation of this flagship tree species. © Springer Science+Business Media B.V. 2009.
Abstract.
Rist L, Kaiser-Bunbury CN, Fleischer-Dogley F, Edwards P, Bunbury N, Ghazoul J (2010). Sustainable harvesting of coco de mer, Lodoicea maldivica, in the Vallée de Mai, Seychelles.
Forest Ecology and Management,
260(12), 2224-2231.
Abstract:
Sustainable harvesting of coco de mer, Lodoicea maldivica, in the Vallée de Mai, Seychelles
The coco de mer palm Lodoicea maldivica, endemic to the Seychelles, is a flagship species for tourism and conservation. It bears the world's largest seed for which it is currently heavily exploited across its limited range, and it is clear that harvesting at current levels cannot be maintained indefinitely. Biologically informed harvesting protocols are therefore required to move towards sustainable management that secures the long-term viability of the population and the revenue that it currently generates. Demographic modelling using population matrix models is a useful tool in these efforts as it identifies both the life stages with the strongest influence on population dynamics as well as the consequences of current use intensities. Here we provide an initial population model based on data currently available to assess the status of the largest L. maldivica population in the Vallée de Mai World Heritage Site. We estimated transition probabilities and constructed matrices to estimate the populations' growth rate under current and alternative harvesting regimes, taking into account uncertainty regarding adult mortality and lifespan. Model projections of the population under current harvesting intensities forecast a marked decrease in the proportion of juveniles in the population and a gradually declining population over the next 200 years. Population growth rates were most sensitive to adult survival, reflecting the long generation time of this species and the remaining uncertainty in this respect. Based on this preliminary model we propose a precautionary sustainable harvesting limit for L. maldivica and discuss the challenges and opportunities of its management, including recommendations for future data collection. © 2010 Elsevier B.V.
Abstract.
Kaiser-Bunbury CN, Muff S, Memmott J, Müller CB, Caflisch A (2010). The robustness of pollination networks to the loss of species and interactions: a quantitative approach incorporating pollinator behaviour.
Ecology Letters,
13(4), 442-452.
Abstract:
The robustness of pollination networks to the loss of species and interactions: a quantitative approach incorporating pollinator behaviour
Species extinctions pose serious threats to the functioning of ecological communities worldwide. We used two qualitative and quantitative pollination networks to simulate extinction patterns following three removal scenarios: random removal and systematic removal of the strongest and weakest interactors. We accounted for pollinator behaviour by including potential links into temporal snapshots (12 consecutive 2-week networks) to reflect mutualists' ability to 'switch' interaction partners (re-wiring). Qualitative data suggested a linear or slower than linear secondary extinction while quantitative data showed sigmoidal decline of plant interaction strength upon removal of the strongest interactor. Temporal snapshots indicated greater stability of re-wired networks over static systems. Tolerance of generalized networks to species extinctions was high in the random removal scenario, with an increase in network stability if species formed new interactions. Anthropogenic disturbance, however, that promote the extinction of the strongest interactors might induce a sudden collapse of pollination networks. © 2010 Blackwell Publishing Ltd/CNRS.
Abstract.
2009
Kaiser-Bunbury CN, Memmott J, Müller CB (2009). Community structure of pollination webs of Mauritian heathland habitats.
Perspectives in Plant Ecology, Evolution and Systematics,
11(4), 241-254.
Abstract:
Community structure of pollination webs of Mauritian heathland habitats
Pollination webs have recently deepened our understanding of complex ecosystem functions and the susceptibility of biotic networks to anthropogenic disturbances. Extensive mutualistic networks from tropical species-rich communities, however, are extremely scarce. We present fully quantitative pollination webs of two plant-pollinator communities of natural heathland sites, one of which was in the process of being restored, on the oceanic island of Mauritius. The web interaction data cover a full flowering season from September 2003 to March 2004 and include all flowering plant and their pollinator species. Pollination webs at both sites were dominated by a few super-abundant, disproportionately well-connected species, and many rare and specialised species. The webs differed greatly in size, reflecting higher plant and pollinator species richness and abundance at the restored site. About one fifth of plant species at the smaller community received
Abstract.
Kaiser-Bunbury CN, Müller CB (2009). Indirect interactions between invasive and native plants via pollinators.
Naturwissenschaften,
96(3), 339-346.
Abstract:
Indirect interactions between invasive and native plants via pollinators
In generalised pollination systems, the presence of alien plant species may change the foraging behaviour of pollinators on native plant species, which could result in reduced reproductive success of native plant species. We tested this idea of indirect interactions on a small spatial and temporal scale in a field study in Mauritius, where the invasive strawberry guava, Psidium cattleianum, provides additional floral resources for insect pollinators. We predicted that the presence of flowering guava would indirectly and negatively affect the reproductive success of the endemic plant Bertiera zaluzania, which has similar flowers, by diverting shared pollinators. We removed P. cattleianum flowers within a 5-m radius from around half the B. zaluzania target plants (treatment) and left P. cattleianum flowers intact around the other half (control). By far, the most abundant and shared pollinator was the introduced honey bee, Apis mellifera, but its visitation rates to treatment and control plants were similar. Likewise, fruit and seed set and fruit size and weight of B. zaluzania were not influenced by the presence of P. cattleianum flowers. Although other studies have shown small-scale effects of alien plant species on neighbouring natives, we found no evidence for such negative indirect interactions in our system. The dominance of introduced, established A. mellifera indicates their replacement of native insect flower visitors and their function as pollinators of native plant species. However, the pollination effectiveness of A. mellifera in comparison to native pollinators is unknown. © 2008 Springer-Verlag.
Abstract.
2008
Kaiser CN, Hansen DM, Müller CB (2008). Exotic pest insects: another perspective on coffee and conservation. Oryx, 42(01).
Hansen DM, Kaiser CN, Müller CB (2008). Seed Dispersal and Establishment of Endangered Plants on Oceanic Islands: the Janzen-Connell Model, and the Use of Ecological Analogues. PLoS ONE, 3(5), e2111-e2111.
2007
Kaiser CN, Hansen DM, Müller CB (2007). Habitat Structure Affects Reproductive Success of the Rare Endemic Tree Syzygium mamillatum (Myrtaceae) in Restored and Unrestored Sites in Mauritius. Biotropica, 40(1), 84-96.
2006
Kaiser-Bunbury CN (2006). Functional integrity of plant-pollinator communities in restored habitats in Mauritius.
Abstract:
Functional integrity of plant-pollinator communities in restored habitats in Mauritius
This thesis investigates the effects of introduced plant and animal species on native mutualistic interactions, such as pollination and seed dispersal, in Mauritius. Most Mauritian ecosystems are highly degraded by invasive alien plant species, which pose a direct threat to native biodiversity. To conserve endemic plant species and reduce the risk of extinction, conservationists have established a habitat restoration scheme, which focuses on the eradication of introduced plants in fenced plots. However, both the consequences of this restoration for associated animal communities and the role of mutualists in fulfilling their previous ecosystem functions to ensure native plant reproduction are largely unknown.
Chapter 2: we studied the pollination ecology of the endangered endemic cauliflorous tree Syzygium mamillatum (Myrtaceae) in a restored forest and an adjacent area heavily degraded by invasive plant species. Flowers of S. mamillatum were only visited by generalist bird species. Although gross fruit and seed production of trees in the restored site exceeded those of the unrestored site, fruit and seed set was higher in the degraded forest. This corresponded to the higher bird visitation rate in the unrestored forest. The contrasting avian foraging behaviour may be explained by differences in habitat structure between sites. We conclude that restoration weeding can affect the pollination of S. mamillatum in the short-term.
Chapter 3: another critical stage in the plant reproduction cycle, which may be interrupted in degraded ecosystems, is the dispersal of propagules. We studied experimentally the effects of missing propagule dispersal on seed germination and seedling survival of S. mamillatum. Our findings provide the first evidence of the significance of the Janzen-Connell model for seedling establishment on an oceanic island. In addition, we demonstrated how ecological analogue species can be used to resurrect extinct seed dispersal interactions.
Chapter 4: we conducted a removal experiment to test whether the presence of the flowering, invasive strawberry guava Psidium cattleianum affects the reproductive performance of the neighbouring, endemic plant Bertiera zaluzania indirectly via shared pollinators. The introduced honey bee Apis mellifera was the most abundant pollinator of B. zaluzania. However, we recorded similar visitation rates, fruit set and seed set for B. zaluzania plants which were surrounded by P. cattleianum flowers and for those where P. cattleianum flowers had been removed. The absence of detectable indirect effects indicates minimal indirect competition for pollination between the introduced strawberry guava and B. zaluzania.
Chapter 5: we documented a strong negative effect of the introduced coffee pest Prophantis smaragdina on the reproductive success of the endangered Mauritian endemic plant Bertiera zaluzania. Most coffee agro-environmental studies focus on the benefits that coffee plants can derive from nearby natural habitats, and neglect to investigate the potential detrimental effects of coffee pest species invading these natural habitats. We present a new perspective to the ongoing scientific debate about coffee and the maintenance of biodiversity in the tropics.
Chapter 6: we used fully quantified flower visitation webs to investigate three main objectives; 1) to compare plant–pollinator community structure of restored and unrestored sites; 2) to identify keystone species of the webs and 3) to determine the effect of introduced species on community structure. Community structure was more complex in the restored than the unrestored site. Visitation webs from both sites were dominated by a few super-abundant, disproportionately-well connected plant and pollinator species, and many rare and specialised species. The dominance of these super-abundant, super-generalist keystone species may be critical, irrespective of their introduced/native status, for ecosystem stability and to ensure reproductive success of a wide range of native plant species. The low visitation rate of introduced plant species suggested a low level of indirect competition for pollination with native plant species. However, the infiltration of the local pollinator community by introduced flower visitors suggested strong competition between native and introduced pollinators for floral resources, which may have resulted in the displacement of native pollinators and consequently the disruption of co-evolved plant–pollinator interactions. For habitat restoration to be successful in the long-term, practitioners should maintain structural diversity to support a species-rich and abundant pollinator assemblage which ensures native plant reproduction.
Chapter 7: we compared flower visitation webs for 13 consecutive fortnightly periods from a restored and an unrestored site (see Chapter 6) and the three network properties connectance, degree distribution and nestedness to describe temporal and spatial variation in plant–pollinator systems and their network topologies. The latter has implications for the stability and the resilience of these networks to perturbations. We found large fluctuations in species diversity (i.e. network size), floral and pollinator abundance between fortnights and sites. The three network properties varied considerably among fortnightly networks and sites, implying that network structure and, thus, network stability and complexity, are not static throughout the season. This may have implications for those animal and plant species which are phenologically constrained to parts of the season when network stability is low, increasing their susceptibility to disturbance. Potential temporal fluctuation in a range of network properties should be taken into account in future network studies.
Abstract.
2002
Kaiser-Bunbury CN (2002). Influence of wind and pollen gathering by bees on reproductive success of the tropical grass Brachiaria platynota K. Schum. (Poaceae: Paniceae) at Kakamega Forest Nature Reserve, Kenya.
