Publications by year
In Press
Cresswell J (In Press). Moderate pollination limitation in some entomophilous crops of Europe.
Agriculture, Ecosystems and Environment Full text.
Cresswell JE (In Press). The effect of dietary neonicotinoid pesticides on non-flight thermogenesis in
worker bumble bees (Bombus terrestris).
Journal of Insect Physiology Full text.
2021
Stewart T, Bolton‐Patel N, Cresswell JE (2021). Eating versus heating: a study of the allocation of workers between foraging and nest incubation in bumble bees. Ecological Entomology
Cresswell J (2021). Eating versus heating: a study of the allocation of workers between foraging and nest incubation in bumble bees (dataset).
Abstract:
Eating versus heating: a study of the allocation of workers between foraging and nest incubation in bumble bees (dataset)
1. Bumble bees are important eusocial pollinators whose worker caste, fuelled by nectar sugar, accelerate colony growth through brood incubation, but allocating workers to nectar foraging could compromise nest thermoregulation in daytime and produce ‘incubator limitation’.
2. We hypothesise that colonies in nectar-poor habitats experience stronger incubator limitation by diverting workers from incubation to foraging, but this potential effect of habitat quality on colony fitness via task allocation is not fully understood.
3. We therefore modelled levels of nectar foraging in relation to forage richness and theoretically estimated the impact of incubator-limitation on colony fitness. Additionally, we investigated whether live colonies of bumble bees (Bombus terrestris) responded to manipulation of their sugar supply as if incubator-limited.
4. Model solutions for environmentally realistic scenarios showed that colonies allocate up to one third of workers to nectar foraging in order to avoid sugar starvation during sustained incubation. The incubator-limitation that results can strongly reduce colony reproduction, but its impact depends on the temperature regime of the nesting habitat.
5. Live colonies allocated between one sixth and one third of daytime worker effort to foraging and responded to sugar supplementation as if incubator-limited.
6. These findings suggest that forage richness and nest temperature relations could interact to affect the fitness of wild bumble bee colonies through incubator limitation. Our testable theory promises an integrative understanding of how forage quality and climate could govern the distribution and abundance of bumble bees and other eusocial insects that utilise brood incubation by their worker caste.
Abstract.
Schott M, Sandmann M, Cresswell JE, Becher MA, Eichner G, Brandt DT, Halitschke R, Krueger S, Morlock G, Düring RA, et al (2021). Honeybee colonies compensate for pesticide-induced effects on royal jelly composition and brood survival with increased brood production.
Scientific Reports,
11(1).
Abstract:
Honeybee colonies compensate for pesticide-induced effects on royal jelly composition and brood survival with increased brood production
Sublethal doses of pesticides affect individual honeybees, but colony-level effects are less well understood and it is unclear how the two levels integrate. We studied the effect of the neonicotinoid pesticide clothianidin at field realistic concentrations on small colonies. We found that exposure to clothianidin affected worker jelly production of individual workers and created a strong dose-dependent increase in mortality of individual larvae, but strikingly the population size of capped brood remained stable. Thus, hives exhibited short-term resilience. Using a demographic matrix model, we found that the basis of resilience in dosed colonies was a substantive increase in brood initiation rate to compensate for increased brood mortality. However, computer simulation of full size colonies revealed that the increase in brood initiation led to severe reductions in colony reproduction (swarming) and long-term survival. This experiment reveals social regulatory mechanisms on colony-level that enable honeybees to partly compensate for effects on individual level.
Abstract.
2020
Cresswell J (2020). Moderate pollination limitation in some entomophilous crops of Europe: dataset of field-specific measurements.
Abstract:
Moderate pollination limitation in some entomophilous crops of Europe: dataset of field-specific measurements
This spreadsheet displays field-to-field variation in flower density, insect visitation and pollination deficit
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Chatterjee A, Chatterjee S, Smith B, Cresswell JE, Basu P (2020). Predicted thresholds for natural vegetation cover to safeguard pollinator services in agricultural landscapes.
Agriculture, Ecosystems and Environment,
290Abstract:
Predicted thresholds for natural vegetation cover to safeguard pollinator services in agricultural landscapes
The conversion of natural vegetation into cultivated land can cause pollinator declines and thereby degrade pollination services to crops and wildflowers. The effect of landscape composition on pollinator abundance is well established, but its impact on pollination intensity and crop yield is not fully resolved. We therefore studied pollination of two crops in India, brinjal (Solanum melongena) and mustard (Brassica nigra), along a landscape-scale gradient in habitat transformation from forest-dominated natural vegetation to intensive cultivation. We quantified the pollination requirements (pollen receipt-seed set relationships) of the crops and the levels of pollen delivery by their principal pollinators, bees. Combining these with field surveys of pollinator abundance, we modelled the levels of pollination service to fields along the landscape gradient. Projected pollination services declined as the area occupied by natural vegetation decreased. We identified thresholds at which bee pollination no longer supported maximum seed set, which were landscapes with approximately one quarter (27 %) of nearby natural vegetation for brinjal fields and one fifth (18 %) for mustard. Our findings indicate that preserving or restoring the cover of natural habitats above these minimum thresholds could be a valuable strategy for maintaining pollinator abundance and safeguarding yield in these bee-pollinated crops.
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Mulvey J, Cresswell JE (2020). Time-dependent effects on bumble bees of dietary exposures to farmland insecticides (imidacloprid, thiamethoxam and fipronil).
Pest Manag Sci,
76(8), 2846-2853.
Abstract:
Time-dependent effects on bumble bees of dietary exposures to farmland insecticides (imidacloprid, thiamethoxam and fipronil).
BACKGROUND: Farmland bees encounter insecticides in their diet when visiting the flowers of pesticide-treated crops with residues in nectar and pollen. A sustained exposure to even trace residues could be severely harmful if the ingested substance has a long biological half-life and its toxicity therefore intensifies over time, which is termed time-reinforced toxicity (TRT). Bumble bees are important farmland pollinators, but their susceptibility to TRT from insecticides has not been established previously. This study therefore investigated the potential for three farmland insecticides (imidacloprid, thiamethoxam and fipronil) to generate TRT in bumble bees (Bombus terrestris L.) by dietary exposure in the laboratory using lethality as an endpoint under both fixed-dose and pulsed-dose regimes. RESULTS: the insecticides varied in toxic effect. Fipronil exposures produced a dose-dependent reduction in longevity (days of exposure survived) and strong TRT with no evidence of clearance-based recovery. Thiamethoxam exposures also produced a dose-dependent reduction in longevity, but with moderate TRT and evidence of some clearance-based recovery. Imidacloprid exposures produced a hormesis with reduced longevity only at the highest doses and an absence of TRT. CONCLUSION: Our study further confirms the potential for certain dietary insecticides at trace levels to harm farmland bees during sustained exposures because of their capacity to cause time-reinforced toxicity. Our findings suggest that regulatory oversight of pesticides will better safeguard bee health by testing the active ingredients of farmland agrochemicals for their capacity to produce TRT in these ecologically important nontarget organisms. Our study demonstrates the potential for certain dietary insecticides at trace levels to harm farmland bumble bees during sustained exposures because of their capacity to cause time-reinforced toxicity. © 2020 Society of Chemical Industry.
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2019
Mulvey J (2019). Developing a New Testing Paradigm for Risk-Assessment of Bee-Pesticide Interactions – Quantifying the Pace of Neonicotinoid Toxicokinetics.
Abstract:
Developing a New Testing Paradigm for Risk-Assessment of Bee-Pesticide Interactions – Quantifying the Pace of Neonicotinoid Toxicokinetics
Neonicotinoid pesticides, which are used to protect crops from certain pests, have been correlated with the decline of non-target insect species, including bumblebees. However, despite a myriad of studies into the interaction and impact of neonicotinoids, uncertainty remains as to the risks these xenobiotics pose to bees. In particular, the question of bioaccumulation, defined here as how long neonicotinoids persist in the body (i.e. fast or slow toxicokinetics) has not yet been determined for neonicotinoids and bumblebee species. Moreover, while the implications of bioaccumulation on non-target species are severe, regulatory standards continue to rely on acute paradigm testing (e.g. 48-hour LC50s or NOECs) that may inherently fail to capture bioaccumulation.
First, I reviewed the literature on the pace of toxicokinetics for neonicotinoids, found in studies on enzymatic metabolism and receptor site bonding of these substances, which are the main pathways for clearance of xenobiotics. The literature supports that neonicotinoids have face-paced toxicokinetics and are unlikely to bioaccumulate in bees. I further reviewed current regulatory practices (LC50s and NOECs), and how a proxy for bioaccumulation can be derived using dose-dependence studies analysed with Haber’s Law.
Next, I conducted laboratory experiments examining the usefulness of Haber’s Law for quantifying bioaccumulation using the neonicotinoids imidacloprid and thiamethoxam, and the known bioaccumulative phenylpyrazole, fipronil, as a positive control. Here, not only did I corroborate the literature review findings that neonicotinoids likely have face-paced toxicokinetics, I found evidence that fipronil has bioaccumulative properties, which underscores the usefulness of Haber’s Law in regulatory testing for bioaccumulation.
Finally, I used 96-hour pulse-exposures to assess a proxy for toxicokinetic pace. Bees with pulsed exposures should have less injury than constant exposures if pesticides are easily cleared. Again, thiamethoxam and fipronil showed signs of differing toxicokinetic pace. These quantifiers could be used to fill a regulatory gap for bioaccumulation addressing toxicokinetic pace.
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Bartual AM, Sutter L, Bocci G, Moonen AC, Cresswell J, Entling M, Giffard B, Jacot K, Jeanneret P, Holland J, et al (2019). The potential of different semi-natural habitats to sustain pollinators and natural enemies in European agricultural landscapes.
Agriculture, Ecosystems and Environment,
279, 43-52.
Abstract:
The potential of different semi-natural habitats to sustain pollinators and natural enemies in European agricultural landscapes
Semi-natural habitats (SNH) are vital to sustain pollinators and natural enemies, and the ecosystem services they provide in agroecosystems. However, little is known about the relative importance of different SNH types and their vegetation traits for pollinators and natural enemies. Yet, such knowledge is essential for effective habitat management to promote both functional arthropod groups and associated multiple ecosystem services. We quantified vegetation traits and abundances of pollinators (bees) and natural enemies (predatory flies and parasitic wasps) in 217 SNH differing in type (woody or herbaceous) and shape (linear or areal habitats), for edge and interior locations within each SNH patch with respect to adjacent crops, across 62 agricultural landscapes in four European countries. Pollinators and natural enemies responded distinctively to major SNH types and within-habitat location of SNH: abundance of natural enemies (predatory flies and parasitic wasps) was higher along woody habitat edges than herbaceous SNH or the interior of woody habitats. In contrast, bee abundances, especially of honey bees, were generally higher in areal herbaceous compared to woody SNH. Abundances of both wild bees and managed honey bees were lowest for the interior sampling location in areal woody habitats. These findings reflected divergent key vegetation traits driving pollinator and natural enemy abundances across SNH: bee pollinators increased with herbaceous plant cover and were well predicted by SNH type and the floral abundance of identified key plant trait groups. In contrast, floral abundances of these plant groups were poor predictors of the studied natural enemies, which were better predicted by SNH type and sampling location within SNH. Our findings stress the need to move beyond the simplistic pooling of SNH types and highlight the importance of considering their vegetation traits to more reliably predict pollinators and natural enemies in agroecosystems. They suggest that the floral abundance of key groups of flowering plants is crucial for habitat management to promote bee pollinators, while vegetation-structural traits appear more important for predatory flies and parasitoids. The distinct importance of different SNH types and associated vegetation traits for pollinators and natural enemies calls for agroecosystem management ensuring diverse SNH with complementary vegetation traits to concomitantly foster pollination and pest control services.
Abstract.
Livesey JS, Constable C, Rawlinson WG, Robotham AM, Wright C, Hampshire AE, Klark EG, Borrows WA, Horsell D, Cresswell JE, et al (2019). The power and efficiency of brood incubation in queenless microcolonies of bumble bees (Bombus terrestris L.).
Ecological Entomology,
44(5), 601-609.
Abstract:
The power and efficiency of brood incubation in queenless microcolonies of bumble bees (Bombus terrestris L.)
1. Ground-nesting colonies of bumble bees incubate their brood at > 30 °C if floral forage provides sufficient energy and the thermogenic power of the colony can counteract cool soil conditions. To explore the basis of incubation, the thermogenic power and sugar consumption of orphaned nests of bumble bee workers (microcolonies) were investigated under laboratory conditions. 2. This study tested experimentally the effect of variation in worker number (ranging from four to 12 adults) on a microcolony's capacity to regulate brood temperature and recover from acute cold exposure. Microcolonies were provided with ad libitum sugar syrup and minimal insulation and maintained at an ambient temperature of c. 25 °C. Energy conversion efficiency was estimated by comparing sugar consumption with the power required for artificial incubation. The joint energetics of foraging and incubation were modelled in wild colonies to explore the effect of colony size and landscape quality on thermoregulation. 3. The results showed that all sizes of microcolonies regulated brood temperature at c. 31 °C under laboratory conditions, which required 96 mW of thermogenic power. It was estimated that individual workers of B. terrestris generated an incubatory power of 35 mW. The smallest microcolonies had the highest conversion efficiency (57%), apparently because few workers were required for incubation. 4. Modelling indicated that small microcolonies of three to seven adult workers have the capacity for normal brood incubation in the wild, but that the minimum viable colony size increases as floral forage becomes poorer or more distant. 5. These preliminary findings suggest the feasibility of identifying the minimum conditions (forage quality, soil temperature, and colony size) necessary for brood incubation by queenright colonies in the wild.
Abstract.
2018
Hamston TJ, de Vere N, King RA, Pellicer J, Fay MF, Cresswell JE, Stevens JR (2018). Apomixis and hybridization drives reticulate evolution and phyletic differentiation in sorbus l.: Implications for conservation.
Frontiers in Plant Science,
871Abstract:
Apomixis and hybridization drives reticulate evolution and phyletic differentiation in sorbus l.: Implications for conservation
Hybridization and polyploidy are major forces in the evolution of plant diversity and the study of these processes is of particular interest to understand how novel taxa are formed and how they maintain genetic integrity. Sorbus is an example of a genus where active diversification and speciation are ongoing and, as such, represents an ideal model to investigate the roles of hybridization, polyploidy and apomixis in a reticulate evolutionary process. To elucidate breeding systems and evolutionary origins of a complex of closely related Sorbus taxa, we assessed genotypic diversity and population structure within and among taxa, combining data from nuclear DNA microsatellite markers and flow cytometry. Clonal analysis and low genotypic diversity within the polyploid taxa suggest apomixis is obligate. However, genetic variation has led to groups of ‘clone-mates’ within apomictic taxa that strongly suggest mutation is responsible for the genotypic diversity of these apomictic lineages. In addition, microsatellite profiles and site demographics suggest hybridization events among apomictic polyploid Sorbus may have contributed to the extant diversity of recognized taxa in this region. This research demonstrates that both macro- and micro-evolutionary processes are active within this reticulate Sorbus complex. Conservation measures should be aimed at maintaining this process and should therefore be prioritized for those areas of Sorbus species richness where the potential for interspecific gene flow is greatest.
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Pfister SC, Eckerter PW, Krebs J, Cresswell JE, Schirmel J, Entling MH (2018). Dominance of cropland reduces the pollen deposition from bumble bees.
Sci Rep,
8(1).
Abstract:
Dominance of cropland reduces the pollen deposition from bumble bees.
Intensive agricultural landscapes can be hostile for bees due to a lack of floral and nesting resources, and due to management-related stress such as pesticide use and soil tillage. This threatens the pollination services that bees deliver to insect-pollinated crops. We studied the effects of farming intensity (organic vs. conventional, number of insecticide applications) and availability of semi-natural habitats at the field and landscape scale on pollinator visits and pollen delivery to pumpkin in Germany. We found that wild bumble bees were the key pollinators of pumpkin in terms of pollen delivery, despite fivefold higher visitation frequency of honey bees. Critically, we observed that the area of cropland had stronger effects on bees' pollen deposition than the area of seminatural habitats. Specifically, a 10% increase of the proportion of cropland reduced pollen delivery by 7%. Pumpkin provides a striking example for a key role of wild pollinators in crop pollination even at high numerical dominance of honey bees. In addition, our findings suggest that habitat conversion to agricultural land is a driver of deteriorating pollination. This underlines the importance to maintain sufficient areas of non-crop habitats in agricultural landscapes.
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Collison EJ, Hird H, Tyler CR, Cresswell JE (2018). Effects of neonicotinoid exposure on molecular and physiological indicators of honey bee immunocompetence.
Apidologie,
49(2), 196-208.
Abstract:
Effects of neonicotinoid exposure on molecular and physiological indicators of honey bee immunocompetence
Bee declines have been associated with various stressors including pesticides and pathogens. We separately exposed immune-challenged adult worker honey bees (Apis mellifera L.) to two neonicotinoid pesticides, thiamethoxam (10 ppb) and imidacloprid (102 ppb), by dietary delivery. We found that whereas neonicotinoid exposure weakly affected transcriptional responses of antimicrobial genes, it did not detectably affect the physiological antimicrobial response as measured by a lytic clearance assay of haemolymph. Our findings add to the evidence that transcriptional responses in immune-related genes are not yet reliable indicators of pesticide impacts on bee health, which suggests caution in their future use as biomarkers in pesticide risk assessment.
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Holder PJ, Jones A, Tyler CR, Cresswell JE (2018). Fipronil pesticide as a suspect in historical mass mortalities of honey bees.
Proc Natl Acad Sci U S A,
115(51), 13033-13038.
Abstract:
Fipronil pesticide as a suspect in historical mass mortalities of honey bees.
Mass mortalities of honey bees occurred in France in the 1990s coincident with the introduction of two agricultural insecticides, imidacloprid and fipronil. Imidacloprid, a neonicotinoid, was widely blamed, but the differential potency of imidacloprid and fipronil has been unclear because of uncertainty over their capacity to bioaccumulate during sustained exposure to trace dietary residues and, thereby, cause time-reinforced toxicity (TRT). We experimentally quantified the toxicity of fipronil and imidacloprid to honey bees and incorporated the observed mortality rates into a demographic simulation of a honey bee colony in an environmentally realistic scenario. Additionally, we evaluated two bioassays from new international guidance for agrochemical regulation, which aim to detect TRT. Finally, we used analytical chemistry (GC-MS) to test for bioaccumulation of fipronil. We found in demographic simulations that only fipronil produced mass mortality in honey bees. In the bioassays, only fipronil caused TRT. GC-MS analysis revealed that virtually all of the fipronil ingested by a honey bee in a single meal was present 6 d later, which suggests that bioaccumulation is the basis of TRT in sustained dietary exposures. We therefore postulate that fipronil, not imidacloprid, caused the mass mortalities of honey bees in France during the 1990s because it is lethal to honey bees in even trace doses due to its capacity to bioaccumulate and generate TRT. Our results provide evidence that recently proposed laboratory bioassays can discriminate harmful bioaccumulative substances and, thereby, address evident shortcomings in a regulatory system that had formerly approved fipronil for agricultural use.
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Holder PJ, Jones A, Tyler C, Cresswell J (2018). Holder et al (PNAS): Datasets for dietary exposures of mixed-age honey bees to fipronil, imidacloprid, thiamethoxam and cypermethrin.
Abstract:
Holder et al (PNAS): Datasets for dietary exposures of mixed-age honey bees to fipronil, imidacloprid, thiamethoxam and cypermethrin
Feeding and longevity endpoints for laboratory exposures of caged honey bees to various dietary pesticides. Analysis of these data are presented in Holder et al. 2018 (PNAS).
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Raimets R, Karise R, Mänd M, Kaart T, Ponting S, Song J, Cresswell JE (2018). Synergistic interactions between a variety of insecticides and an ergosterol biosynthesis inhibitor fungicide in dietary exposures of bumble bees (Bombus terrestris L.).
Pest Manag Sci,
74(3), 541-546.
Abstract:
Synergistic interactions between a variety of insecticides and an ergosterol biosynthesis inhibitor fungicide in dietary exposures of bumble bees (Bombus terrestris L.).
BACKGROUND: in recent years, concern has been raised over honey bee colony losses, and also among wild bees there is evidence for extinctions and range contractions in Europe and North America. Pesticides have been proposed as a potential cause of this decline. Bees are exposed simultaneously to a variety of agrochemicals, which may cause synergistically detrimental impacts, which are incompletely understood. We investigated the toxicity of the fungicide imazalil in mixture with four common insecticides: fipronil (phenylpyrazoid), cypermethrin (pyrethroid), thiamethoxam, and imidacloprid (neonicotinoids). Ergosterol biosynthesis inhibitor (EBI) fungicides like imazalil can inhibit P450 detoxification systems in insects and therefore fungicide - insecticide co-occurrence might produce synergistic toxicity in bees. We assessed the impact of dietary fungicide - insecticide mixtures on the mortality and feeding rates of laboratory bumble bees (Bombus terrestris L.). RESULTS: Regarding mortality, imazalil synergised the toxicity of fipronil, cypermethrin and thiamethoxam, but not imidacloprid. We found no synergistic effects on feeding rates. CONCLUSION: Our findings suggest that P450-based detoxification processes are differentially important in mitigating the toxicity of certain insecticides, even those of the same chemical class. Our evidence that cocktail effects can arise in bumble bees should extend concern about the potential impacts of agrochemical mixtures to include wild bee species in farmland. © 2017 Society of Chemical Industry.
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Cresswell JE (2018). Three cardinal numbers to safeguard bees against pesticide exposure: LD50, NOEC (revised) and the Haber exponent.
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2017
Cresswell JE (2017). A demographic approach to evaluating the impact of stressors on bumble bee colonies.
Ecological Entomology,
42(2), 221-229.
Abstract:
A demographic approach to evaluating the impact of stressors on bumble bee colonies
1. Natural and anthropogenic stressors threaten the sustainability of bumble bees and evaluating their impact is essential to the stewardship of these valuable pollinators. Demographic modelling provides a framework for testing hypotheses about the impacts of stressors, but it has not previously been applied to bumble bees. 2. I therefore formulated a demographic model for a bumble bee colony and then quantified the impact of two stressors, pesticide exposure and spider predation, by perturbing it with their known effects. 3. By simulating a laboratory exposure of Bombus terrestris L. to dietary imidacloprid (a neonicotinoid insecticide), I tested whether the observed colony decline was explained solely by a toxic effect on the fecundity of the foundress queen. By simulating field observations of B. terricola Kirby, I tested whether predation by crab spiders reduced colony fitness sufficiently to provide an adaptive explanation for avoidance behaviours seen when bumble bees encounter spiders. 4. In B. terrestris, a dose-appropriate decrease in fecundity predicted the observed colony decline, which implicates this as a principal mechanism of toxicity. In B. terricola, doubling the rate of spider predation reduced a colony's production of new queens by 11%, which implies that spider avoidance is highly adaptive. 5. These analyses illustrate the utility of demographic modelling for quantifying the impacts of stressors on bumble bees. In the future, models of this type could be used to investigate a wider range of stressors and to produce thereby knowledge and tools useful for safeguarding bumble bees and the pollination services that they provide.
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Hamston TJ, Wilson RJ, de Vere N, Rich TCG, Stevens JR, Cresswell JE (2017). Breeding system and spatial isolation from congeners strongly constrain seed set in an insect-pollinated apomictic tree: Sorbus subcuneata (Rosaceae).
Sci Rep,
7Abstract:
Breeding system and spatial isolation from congeners strongly constrain seed set in an insect-pollinated apomictic tree: Sorbus subcuneata (Rosaceae).
In plants, apomixis results in the production of clonal offspring via seed and can provide reproductive assurance for isolated individuals. However, many apomicts require pollination to develop functional endosperm for successful seed set (pseudogamy) and therefore risk pollination-limitation, particularly in self-incompatible species that require heterospecific pollen. We used microsatellite paternity analysis and hand pollinations to investigate pollen-limitation in Sorbus subcuneata, a threatened endemic tree that co-occurs with its congener, S. admonitor. We confirmed that S. subcuneata is an obligate pseudogamous apomict, but open-pollinated flowers rarely produced seed (flower-to-seed conversion
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Zou Y, Bianchi FJJA, Jauker F, Xiao H, Chen J, Cresswell J, Luo S, Huang J, Deng X, Hou L, et al (2017). Landscape effects on pollinator communities and pollination services in small-holder agroecosystems.
Agriculture, Ecosystems and Environment,
246, 109-116.
Abstract:
Landscape effects on pollinator communities and pollination services in small-holder agroecosystems
Pollination by insects is key for the productivity of many fruit and non-graminous seed crops, but little is known about the response of pollinators to landscapes dominated by small-holder agriculture. Here we assess the relationships between landscape context, pollinator communities (density and diversity) and pollination of oilseed rape in 18 landscapes with proportions of small-holder farming ranging from 10% to 70% in southern China. To quantify the contribution of pollinators to oilseed rape yield, we manipulated pollinator access in a focal oilseed rape field in each landscape using open and closed cages. The pollinator communities in the focal fields were sampled using pan traps. The abundance of wild pollinators increased significantly with the proportion of cultivated land, but the diversity of the wild pollinator communities declined. The responses of pollinator abundance and diversity to cultivated land were best explained at scales of around 1000 m. The abundance of the unmanaged honey bee Apis cerana was positively associated with the proportion of cultivated land, whereas the abundance of the managed A. mellifera was not. A pollination services index (PSI) was calculated by comparing the reproductive investment in seeds between plants with or without pollinator access. PSI was positively correlated with wild pollinator abundance, but not with the abundance of honeybee species. PSI was also not significantly correlated with the area proportion of cultivated land. Our results indicate that crop dominated landscapes with numerous small fields supported an abundant, but relatively species poor bee community that delivered pollination services to oilseed rape. Conservation of (semi-)natural habitats, however, is important for maintaining the diversity of wild pollinators.
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Cresswell JE (2017). Protocol for evaluating whether a test substance shows bioaccumulative properties using Haber’s Law.
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Protocol for evaluating whether a test substance shows bioaccumulative properties using Haber’s Law
This protocol analyses the data describing mortality of honey bees during a chronic 10-day oral exposure paradigm as specified in the OECD Test Guideline: Honey bee (Apis mellifera L.), Chronic oral toxicity test,10-day feeding test in the laboratory (Kling & Schmitzer 2015).
The protocol tests the relationship between the concentration of the test substance in the honey bees’ diet, denoted C, and the duration of exposure that is required to produce a specified level of injury (mortality) among the exposed bees, or the ‘time-to-effect’, denoted t.
Specifically, the protocol derives a t-vs.-C relationship from the data and determines its slope when plotted on logarithmic axes, which indicates whether the data conform to Haber’s law. The analysis can identify potentially bioaccumulative test substances, because they are not expected to conform to Haber’s law.
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Pfister SC, Eckerter PW, Schirmel J, Cresswell JE, Entling MH (2017). Sensitivity of commercial pumpkin yield to potential decline among different groups of pollinating bees.
R Soc Open Sci,
4(5).
Abstract:
Sensitivity of commercial pumpkin yield to potential decline among different groups of pollinating bees.
The yield of animal-pollinated crops is threatened by bee declines, but its precise sensitivity is poorly known. We therefore determined the yield dependence of Hokkaido pumpkin in Germany on insect pollination by quantifying: (i) the relationship between pollen receipt and fruit set and (ii) the cumulative pollen deposition of each pollinator group. We found that approximately 2500 pollen grains per flower were needed to maximize fruit set. At the measured rates of flower visitation, we estimated that bumblebees (21 visits/flower lifetime, 864 grains/visit) or honeybees (123 visits, 260 grains) could individually achieve maximum crop yield, whereas halictid bees are ineffective (11 visits, 16 grains). The pollinator fauna was capable of delivering 20 times the necessary amount of pollen. We therefore estimate that pumpkin yield was not pollination-limited in our study region and that it is currently fairly resilient to single declines of honeybees or wild bumblebees.
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Cresswell JE (2017). The effect of dietary neonicotinoid pesticides on non-flight thermogenesis in worker bumble bees (Bombus terrestris).
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The effect of dietary neonicotinoid pesticides on non-flight thermogenesis in worker bumble bees (Bombus terrestris)
Datasets for experiments reported in Potts et al journal article published in Joornal of Insect Physiology
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2016
Collison E, Hird H, Cresswell J, Tyler C (2016). Interactive effects of pesticide exposure and pathogen infection on bee health – a critical analysis.
Biological Reviews,
91(4), 1006-1019.
Abstract:
Interactive effects of pesticide exposure and pathogen infection on bee health – a critical analysis
Bees are fundamentally important for pollination services and declines in populations could have significant economic and environmental implications. Pesticide exposure and pathogen infection are recognised as potential stressors impacting upon bee populations and recently there has been a surge in research on pesticide–disease interactions to reflect environmentally realistic scenarios better. We critically analyse the findings on pesticide–disease interactions, including effects on the survival, pathogen loads and immunity of bees, and assess the suitability of various endpoints to inform our mechanistic understanding of these interactions. We show that pesticide exposure and pathogen infection have not yet been found to interact to affect worker survival under field-realistic scenarios. Colony-level implications of pesticide effects on Nosema infections, viral loads and honey bee immunity remain unclear as these effects have been observed in a laboratory setting only using a small range of pesticide exposures, generally exceeding those likely to occur in the natural environment, and assessing a highly selected series of immune-related endpoints. Future research priorities include the need for a better understanding of pesticide effects on the antimicrobial peptide (AMP) component of an individual's immune response and on social defence behaviours. Interactions between pesticide exposure and bacterial and fungal infections have yet to be addressed. The paucity of studies in non-Apis bee species is a further major knowledge gap.
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Gill RJ, Baldock KCR, Brown MJF, Cresswell JE, Dicks LV, Fountain MT, Garratt MPD, Gough LA, Heard MS, Holland JM, et al (2016). Protecting an Ecosystem Service: Approaches to Understanding and Mitigating Threats to Wild Insect Pollinators.
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54, 135-206.
Abstract:
Protecting an Ecosystem Service: Approaches to Understanding and Mitigating Threats to Wild Insect Pollinators
Insect pollination constitutes an ecosystem service of global importance, providing significant economic and aesthetic benefits as well as cultural value to human society, alongside vital ecological processes in terrestrial ecosystems. It is therefore important to understand how insect pollinator populations and communities respond to rapidly changing environments if we are to maintain healthy and effective pollinator services. This chapter considers the importance of conserving pollinator diversity to maintain a suite of functional traits and provide a diverse set of pollinator services. We explore how we can better understand and mitigate the factors that threaten insect pollinator richness, placing our discussion within the context of populations in predominantly agricultural landscapes in addition to urban environments. We highlight a selection of important evidence gaps, with a number of complementary research steps that can be taken to better understand: (i) the stability of pollinator communities in different landscapes in order to provide diverse pollinator services; (ii) how we can study the drivers of population change to mitigate the effects and support stable sources of pollinator services and (iii) how we can manage habitats in complex landscapes to support insect pollinators and provide sustainable pollinator services for the future. We advocate a collaborative effort to gain higher quality abundance data to understand the stability of pollinator populations and predict future trends. In addition, for effective mitigation strategies to be adopted, researchers need to conduct rigorous field testing of outcomes under different landscape settings, acknowledge the needs of end-users when developing research proposals and consider effective methods of knowledge transfer to ensure effective uptake of actions. © 2016 Elsevier Ltd.
Abstract.
Cresswell JE (2016). The impacts of agrochemical pesticides on bees in intensively cultivated farmland. In (Ed) Pollination Services to Agriculture: Sustaining and Enhancing a Key Ecosystem Service, 155-179.
2015
Cresswell J, Goulson D (2015). In response: Current evidence and implications--An academic perspective.
Environ Toxicol Chem,
34(7), 1454-1456.
Author URL.
2014
Cresswell JE, Robert FXL, Florance H, Smirnoff N (2014). Clearance of ingested neonicotinoid pesticide (imidacloprid) in honey bees (Apis mellifera) and bumblebees (Bombus terrestris).
Pest Management Science,
70(2), 332-337.
Abstract:
Clearance of ingested neonicotinoid pesticide (imidacloprid) in honey bees (Apis mellifera) and bumblebees (Bombus terrestris)
BACKGROUND: Bees in agricultural landscapes are exposed to dietary pesticides such as imidacloprid when they feed from treated mass-flowering crops. Concern about the consequent impact on bees makes it important to understand their resilience. In the laboratory, the authors therefore fed adult worker bees on dosed syrup (125 μg L. of imidacloprid, or 98 μg kg ) either continuously or as a pulsed exposure and measured their behaviour (feeding and locomotory activity) and whole-body residues. RESULTS: on dosed syrup, honey bees maintained much lower bodily levels of imidacloprid than bumblebees (
Abstract.
Full text.
Cresswell JE, Robert F-XL, Florance H, Smirnoff N (2014). Clearance of ingested neonicotinoid pesticide (imidacloprid) in honey bees (Apis mellifera) and bumblebees (Bombus terrestris).
Pest Manag Sci,
70(2), 332-337.
Abstract:
Clearance of ingested neonicotinoid pesticide (imidacloprid) in honey bees (Apis mellifera) and bumblebees (Bombus terrestris).
BACKGROUND: Bees in agricultural landscapes are exposed to dietary pesticides such as imidacloprid when they feed from treated mass-flowering crops. Concern about the consequent impact on bees makes it important to understand their resilience. In the laboratory, the authors therefore fed adult worker bees on dosed syrup (125 μg L(-1) of imidacloprid, or 98 μg kg(-1)) either continuously or as a pulsed exposure and measured their behaviour (feeding and locomotory activity) and whole-body residues. RESULTS: on dosed syrup, honey bees maintained much lower bodily levels of imidacloprid than bumblebees (
Abstract.
Author URL.
Laycock I, Cotterell KC, O'Shea-Wheller TA, Cresswell JE (2014). Effects of the neonicotinoid pesticide thiamethoxam at field-realistic levels on microcolonies of Bombus terrestris worker bumble bees.
Ecotoxicology and Environmental Safety,
100(1), 153-158.
Abstract:
Effects of the neonicotinoid pesticide thiamethoxam at field-realistic levels on microcolonies of Bombus terrestris worker bumble bees
Neonicotinoid pesticides are currently implicated in the decline of wild bee populations. Bumble bees, Bombus spp. are important wild pollinators that are detrimentally affected by ingestion of neonicotinoid residues. To date, imidacloprid has been the major focus of study into the effects of neonicotinoids on bumble bee health, but wild populations are increasingly exposed to alternative neonicotinoids such as thiamethoxam. To investigate whether environmentally realistic levels of thiamethoxam affect bumble bee performance over a realistic exposure period, we exposed queenless microcolonies of Bombus terrestris L. workers to a wide range of dosages up to 98μgkg. in dietary syrup for 17 days. Results showed that bumble bee workers survived fewer days when presented with syrup dosed at 98μg thiamethoxamkg , while production of brood (eggs and larvae) and consumption of syrup and pollen in microcolonies were significantly reduced by thiamethoxam only at the two highest concentrations (39, 98μgkg ). In contrast, we found no detectable effect of thiamethoxam at levels typically found in the nectars of treated crops (between 1 and 11μgkg ). By comparison with published data, we demonstrate that during an exposure to field-realistic concentrations lasting approximately two weeks, brood production in worker bumble bees is more sensitive to imidacloprid than thiamethoxam. We speculate that differential sensitivity arises because imidacloprid produces a stronger repression of feeding in bumble bees than thiamethoxam, which imposes a greater nutrient limitation on production of brood. © 2013 Elsevier Inc. -1 -1 -1 -1
Abstract.
Laycock I, Cotterell KC, O'Shea-Wheller TA, Cresswell JE (2014). Effects of the neonicotinoid pesticide thiamethoxam at field-realistic levels on microcolonies of Bombus terrestris worker bumble bees.
Ecotoxicol Environ Saf,
100, 153-158.
Abstract:
Effects of the neonicotinoid pesticide thiamethoxam at field-realistic levels on microcolonies of Bombus terrestris worker bumble bees.
Neonicotinoid pesticides are currently implicated in the decline of wild bee populations. Bumble bees, Bombus spp. are important wild pollinators that are detrimentally affected by ingestion of neonicotinoid residues. To date, imidacloprid has been the major focus of study into the effects of neonicotinoids on bumble bee health, but wild populations are increasingly exposed to alternative neonicotinoids such as thiamethoxam. To investigate whether environmentally realistic levels of thiamethoxam affect bumble bee performance over a realistic exposure period, we exposed queenless microcolonies of Bombus terrestris L. workers to a wide range of dosages up to 98 μgkg(-1) in dietary syrup for 17 days. Results showed that bumble bee workers survived fewer days when presented with syrup dosed at 98 μg thiamethoxamkg(-1), while production of brood (eggs and larvae) and consumption of syrup and pollen in microcolonies were significantly reduced by thiamethoxam only at the two highest concentrations (39, 98 μgkg(-1)). In contrast, we found no detectable effect of thiamethoxam at levels typically found in the nectars of treated crops (between 1 and 11 μgkg(-1)). By comparison with published data, we demonstrate that during an exposure to field-realistic concentrations lasting approximately two weeks, brood production in worker bumble bees is more sensitive to imidacloprid than thiamethoxam. We speculate that differential sensitivity arises because imidacloprid produces a stronger repression of feeding in bumble bees than thiamethoxam, which imposes a greater nutrient limitation on production of brood.
Abstract.
Author URL.
Cresswell J (2014). On the natural history of neonicotinoids and bees. Functional Ecology, 28(6), 1311-1312.
2013
Dicks LV, Abrahams A, Atkinson J, Biesmeijer J, Bourn N, Brown C, Brown MJF, Carvell C, Connolly C, Cresswell JE, et al (2013). Identifying key knowledge needs for evidence-based conservation of wild insect pollinators: a collaborative cross-sectoral exercise.
Insect Conservation and Diversity,
6(3), 435-446.
Abstract:
Identifying key knowledge needs for evidence-based conservation of wild insect pollinators: a collaborative cross-sectoral exercise
In response to evidence of insect pollinator declines, organisations in many sectors, including the food and farming industry, are investing in pollinator conservation. They are keen to ensure that their efforts use the best available science. We convened a group of 32 'conservation practitioners' with an active interest in pollinators and 16 insect pollinator scientists. The conservation practitioners include representatives from UK industry (including retail), environmental non-government organisations and nature conservation agencies. We collaboratively developed a long list of 246 knowledge needs relating to conservation of wild insect pollinators in the UK. We refined and selected the most important knowledge needs, through a three-stage process of voting and scoring, including discussions of each need at a workshop. We present the top 35 knowledge needs as scored by conservation practitioners or scientists. We find general agreement in priorities identified by these two groups. The priority knowledge needs will structure ongoing work to make science accessible to practitioners, and help to guide future science policy and funding. Understanding the economic benefits of crop pollination, basic pollinator ecology and impacts of pesticides on wild pollinators emerge strongly as priorities, as well as a need to monitor floral resources in the landscape. © 2012 the Royal Entomological Society.
Abstract.
Laycock I, Cresswell JE (2013). Repression and recuperation of brood production in Bombus terrestris bumble bees exposed to a pulse of the neonicotinoid pesticide imidacloprid.
PLoS One,
8(11).
Abstract:
Repression and recuperation of brood production in Bombus terrestris bumble bees exposed to a pulse of the neonicotinoid pesticide imidacloprid.
Currently, there is concern about declining bee populations and some blame the residues of neonicotinoid pesticides in the nectar and pollen of treated crops. Bumble bees are important wild pollinators that are widely exposed to dietary neonicotinoids by foraging in agricultural environments. In the laboratory, we tested the effect of a pulsed exposure (14 days 'on dose' followed by 14 days 'off dose') to a common neonicotinoid, imidacloprid, on the amount of brood (number of eggs and larvae) produced by Bombus terrestris L. bumble bees in small, standardised experimental colonies (a queen and four adult workers). During the initial 'on dose' period we observed a dose-dependent repression of brood production in colonies, with productivity decreasing as dosage increased up to 98 µg kg(-1) dietary imidacloprid. During the following 'off dose' period, colonies showed a dose-dependent recuperation such that total brood production during the 28-day pulsed exposure was not correlated with imidacloprid up to 98 µg kg(-1). Our findings raise further concern about the threat to wild bumble bees from neonicotinoids, but they also indicate some resilience to a pulsed exposure, such as that arising from the transient bloom of a treated mass-flowering crop.
Abstract.
Author URL.
Van Engelsdorp D, Lengerich E, Spleen A, Dainat B, Cresswell J, Baylis K, Nguyen BK, Soroker V, Underwood R, Human H, et al (2013). Standard epidemiological methods to understand and improve Apis mellifera health.
Journal of Apicultural Research,
52(4).
Abstract:
Standard epidemiological methods to understand and improve Apis mellifera health
In this paper, we describe the use of epidemiological methods to understand and reduce honey bee morbidity and mortality. Essential terms are presented and defined and we also give examples for their use. Defining such terms as disease, population, sensitivity, and specificity, provides a framework for epidemiological comparisons. The term population, in particular, is quite complex for an organism like the honey bee because one can view "epidemiological unit" as individual bees, colonies, apiaries, or operations. The population of interest must, therefore, be clearly defined. Equations and explanations of how to calculate measures of disease rates in a population are provided. There are two types of study design; observational and experimental. The advantages and limitations of both are discussed. Approaches to calculate and interpret results are detailed. Methods for calculating epidemiological measures such as detection of rare events, associating exposure and disease (Odds Ratio and Relative Risk), and comparing prevalence and incidence are discussed. Naturally, for beekeepers, the adoption of any management system must have economic advantage. We present a means to determine the cost and benefit of the treatment in order determine its net benefit. Lastly, this paper presents a discussion of the use of Hill's criteria for inferring causal relationships. This framework for judging cause-effect relationships supports a repeatable and quantitative evaluation process at the population or landscape level. Hill's criteria disaggregate the different kinds of evidence, allowing the scientist to consider each type of evidence individually and objectively, using a quantitative scoring method for drawing conclusions. It is hoped that the epidemiological approach will be more broadly used to study and negate honey bee disease. © IBRA 2013.
Abstract.
Van Engelsdorp D, Lengerich E, Spleen A, Dainat B, Cresswell J, Baylis K, Nguyen BK, Soroker V, Underwood R, Human H, et al (2013). Standard epidemiological methods to understand and improve Apis mellifera health.
Journal of Apicultural Research,
52(1).
Abstract:
Standard epidemiological methods to understand and improve Apis mellifera health
In this paper, we describe the use of epidemiological methods to understand and reduce honey bee morbidity and mortality. Essential terms are presented and defined and we also give examples for their use. Defining such terms as disease, population, sensitivity, and specificity, provides a framework for epidemiological comparisons. The term population, in particular, is quite complex for an organism like the honey bee because one can view "epidemiological unit" as individual bees, colonies, apiaries, or operations. The population of interest must, therefore, be clearly defined. Equations and explanations of how to calculate measures of disease rates in a population are provided. There are two types of study design; observational and experimental. The advantages and limitations of both are discussed. Approaches to calculate and interpret results are detailed. Methods for calculating epidemiological measures such as detection of rare events, associating exposure and disease (Odds Ratio and Relative Risk), and comparing prevalence and incidence are discussed. Naturally, for beekeepers, the adoption of any management system must have economic advantage. We present a means to determine the cost and benefit of the treatment in order determine its net benefit. Lastly, this paper presents a discussion of the use of Hill's criteria for inferring causal relationships. This framework for judging cause-effect relationships supports a repeatable and quantitative evaluation process at the population or landscape level. Hill's criteria disaggregate the different kinds of evidence, allowing the scientist to consider each type of evidence individually and objectively, using a quantitative scoring method for drawing conclusions. It is hoped that the epidemiological approach will be more broadly used to study and negate honey bee disease. Copyright © IBRA 2013.
Abstract.
2012
Cresswell JE, Thompson HM (2012). Comment on "A common pesticide decreases foraging success and survival in honey bees".
Science,
337(6101).
Abstract:
Comment on "A common pesticide decreases foraging success and survival in honey bees".
Henry et al. (Reports, 20 April, p. 348) used a model to predict that colony collapse in honey bees could be precipitated by pesticide-induced intoxication that disrupts navigation. Here, we show that collapse disappears when the model is recalculated with parameter values appropriate to the season when most pesticide-treated flowering crops bloom.
Abstract.
Author URL.
Cresswell JE, Desneux N, vanEngelsdorp D (2012). Dietary traces of neonicotinoid pesticides as a cause of population declines in honey bees: an evaluation by Hill's epidemiological criteria.
Pest Management Science,
68(6), 819-827.
Abstract:
Dietary traces of neonicotinoid pesticides as a cause of population declines in honey bees: an evaluation by Hill's epidemiological criteria
Background: Honey bees are important pollinators of both crops and wild plants. Pesticide regimes that threaten their sustainability should therefore be assessed. As an example, evidence that the agricultural use of neonicotinoid pesticides is a cause of the recently observed declines in honey bees is examined. The aim is to define exacting demographic conditions for a detrimental factor to precipitate a population decline, and Hill's epidemiological 'causality criteria' are employed as a structured process for making an expert judgement about the proposition that trace dietary neonicotinoids in nectar and pollen cause population declines in honey bees. Results: in spite of the absence of decisive experimental results, the analysis shows that, while the proposition is a substantially justified conjecture in the context of current knowledge, it is also substantially contraindicated by a wide variety of circumstantial epidemiological evidence. Conclusion:It is concluded that dietary neonicotinoids cannot be implicated in honey bee declines, but this position is provisional because important gaps remain in current knowledge. Avenues for further investigations to resolve this longstanding uncertainty are therefore identified. © 2012 Society of Chemical Industry.
Abstract.
Cresswell JE, Desneux N, vanEngelsdorp D (2012). Dietary traces of neonicotinoid pesticides as a cause of population declines in honey bees: an evaluation by Hill's epidemiological criteria.
Pest Manag Sci,
68(6), 819-827.
Abstract:
Dietary traces of neonicotinoid pesticides as a cause of population declines in honey bees: an evaluation by Hill's epidemiological criteria.
BACKGROUND: Honey bees are important pollinators of both crops and wild plants. Pesticide regimes that threaten their sustainability should therefore be assessed. As an example, evidence that the agricultural use of neonicotinoid pesticides is a cause of the recently observed declines in honey bees is examined. The aim is to define exacting demographic conditions for a detrimental factor to precipitate a population decline, and Hill's epidemiological 'causality criteria' are employed as a structured process for making an expert judgement about the proposition that trace dietary neonicotinoids in nectar and pollen cause population declines in honey bees. RESULTS: in spite of the absence of decisive experimental results, the analysis shows that, while the proposition is a substantially justified conjecture in the context of current knowledge, it is also substantially contraindicated by a wide variety of circumstantial epidemiological evidence. CONCLUSION: it is concluded that dietary neonicotinoids cannot be implicated in honey bee declines, but this position is provisional because important gaps remain in current knowledge. Avenues for further investigations to resolve this longstanding uncertainty are therefore identified.
Abstract.
Author URL.
Cresswell JE, Page CJ, Uygun MB, Holmbergh M, Li Y, Wheeler JG, Laycock I, Pook CJ, de Ibarra NH, Smirnoff N, et al (2012). Differential sensitivity of honey bees and bumble bees to a dietary insecticide (imidacloprid). Zoology
Cresswell JE, Page CJ, Uygun MB, Holmbergh M, Li Y, Wheeler JG, Laycock I, Pook CJ, de Ibarra NH, Smirnoff N, et al (2012). Differential sensitivity of honey bees and bumble bees to a dietary insecticide (imidacloprid).
Zoology,
115(6), 365-371.
Abstract:
Differential sensitivity of honey bees and bumble bees to a dietary insecticide (imidacloprid)
Currently, there is concern about declining bee populations and the sustainability of pollination services. One potential threat to bees is the unintended impact of systemic insecticides, which are ingested by bees in the nectar and pollen from flowers of treated crops. To establish whether imidacloprid, a systemic neonicotinoid and insect neurotoxin, harms individual bees when ingested at environmentally realistic levels, we exposed adult worker bumble bees, Bombus terrestris L. (Hymenoptera: Apidae), and honey bees, Apis mellifera L. (Hymenoptera: Apidae), to dietary imidacloprid in feeder syrup at dosages between 0.08 and 125μgl. Honey bees showed no response to dietary imidacloprid on any variable that we measured (feeding, locomotion and longevity). In contrast, bumble bees progressively developed over time a dose-dependent reduction in feeding rate with declines of 10-30% in the environmentally relevant range of up to 10μgl , but neither their locomotory activity nor longevity varied with diet. To explain their differential sensitivity, we speculate that honey bees are better pre-adapted than bumble bees to feed on nectars containing synthetic alkaloids, such as imidacloprid, by virtue of their ancestral adaptation to tropical nectars in which natural alkaloids are prevalent. We emphasise that our study does not suggest that honey bee colonies are invulnerable to dietary imidacloprid under field conditions, but our findings do raise new concern about the impact of agricultural neonicotinoids on wild bumble bee populations. © 2012 Elsevier GmbH. -1 -1
Abstract.
Laycock I, Lenthall KM, Barratt AT, Cresswell JE (2012). Effects of imidacloprid, a neonicotinoid pesticide, on reproduction in worker bumble bees (Bombus terrestris).
Ecotoxicology,
21(7), 1937-1945.
Abstract:
Effects of imidacloprid, a neonicotinoid pesticide, on reproduction in worker bumble bees (Bombus terrestris)
Bumble bees are important pollinators whose populations have declined over recent years, raising widespread concern. One conspicuous threat to bumble bees is their unintended exposure to trace residues of systemic neonicotinoid pesticides, such as imidacloprid, which are ingested when bees forage on the nectar and pollen of treated crops. However, the demographic consequences for bumble bees of exposure to dietary neonicotinoids have yet to be fully established. To determine whether environmentally realistic levels of imidacloprid are capable of making a demographic impact on bumble bees, we exposed queenless microcolonies of worker bumble bees, Bombus terrestris, to a range of dosages of dietary imidacloprid between zero and 125 μg L. and examined the effects on ovary development and fecundity. Microcolonies showed a dose-dependent decline in fecundity, with environmentally realistic dosages in the range of 1 lg L-1 capable of reducing brood production by one third. In contrast, ovary development was unimpaired by dietary imidacloprid except at the highest dosage. Imidacloprid reduced feeding on both syrup and pollen but, after controlling statistically for dosage, microcolonies that consumed more syrup and pollen produced more brood. We therefore speculate that the detrimental effects of imidacloprid on fecundity emerge principally from nutrient limitation imposed by the failure of individuals to feed. Our findings raise concern about the impact of neonicotinoids on wild bumble bee populations. However, we recognize that to fully evaluate impacts on wild colonies it will be necessary to establish the effect of dietary neonicotinoids on the fecundity of bumble bee queens. © Springer Science+Business Media, LLC 2012. -1
Abstract.
Laycock I, Lenthall KM, Barratt AT, Cresswell JE (2012). Effects of imidacloprid, a neonicotinoid pesticide, on reproduction in worker bumble bees (Bombus terrestris).
Ecotoxicology,
21(7), 1937-1945.
Abstract:
Effects of imidacloprid, a neonicotinoid pesticide, on reproduction in worker bumble bees (Bombus terrestris).
Bumble bees are important pollinators whose populations have declined over recent years, raising widespread concern. One conspicuous threat to bumble bees is their unintended exposure to trace residues of systemic neonicotinoid pesticides, such as imidacloprid, which are ingested when bees forage on the nectar and pollen of treated crops. However, the demographic consequences for bumble bees of exposure to dietary neonicotinoids have yet to be fully established. To determine whether environmentally realistic levels of imidacloprid are capable of making a demographic impact on bumble bees, we exposed queenless microcolonies of worker bumble bees, Bombus terrestris, to a range of dosages of dietary imidacloprid between zero and 125 μg L(-1) and examined the effects on ovary development and fecundity. Microcolonies showed a dose-dependent decline in fecundity, with environmentally realistic dosages in the range of 1 μg L(-1) capable of reducing brood production by one third. In contrast, ovary development was unimpaired by dietary imidacloprid except at the highest dosage. Imidacloprid reduced feeding on both syrup and pollen but, after controlling statistically for dosage, microcolonies that consumed more syrup and pollen produced more brood. We therefore speculate that the detrimental effects of imidacloprid on fecundity emerge principally from nutrient limitation imposed by the failure of individuals to feed. Our findings raise concern about the impact of neonicotinoids on wild bumble bee populations. However, we recognize that to fully evaluate impacts on wild colonies it will be necessary to establish the effect of dietary neonicotinoids on the fecundity of bumble bee queens.
Abstract.
Author URL.
Laycock I, Lenthall KM, Barratt AT, Cresswell JE (2012). Erratum to: Effects of imidacloprid, a neonicotinoid pesticide, on reproduction in worker bumble bees (Bombus terrestris). Ecotoxicology, 21(7).
Dicks LV, Abrahams A, Atkinson J, Biesmeijer J, Bourn N, Brown C, Brown MJ, Carvell C, Connolly C, Cresswell JE, et al (2012). Identifying key knowledge needs for evidence-based conservation of wild insect pollinators: a collaborative cross-sectoral exercise. Insect Conservation and Diversity
Cresswell JE, Laycock I (2012). Towards the comparative ecotoxicology of bees: the response-response relationship.
Author URL.
2011
Cresswell JE (2011). A meta-analysis of experiments testing the effects of a neonicotinoid insecticide (imidacloprid) on honey bees.
Ecotoxicology,
20(1), 149-157.
Abstract:
A meta-analysis of experiments testing the effects of a neonicotinoid insecticide (imidacloprid) on honey bees.
Honey bees provide important pollination services to crops and wild plants. The agricultural use of systemic insecticides, such as neonicotinoids, may harm bees through their presence in pollen and nectar, which bees consume. Many studies have tested the effects on honey bees of imidacloprid, a neonicotinoid, but a clear picture of the risk it poses to bees has not previously emerged, because investigations are methodologically varied and inconsistent in outcome. In a meta-analysis of fourteen published studies of the effects of imidacloprid on honey bees under laboratory and semi-field conditions that comprised measurements on 7073 adult individuals and 36 colonies, fitted dose-response relationships estimate that trace dietary imidacloprid at field-realistic levels in nectar will have no lethal effects, but will reduce expected performance in honey bees by between 6 and 20%. Statistical power analysis showed that published field trials that have reported no effects on honey bees from neonicotinoids were incapable of detecting these predicted sublethal effects with conventionally accepted levels of certainty. These findings raise renewed concern about the impact on honey bees of dietary imidacloprid, but because questions remain over the environmental relevance of predominantly laboratory-based results, I identify targets for research and provide procedural recommendations for future studies.
Abstract.
Author URL.
2010
Cresswell JE (2010). A mechanistic model of pollinator-mediated gene flow in agricultural safflower.
BASIC AND APPLIED ECOLOGY,
11(5), 415-421.
Author URL.
Full text.
Cresswell JE, Krick J, Patrick MA, Lahoubi M (2010). The aerodynamics and efficiency of wind pollination in grasses.
FUNCTIONAL ECOLOGY,
24(4), 706-713.
Author URL.
Full text.
Cresswell JE (2010). Theoretical analyses of the impact of change in the composition of the pollinator fauna on a pollination system. Applied Entomology and Zoology, 45, 13-20.
2009
Hoyle M, Cresswell JE (2009). Maximum feasible distance of windborne cross-pollination in Brassica napus: a 'mass budget' model.
Ecological Modelling,
220(8), 1090-1097.
Abstract:
Maximum feasible distance of windborne cross-pollination in Brassica napus: a 'mass budget' model
A theory of gene dispersal by wind pollination can make an important contribution to understanding the viability and evolution of important plant groups in the Earth's changing landscape and it can be applied to evaluate concerns about the spread of engineered genes from genetically modified (GM) crops into conventional varieties via windborne pollen. Here, we present a model of cross-pollination between plant populations due to the wind. We perform a 'mass budget' of pollen by accounting for the number of pollen grains from release in the source population, dispersal from the source to the sink population by the wind, and deposition on receptive surfaces in the sink population. Our model can be parameterised for any wind-pollinated species, but we apply it to Brassica napus (oilseed rape or canola) to investigate the threat posed by wind pollination to GM confinement in agriculture. Specifically, we calculate the maximum feasible distance at which a particular level of windborne gene dispersal could be attained. This is equivalent to the separation distance between populations or fields required to achieve a given threshold of gene dispersal or adventitious GM presence. As required, model predictions of the upper bounds on levels of wind-mediated gene dispersal exceed observations from a wide range of published studies. For a level of gene dispersal below 0.9%, which is the EU threshold for GM adventitious presence, we predict that the maximum feasible distance for agricultural fields of B. napus is 1000 m, regardless of field shape and direction of prevailing winds. For fields closer than 1000 m, our model results do not necessarily imply that the 0.9% threshold is likely to be breached, because in this instance we have conservatively set the values of parameters where current knowledge is limited. We also predict that gene dispersal is reduced by 50% when the lag in peak flowering between the source and sink populations is 13 days, and reduced by 90% when the lag is 24 days. We identify further measurements necessary to improve the accuracy of the model predictions. Our model is valuable because it identifies the maximum feasible distance at which a particular level of windborne gene dispersal could be attained, which provides a high-confidence separation distance for a given level of gene containment. © 2009 Elsevier B.V. All rights reserved.
Abstract.
Sebire M, Scott AP, Tyler CR, Cresswell J, Hodgson DJ, Morris S, Sanders MB, Stebbing PD, Katsiadaki I (2009). The organophosphorous pesticide, fenitrothion, acts as an anti-androgen and alters reproductive behavior of the male three-spined stickleback, Gasterosteus aculeatus.
Ecotoxicology,
18(1), 122-133.
Abstract:
The organophosphorous pesticide, fenitrothion, acts as an anti-androgen and alters reproductive behavior of the male three-spined stickleback, Gasterosteus aculeatus.
Fenitrothion (FN) is a widely used organophosphorous pesticide that has structural similarities with the clinical anti-androgen flutamide. The potential for FN to act as an anti-androgen (at exposures of 1, 50, and 200 microg FN/l over a 26-day period) was assessed in male three-spined sticklebacks, Gasterosteus aculeatus, by measuring kidney spiggin concentration, nest-building, and courtship behavior. Spiggin is the glue protein that male sticklebacks use to build their nests and is directly controlled by androgens. FN exposure significantly reduced spiggin production as well as nest-building activity. It also adversely affected courtship--especially the 'zigzag dance' and biting behavior of the males. FN thus appears to have anti-androgenic effects on both the physiology and behavior of the male stickleback.
Abstract.
Author URL.
2008
Cresswell JE (2008). Estimating the Potential for Bee-Mediated Gene Flow in Genetically Modified Crops. In (Ed)
Bee Pollination in Agricultural Ecosystems.
Abstract:
Estimating the Potential for Bee-Mediated Gene Flow in Genetically Modified Crops
Abstract.
2007
Hoyle M, Cresswell JE (2007). A model of patch-to-patch forager movement with application to pollen-mediated gene flow. Journal of Theoretical Biology, 248, 154-163.
Hoyle M, Cresswell JE (2007). A search theory model of patch-to-patch forager movement with application to pollinator-mediated gene flow.
J Theor Biol,
248(1), 154-163.
Abstract:
A search theory model of patch-to-patch forager movement with application to pollinator-mediated gene flow.
We present a spatially implicit analytical model of forager movement, designed to address a simple scenario common in nature. We assume minimal depression of patch resources, and discrete foraging bouts, during which foragers fill to capacity. The model is particularly suitable for foragers that search systematically, foragers that deplete resources in a patch only incrementally, and for sit-and-wait foragers, where harvesting does not affect the rate of arrival of forage. Drawing on the theory of job search from microeconomics, we estimate the expected number of patches visited as a function of just two variables: the coefficient of variation of the rate of energy gain among patches, and the ratio of the expected time exploiting a randomly chosen patch and the expected time travelling between patches. We then consider the forager as a pollinator and apply our model to estimate gene flow. Under model assumptions, an upper bound for animal-mediated gene flow between natural plant populations is approximately proportional to the probability that the animal rejects a plant population. In addition, an upper bound for animal-mediated gene flow in any animal-pollinated agricultural crop from a genetically modified (GM) to a non-GM field is approximately proportional to the proportion of fields that are GM and the probability that the animal rejects a field.
Abstract.
Author URL.
Cresswell JE, Henning K, Pennel C, Lahoubi M, Patrick MA, Young PG, Tabor GR (2007). Conifer ovulate cones accumulate pollen principally by simple impaction.
Proceedings of the National Academy of Sciences of the United States of America,
104(46), 18141-18144.
Abstract:
Conifer ovulate cones accumulate pollen principally by simple impaction
In many pine species (Family Pinaceae), ovulate cones structurally resemble a turbine, which has been widely interpreted as an adaptation for improving pollination by producing complex aerodynamic effects. We tested the turbine interpretation by quantifying patterns of pollen accumulation on ovulate cones in a wind tunnel and by using simulation models based on computational fluid dynamics. We used computer-aided design and computed tomography to create computational fluid dynamics model cones. We studied three species: Pinus radiata, Pinus sylvestris, and Cedrus libani. Irrespective of the approach or species studied, we found no evidence that turbine-like aerodynamics made a significant contribution to pollen accumulation, which instead occurred primarily by simple impaction. Consequently, we suggest alternative adaptive interpretations for the structure of ovulate cones. © 2007 by the National Academy of Sciences of the USA.
Abstract.
Cresswell JE, Henning K, Tabor GR, Young PG (2007). Conifer ovulate cones accumulate pollen principally by simple impaction. Proceedings of the National Academy of Sciences, 104(46), 18141-18144.
Hoyle M, Hayter K, Cresswell JE (2007). Effect of pollinator abundance on self-fertilization and gene flow: Application to GM canola.
Ecological Applications,
17(7), 2123-2135.
Abstract:
Effect of pollinator abundance on self-fertilization and gene flow: Application to GM canola
Cross-pollination from fields of transgenic crops is of great public concern. Although cross-pollination in commercial canola (Brassica napus) fields has been empirically measured, field trials are expensive and do not identify the causes of cross-pollination. Therefore, theoretical models can be valuable because they can provide estimates of cross-pollination at any given site and time. We present a general analytical model of field-to-field gene flow due to the following competing mechanisms: the wind, bees, and autonomous pollination. We parameterize the model for the particular case of field-to-field cross-pollination of genetically modified (GM) canola via the wind and via bumble bees (Bombus spp.) and honey bees (Apis mellifera). We make extensive use of the large data set of bee densities collected during the recent U.K. Farm Scale Evaluations. We predict that canola approaches almost full seed set without pollinators and that autonomous pollination is responsible for ≥25% of seed set, irrespective of pollinator abundance. We do not predict the relative contribution of bees vs. the wind in landscape-scale gene flow in canola. However, under model assumptions, we predict that the maximum field-to-field gene flow due to bumble bees is 0.04% and 0.13% below the current EU limit for adventitious GM presence for winter- and spring-sown canola, respectively. We predict that gene flow due to bees is ∼3.1 times higher at 20% compared to 100% male-fertility, and due to the wind, 1.3 times higher at 20% compared to 100% male-fertility, for both winter- and spring-sown canola. Bumble bee-mediated gene flow is ∼2.7 times higher and wind-mediated gene flow ∼1.7 times lower in spring-sown than in winter-sown canola, regardless of the degree of male-sterility. The model of cross-pollination due to the wind most closely predicted three previously published observations: field-to-field gene flow is low; gene flow increases with the proportion of plants that are male-sterile; and gene flow is higher in winter- than in spring-sown canola. Our results therefore suggest that the wind, not bees, is the main vector of long-distance gene flow in canola. © 2007 by the Ecological Society of America.
Abstract.
Cresswell, J.E. (2007). Estimating the potential for bee-mediated gene flow in genetically-modified (GM) crops. In James RR, Pitts-Singer TL (Eds.) Bees in Agricultural Ecosystems, Oxford University Press.
Cresswell JE, Hoyle M (2007). The effect of wind direction on cross-pollination in wind-pollinated GM crops. Ecological Applications, 17(4), 1234-1243.
2006
Cresswell JE, Hoyle M (2006). A mathematical method for estimating patterns of flower-to-flower gene dispersal from a simple field experiment.
FUNCTIONAL ECOLOGY,
20(2), 245-251.
Author URL.
Cresswell, J.E. (2006). Models of pollinator-mediated gene dispersal in plants. In Harder LD, Barrett SCH (Eds.) Ecology and evolution of flowers, Oxford University Press, 179-219.
Cresswell, J.E. (2006). Remobilization of initially deposited pollen grains has negligible impact on gene dispersal in bumble bee-pollinated Brassica napus. Functional Ecology, 20, 958-965.
Cresswell, J.E. (2006). The influence of pollinator abundance on the dynamics and efficiency of pollination in arable Brassica napus: implications for landscape-scale gene dispersal. Journal of Applied Ecology, 43, 1196-1202.
2005
Cresswell, J.E. (2005). Accurate theoretical prediction of pollinator-mediated gene dispersal. Ecology, 86(3), 574-578.
Davies, T.W. Patrick, M.A.F. Cresswell JE (2005). The aerodynamics of wind pollination in a zoophilous flower. Functional Ecology, 18, 861-866.
Cresswell, J.E. Macnair, M.R. (2005). The potential for adaptive evolution of pollen grain size in Mimulus guttatus. New Phytologist, 167, 289-296.
2004
Cresswell JE, Davies TW, Patrick MA, Russell F, Pennel C, Vicot M, Lahoubi M (2004). Aerodynamics of wind pollination in a zoophilous flower, Brassica napus.
Functional Ecology,
18(6), 861-866.
Abstract:
Aerodynamics of wind pollination in a zoophilous flower, Brassica napus
1. The flower of Brassica napus L. appears to be typically zoophilous (suited to animal pollination) because of its visually attractive petals, robust stigma and nectaries. Pollination by wind is feasible, however, and its likely effectiveness is not immediately foreseeable because of the complexity of interactions between objects and windborne particles. 2. Computational fluid dynamics (CFD) and wind-tunnel experiments were used to investigate the aerodynamic interactions between the flower and a windborne suspension of its pollen. 3. The flower's petals handicapped wind pollination by reducing the target efficiency of the upwind-facing stigrna. For downwind-facing flowers, pollen reception was negligible. 4. Several aspects of the plant's architecture (floral structure, pollen cohesiveness, inflorescence structure) are uncompromisingly zoophilous. Estimates of the amount of wind pollination suggest that it is unlikely to be important for the long-distance dispersal of B. napus genes such as those from genetically modified varieties. 5. This study illustrates how CFD may become a powerful tool in future analyses of wind pollination.
Abstract.
Cresswell, J.E. (2004). Carnivorous plants. In Capinera JL (Ed) Encyclopaedia of Entomology, Kluwer Academic Publishers.
Cresswell JE, Osborne JL (2004). The effect of patch size and separation on bumblebee foraging in oilseed rape: implications for gene flow. Journal of Applied Ecology, 41(3), 539-546.
Seymour FA, Cresswell, J.E. Fisher, P.J. Lappin-Scott, H.M. Haag H, Talbot NJ (2004). The influence of genotypic variation on metabolite diversity in populations of two endophytic fungal species. Fungal Genetics and Biology, 41, 721-734.
2003
Cresswell, J.E. (2003). Towards the theory of pollinator-mediated gene flow. Philosophical Transactions of the Royal Society, 358, 1005-1008.
2002
Cresswell JE, Bell SA, Osborne JL (2002). A model of pollinator-mediated gene flow between plant populations with numerical solutions for bumblebees pollinating oilseed rape. Oikos, 98(3), 375-384.
Fenner M, Cresswell, J.E. Hurley, R.A. Baldwin (2002). Relationship between capitulum size and pre-dispersal seed predation by insect larvae in common Asteraceae. Oecologia, 130, 72-77.
2001
Cresswell JE, Hagen C, Woolnough JM (2001). Attributes of individual flowers of Brassica napus L. are affected by defoliation but not by intraspecific competition.
ANNALS OF BOTANY,
88(1), 111-117.
Author URL.
2000
Cresswell JE (2000). A comparison of bumblebees' movements in uniform and aggregated distributions of their forage plant.
Ecological Entomology,
25(1), 19-25.
Abstract:
A comparison of bumblebees' movements in uniform and aggregated distributions of their forage plant
1. Movements by bumblebees Bombus lapidarius were studied in arrays of plants of oil-seed rape Brassica napus cv Westar. In the arrays, plants were arranged into either a uniformly dispersed configuration or a patchily dispersed configuration. 2. Progress across an array was measured as the distance bumblebees had moved away from an original plant location after eight subsequent, successive plant visits. Movements were analysed in units of both metres and inter-plant spaces. In both units, bumblebees progressed more slowly across patchily dispersed arrays. 3. Plant dispersion had a detectable effect on certain components of bees' individual inter-plant moves (e.g. move length in metres) but not on others (e.g. mean turning angle). In some cases, the effects of aggregation on the components of individual moves were probably too small to detect statistically and only emerged in their cumulative effect on bees' progress. 4. Over short sequences of plant visits, bumblebees revisited plants rarely, but the frequency of revisits was almost twice as high in patchy arrays as in uniform arrays, and economic penalties may result from foraging among highly aggregated plants. 5. The effects of plant dispersion on pollinator movements detected in this study are unlikely to have a major impact on pollen transfer in B. napus because differences in pollinator progress only emerged after several successive inter-plant flights away from a potential pollen source, by which time the limited extent of pollen carryover in this species means that fertilisations from the source plant would be very rare.
Abstract.
Cresswell JE, Osborne JL, Goulson D (2000). An economic model of the limits to foraging range in central place foragers with numerical solutions for bumblebees.
Ecological Entomology,
25(3), 249-255.
Abstract:
An economic model of the limits to foraging range in central place foragers with numerical solutions for bumblebees
1. A model is described that evaluates the maximum economic foraging range in central place foragers by using optimality criteria to discriminate between foraging sites at different distances from the forager's central place. 2. The basic model can be varied to suit foragers that optimise either their rate of net energy uptake or their foraging efficiency. 3. The model requires specification of the time and energy budgets of travel and foraging, and of the rewards obtainable at potential foraging sites. 4. The specific case of bumblebees, whose foraging ranges are poorly known, is considered. 5. Numerical solutions of the model for parameter values that represent bumblebees and their forage predict economic foraging ranges exceeding several kilometres. The model demonstrates that economics alone can explain extensive flight ranges in bees.
Abstract.
Cresswell JE (2000). Manipulation of female architecture in flowers reveals a narrow optimum for pollen deposition.
Ecology,
81(11), 3244-3249.
Abstract:
Manipulation of female architecture in flowers reveals a narrow optimum for pollen deposition
The invariability of animal-pollinated flowers relative to vegetative organs, such as leaves, suggests that these flowers may have been finely tuned for an optimum pollination performance. The evolutionary mechanism that could optimize and conserve a species' flower architecture is stabilizing selection, which occurs when intermediate phenotypes attain the highest fitness. Evidence for the operation of such a mechanism is rare in this context, however. Here, I report an experiment that used oil-seed rape (Brassica napus cv. Westar) as the basis of a model system in which the spatial disposition of flowers' sexual organs was manipulated in order to characterize the relationship between form and function. Specifically, individual flowers were manipulated by replacing a section of the style with a length of fine wire in order to produce flowers with pistils of various lengths. The pollination performance of these virgin, model flowers was then assessed by measuring the amount of pollen removed and deposited during a single bumblebee visit. There was no evidence that pollen removal was affected by pistil length. Variation in pistil length, however, was associated with a pronounced optimum in pollen deposition, which was attained by only a narrow range of pistil variants of intermediate length. These results suggest that stabilizing selection may maintain the architectural invariability of animal-pollinated flowers.
Abstract.
Cresswell JE (2000). Resource input and the community structure of larval infaunas of an eastern tropical pitcher plant Nepenthes bicalcarata. Ecological Entomology, 25(3), 362-366.
1999
Cresswell JE (1999). The influence of nectar and pollen availability on pollen transfer by individual flowers of oil-seed rape (Brassica napus) when pollinated by bumblebees (Bombus lapidarius).
Journal of Ecology,
87(4), 670-677.
Abstract:
The influence of nectar and pollen availability on pollen transfer by individual flowers of oil-seed rape (Brassica napus) when pollinated by bumblebees (Bombus lapidarius)
1 Levels of nectar and pollen were manipulated in individual flowers of oil-seed rape, Brassica napus, which were then offered to foraging bumblebees (Bombus lapidarius) for a single visit. 2 the durations of flower visits by bumblebees increased with the amount of nectar, but were unaffected by the level of available pollen. The bees' flower-handling routine may have become behaviourally fixed by the expectation of low pollen rewards, which prevailed in the experimental garden. 3 the effects of nectar provision on both pollen import (deposition on stigma) and export (removal from anthers) were studied. The amount of pollen transferred during a bumblebee's visit was affected only by the amount of pollen that the flower presented. 4 Manipulated flowers that presented a large amount of available pollen received approximately three times more pollen on their stigmas during a bee's visit than flowers with little available pollen, which suggests that autogamous pollen transfer contributes substantially to pollen deposition when pollen availability is high. The gradual dehiscence of the anthers in this species means that available pollen accumulates only if pollinator visits are infrequent, when the increased autogamy may act to ensure adequate pollination. 5 There was no relation between the quantity of nectar residue that a bee left after visiting a manipulated flower and the mean duration of its visits to unmanipulated flowers. Therefore, variation among individuals in the duration of visits to unmanipulated flowers apparently resulted from differences in foraging speed rather than from variation in the thoroughness of nectar removal.
Abstract.
1998
Cresswell JE (1998). Morphological correlates of necromass accumulation in the traps of an Eastern tropical pitcher plant, Nepenthes ampullaria Jack, and observations on the pitcher infauna and its reconstitution following experimental removal.
Oecologia,
113(3), 383-390.
Abstract:
Morphological correlates of necromass accumulation in the traps of an Eastern tropical pitcher plant, Nepenthes ampullaria Jack, and observations on the pitcher infauna and its reconstitution following experimental removal
I studied the trap morphology, necromass accumulation rates and pitcher infauna of an eastern tropical pitcher plant, Nepenthes ampullaria, that grew in 'kerangas' heath forest in the Sungei Ingei Conservation Area, Brunei. I surveyed 164 pitchers distributed among 35 plants and extracted the necromass and larval infauna from the pitchers and then resampled the pitcher contents after 14 days. Plants varied significantly in the morphology of their pitchers, in their rate of necromass accumulation per pitcher and in the abundance and composition of the pitcher infaunas. On average, pitchers accumulated 11.5 mg dry weight over 14 days, but larger pitchers accumulated more necromass than smaller ones. Pitcher morphology explained 45% of the variation in necromass accumulation among plants. On average, pitchers initially contained 26.3 individual larval inquilines. Collectively, the larval infauna was composed of nine taxa of dipteran larvae and infrequent anuran tadpoles. These ten taxa were never found together in a single pitcher and the mean species richness per pitcher was 4.0. of the six taxa that could be assessed, all except Toxorhynchites spp. had a contagious distribution among the pitchers. Pitcher morphology and necromass accumulation explained only 15% of the variation in inquiline abundance among plants. I found little evidence for the existence of density-dependent interactions between inquiline species: a partial correlation analysis detected only one statistically significant pairwise relationship between the abundances of inquiline taxa, which was a positive association. Fourteen days after being emptied, pitchers contained an average of 9.6 inquilines. There was no evidence that the species composition of the infauna recolonizing each pitcher was related to that of its pre-removal infauna.
Abstract.
Cresswell JE (1998). Stabilizing selection and the structural variability of flowers within species.
Annals of Botany,
81(4), 463-473.
Abstract:
Stabilizing selection and the structural variability of flowers within species
Zoophilous flowers often appear to be precisely formed for pollen transfer and exhibit relatively little variability in structure within species. Functional optimization by the seemingly exacting requirements of pollen transfer may account for these observations. I used the results of a literature survey to examine the levels of intraspecific variation in flowers across a wide range of taxa. The least variable attributes were those potentially affecting the mechanical fit between flower and pollinator, which are potentially constrained by selection for pollination performance. I discuss six mechanisms by which plant-pollinator interactions could generate stabilizing selection on flowers. In addition, I consider the stabilizing roles of limiting resources and also two functionally-neutral mechanisms. Further work is required to identify the actual mechanisms by which selection stabilizes the evolution of flowers.
Abstract.
Bell SA, Cresswell JE (1998). The phenology of gender in homogamous flowers: Temporal change in the residual sex function of flowers of Oil-seed rape (Brassica napus).
Functional Ecology,
12(2), 298-306.
Abstract:
The phenology of gender in homogamous flowers: Temporal change in the residual sex function of flowers of Oil-seed rape (Brassica napus)
1. We investigated the phenology of the male and female sexual functions in flowers of Oil-seed Rape (Brassica napus) that were exposed to pollinators in an experimental garden. The female residual sex function' (RSF) of flowers was measured by hand- pollinating with genetically marked pollen in order to determine the proportion of ovules that remained available for fertilization by incoming pollen. Male RSF was measured by estimating the proportion of pollen grains that remained in dehiscing anthers. 2. Following flower opening, an average flower's male and female sexual functions each required for completion c. 13 h of exposure to pollinators. One hour after opening, c. 50% of a flower's ovules were unavailable to incoming pollen whereas on y c. 10% of pollen was removed. Therefore, a flower's sexual function was predominantly female for the first hour and predominantly male thereafter. 3. We found a fairly close correspondence between the proportion of the stigma covered with pollen and the depletion of female RSE on average, floral senescence occurred after c. 14.5 h of exposure to pollinators. Our observations are fairly consistent with a simple, economic model of optimal senescence time because the flowers remained open for approximately the same length of time as was necessary for the completion of their sexual functions. 5. A flower's senescence was hastened when pollen was removed from the anthers, but not when pollen was deposited on the stigma. 6. When flowers were either left undisturbed or hand-pollinated, senescence occurred after c. 24 h. Pollen removal caused senescence after c. 13 h, which also approximated the longevity of flowers in the experimental garden. Apparently, pollen removal governed floral longevity under field conditions.
Abstract.
1997
Cresswell JE (1997). Spatial heterogeneity, pollinator behaviour and pollinator-mediated gene flow: Bumblebee movements in variously aggregated rows of oil-seed rape.
Oikos,
78(3), 546-556.
Abstract:
Spatial heterogeneity, pollinator behaviour and pollinator-mediated gene flow: Bumblebee movements in variously aggregated rows of oil-seed rape
The foraging movements of bees are said to be influenced by the spatial distribution of the plants whose flowers they visit. However, Manasse found that bee-mediated gene flow was unrelated to the degree of aggregation among the plants in the linear arrays that be studied. To investigate this apparent contradiction further, I manipulated the levels of aggregation in linear plant arrays and examined both the effect of the movements of the bumblebee pollinators and the likely consequences for pollen dispersal and gene flow. I studied pollinator movements among plants of oil-seed rape (Brassica napus ev. Westar) that were arranged in rows that each contained 50 plants. In each experiment one row of plants was spaced at uniform intervals and the remaining rows contained aggregated plant distributions. Experiments were conducted at two scales, short rows (10 ml) and long rows (20 m). The plants were visited almost exclusively by worker caste individuals of Bombus lapidarius. Bumblebees were followed over successive visits within a row and location of each visited plant and the number of flowers probed there was recorded. Within each row, I examined the following components of bumblebee behaviour; the mean number of flowers probed per plant visit; the meant interplant flight distance; and the mean directionality (proportion of moves in an individual's favoured direction). The collective movements of bumblebees within each row were characterised by the rate of change of the bees mean squared distance from an original location. The spatial dispersion of pollen from a paternal plant was estimated in each row by combining a quantitative description of bumblebee movements in terms of displacement from a paternal plant with a model of pollen deposition. Bumblebees were observed to visit many plants successively within a row and movements between rows were infrequent. In both long and short rows, three components of bumblebee movement behaviour were significantly modified by the level of plant aggregation. With increasing plant aggregation, bumblebees exhibited a decrease in directionality and in the number of flowers probed per plant visit and they exhibited an increase in the number of plants by-passed during interplant flights. Despite the effect of plant aggregation on the components of bumblebee behaviour, the bumblebees collective rate of movement away from an origin within a row was unrelated to the level of plant aggregation. This was consistent with the finding that plant aggregation did not significantly affect either the estimates of mean pollen dispersal distances measured in metres or a plant's expected number of female mates. The modifications to bumblebee behaviour that were caused by differential aggregation among rows apparently combined, fortuitously, to buffer the spatial extent of pollen dispersal. Consequently, my results are consistent with heterogeneity at these scales. However, I also conclude that the effects of plant aggregation on gene flow will depend on the spatial scale of the inter-patch distances.
Abstract.
Belisle C, Cresswell J (1997). The effects of a limited memory capacity on foraging behavior.
THEORETICAL POPULATION BIOLOGY,
52(1), 78-90.
Author URL.
1996
Cresswell JE, Bassom AP, Bell SA, Collins SJ, Kelly TB (1996). Predicted pollen dispersal by honey-bees and three species of bumble-bees foraging on oil-seed rape: a comparison of three models. Functional Ecology, 9(6), 829-841.
1995
Cresswell JE, Vidal-Martinez VM, Crichton NJ (1995). The investigation of saturation in the species richness of communities: Some comments on methodology. Oikos, 72(2), 301-304.
1994
Cresswell JE (1994). A method for quantifying the gene flow that results from a single bumblebee visit using transgenic oilseed rape, Brassica napus L. cv. Westar.
Transgenic Research,
3(2), 134-137.
Abstract:
A method for quantifying the gene flow that results from a single bumblebee visit using transgenic oilseed rape, Brassica napus L. cv. Westar
Genetically modified plants containing selectable markers offer a unique opportunity for pollination biologists to investigate some of the major, but intractable questions about paternity distributions and their causes. Here, a method is reported that uses transgenic plants to enable the quantification of the outcrossed fertilizations that result from a single pollinator visit. Gene flow mediated by worker bumblebees (Bombus terrestris) was studied among plants of oilseed rape (Brassica napus L. cv. Westar) where transgenic paternity in seeds of a non-transgenic plant was manifested as herbicide resistance. Overall, 91% of the resistant seeds resulted from the first four flowers that were visited after the bumblebee left the transgenic plant, and none was found beyond the 14th successively visited flower. The possibilities for developing the method to address various questions in pollination biology are discussed. © 1994 Chapman & Hall.
Abstract.
Cresswell JE, Robertson AW (1994). Discrimination by pollen-collecting bumblebees among differentially rewarding flowers of an alpine wildflower, Campanula rotundifolia (Campanulaceae). Oikos, 69(2), 304-308.
1993
CRESSWELL JE (1993). THE MORPHOLOGICAL CORRELATES OF PREY CAPTURE AND RESOURCE PARASITISM IN PITCHERS OF THE CARNIVOROUS PLANT SARRACENIA-PURPUREA.
AMERICAN MIDLAND NATURALIST,
129(1), 35-41.
Author URL.
1992
CRESSWELL JE, MERRITT SZ, MARTIN MM (1992). THE EFFECT OF DIETARY NICOTINE ON THE ALLOCATION OF ASSIMILATED FOOD TO ENERGY-METABOLISM AND GROWTH IN 4TH-INSTAR LARVAE OF THE SOUTHERN ARMYWORM, SPODOPTERA-ERIDANIA (LEPIDOPTERA, NOCTUIDAE).
OECOLOGIA,
89(3), 449-453.
Author URL.
1991
CRESSWELL JE, SAYRE CF (1991). CAN EVOLUTIONARILY STABLE STRATEGIES EXIST.
OIKOS,
60(3), 382-385.
Author URL.
CRESSWELL JE (1991). CAPTURE RATES AND COMPOSITION OF INSECT PREY OF THE PITCHER PLANT SARRACENIA-PURPUREA.
AMERICAN MIDLAND NATURALIST,
125(1), 1-9.
Author URL.
Cresswell JE, Galen C (1991). Frequency-dependent selection and adaptive surfaces for floral character combinations: the pollination of Polemonium viscosum.
American Naturalist,
138(6), 1342-1353.
Abstract:
Frequency-dependent selection and adaptive surfaces for floral character combinations: the pollination of Polemonium viscosum
The pollination success obtained from a bumblebee visit by an individual of Polemonium viscosum depends on the size of nectar rewards offered and weakly on flower size but, probably because the size of nectar rewards correlates with flower size, bumblebees discriminate among individual plants on the basis of flower size. If preferences are learned, then it is likely that the nature of the preferences will depend on the bees' experience with reward/advertisement combinations and that this will be affected by the frequenciies of the combinations in the population. In general, when the pollination performance of plants is determined in part by pollinator visitation rate, then the adaptive surfaces that Armbruster proposed for the study of relationships beteen form and function in flowers may alter under frequency-dependent selection. The shape of the adaptive surface may depend on population composition under the following conditions: intraspecific competition for pollinators, a correlation between nectar production rate and standing crop of nectar, and a correlation of standing crop of nectar with a component of a floral advertisement that can be learned by the pollinator. -from Authors
Abstract.
1990
CRESSWELL JE (1990). HOW AND WHY DO NECTAR-FORAGING BUMBLEBEES INITIATE MOVEMENTS BETWEEN INFLORESCENCES OF WILD BERGAMOT MONARDA-FISTULOSA (LAMIACEAE).
OECOLOGIA,
82(4), 450-460.
Author URL.
