Behavioural and molecular responses to pesticide exposure in bumblebees

Lead Research Organisation: Imperial College London
Department Name: Life Sciences

Abstract

With globally growing human populations there is ever increasing demand for higher agricultural yields. Pesticides are applied to maintain high crop yields, but we know little about the effects that current pesticide use has on non-target organisms including the beneficial pollinators that visit these crops. The most important of such pollinators are the social bees (e.g. honey bees and bumble bees) - but their populations have recently been declining, posing important risks for food security and the global economy. Pesticides have been implicated in these declines, yet to date there is a great paucity of data to show whether pesticide exposure at field levels is actually having an effect on bees.

Field level pesticide exposure is typically non-lethal to bees; so why should we be concerned? Recent studies have highlighted that pesticides approximating field levels may induce sublethal effects on individual bee behaviour. The concern is therefore that such effects at the individual level may have knock on effects to colony reproduction and survival, and this would explain observed bee declines. However, there are almost no studies that have set out to show whether this is indeed the case. Furthermore, we still lack an understanding about the manner in which foraging bees are affected at both the behavioural and molecular (genetic) level. The importance of understanding the subtle or large effects of pesticide exposure on foraging performance should not be underestimated: i) colony growth relies directly on efficient foraging and ii) any impairment to foraging performance has direct consequences on the successful pollination of crops and wild flowers. It is thus a research priority to know how a pesticide exposure landscape affects bee foraging behaviour, how this affects colony success, and ultimately how this shapes bee populations.

We propose to carry out five axes of research that will address these gaps in our knowledge. Our study system will be bumblebees (Bombus spp), as bumblebees are one of the most substantial wild insect pollinators in the landscape, as well as being used for greenhouse pollination. First we will determine whether pesticides reduce the abilities of bumblebees to carry out complex pollination tasks. Second, we will determine whether this in turn affects colony growth and reproductive success. Third, we will determine whether exposure to pesticides affects the yield of the crops bumblebees are pollinating. Fourth, using tools previously only available to cancer researchers, we will identify the molecular changes that occur in bees when they are exposed to pesticides. Finally, by performing genetic screening on five species of wild bumblebees sampled from across the UK we will determine the extent to which pesticides affect wild bumblebee populations. If impairment to foraging behaviour induced by pesticide exposure has an effect on colony fitness then we expect there to be a strong selective pressure shaping bee populations.

Planned Impact

The pollination service that bee pollination provides has an economic value of >£300 million in the UK alone (>$150bn p.a. globally) Therefore, any study that can identify the factors causing bee declines and help mitigate it is fundamentally important for food security, our economy and the environment. There are thus numerous interested parties that would be interested:

1) It will provide important data to inform pesticide regulatory authorities on the ecotoxicological testing guidelines for application of specific pesticides in order to reduce the risk posed to beneficial pollinators. It will also provide data to better inform regulators about the appropriate duration that toxicity testing should be carried out for to detect chronic effects (if any). Currently, the guidelines for ecotoxicological testing of pesticides does not consider methods which would detect sublethal effects, and nor does it ask for testing to be longer than 96 hours.

2) The data will inform the EU about whether the current restriction of three of the seven neonicotinoids should lead to: i) a permanent ban; ii) a prolonged suspension; iii) a lifted suspension and return to previous application procedures; or iv) a lifted suspension but with modified application guidelines. Moreover, our tests will look at the other four un-restricted neonicotinoids which will tell us whether they appear to be better alternatives or pose a greater threat than those that are currently restricted.

3) We expect that work such as this has the potential to change policy, especially if we consider that our previous work (Gill et al. 2012, Nature) was used to debate and influence the EU moratorium.

4) As has been evident over the past year, there is large appeal of bees to the general public. For instance the press interest surrounding the decline of bees and its impact on food security, and the protest outside parliament in April 2013 about bees and the effects of neonicotinoids, undeniably supports this.

5) We will actively seek to communicate and build knowledge exchange relationships with pesticide regulatory directorates (to inform policy & application guidelines), environmental agencies and conservation trusts (to inform about the risks posed to beneficial pollinators), farming unions (to make aware which practices pose a threat to the pollination service their crops rely on), stakeholders and beekeepers (to help protect bees), and the general public (public awareness) to disseminate the results of our research in the most effective way.

6) The outreach offices (Imperial & QMUL) have also expressed interest in creating pamphlets to summarise our research to an audience which would comprise primarily of farmers and the general public.

Publications

10 25 50

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Colgan TJ (2022) Genomic Signatures of Recent Adaptation in a Wild Bumblebee. in Molecular biology and evolution

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Rother L (2021) A micro-CT-based standard brain atlas of the bumblebee. in Cell and tissue research

 
Description Whilst the award period has finished, there are still a number of analyses being undertaken with key findings still to come (particularly on the molecular aspect of the project).
Achieved so far:
1. Publication in J. Applied Ecology showing the effect that neonic pesticide exposure can have on bee colony reproduction, which was shown using a novel method of semi-field setup.
2. Publication in Proc. Roy. Soc. B showing that the risk of neonic exposure to bees is higher than previously thought, as foraging experiments showed bees exhibiting signs of addiction with chronic exposure.
3. Publication in Proc. Roy. Soc. B showing that pesticide exposure during larval development affects brain growth and predisposes adult workers to be poor learners
4. Publication in Molecular Ecology showing changes in gene expression when exposed to two specific neonic pesticides and that responses are different between castes.

Ongoing (manuscripts in preparation)
1. Gut microbiome of multiple bee species across UK
2. Gut microbiome responses to pesticide exposure
3. Population genomics of a common bumblebee reveals signatures of selection from agricultural land-use change (under review)

The genomic data and analytical pipelines are currently also informing another NERC funded project.
Exploitation Route Our findings are very important for risk assesment of pesticide use, and our work helped to inform the EFSA to implement the recent EU ban on three neonics .
Management of honeybee hives, bumblebee colonies and conservation of wild bees can act on our findings
Our methods can also be adopted by pesticide regulatory testing procedures, and it is of use for farmers, conservationists, apidologists (bee keepers) and land managers.

The work still in preparation will provide us with an understanding of how agricultutral practices have shaped our bee population over the past century.
Sectors Agriculture

Food and Drink

Chemicals

Education

Environment

Manufacturing

including Industrial Biotechology

Other

 
Description Publication in Journal of Applied Ecology was considered in the EFSA review of the risk of neonicotinoids to bees leading to a EU moratorium. Andres Arce who was postdoc on this grant is currently a member of the academic panel advising on the new risk assessment guidance for the risk to insect pollinators posed by pesticide use. The current publications from this grant are being used to inform this process. Findings in the publication in Proc Roy Soc B show that neonicotinoid treated field may actually be attractive to bees, and is being considered by environmental policy when determine re-assessment of risk to bees, particularly post-Brexit. Publication in Mol Biol & Evol provides whole genome sequencing of wild bumblebees and revealed areas of the genome under selection. This provides a new molecular resource that is useful for other academics and genome biologists.
First Year Of Impact 2016
Sector Agriculture, Food and Drink,Chemicals,Environment,Government, Democracy and Justice,Other
Impact Types Policy & public services

 
Description Helped inform the European Commission SEP 2020 future brief on the importance of pollinators for human wellbeing
Geographic Reach Europe 
Policy Influence Type Citation in other policy documents
Impact My work helped inform policy on where focus shod be placed to support pollinator populations to support human wellbeing. Importance for nature and human well-being, drivers of decline, and the need for monitoring
URL https://op.europa.eu/en/publication-detail/-/publication/ddcb6a5e-ca33-11ea-adf7-01aa75ed71a1
 
Description BES Large Research Grant
Amount £17,000 (GBP)
Organisation British Ecological Society 
Sector Charity/Non Profit
Country United Kingdom
Start 03/2017 
End 09/2017
 
Title Data from: Foraging bumblebees acquire a preference for neonicotinoid-treated food with prolonged exposure 
Description Social bees represent an important group of pollinating insects but can be exposed to potentially harmful pesticides when foraging on treated or contaminated flowering plants. To investigate if such exposure is detrimental to bees, many studies have exclusively fed individuals with pesticide spiked food, informing us about the hazard but not necessarily the risk of exposure. Whilst such studies are important to establish the physiological and behavioural effects on individuals they do not consider the possibility that exposure may change over time. For example, many pesticide assays exclude potential behavioural adaptations, such as a rejection of harmful compounds by choosing to feed on an uncontaminated food source, which would behaviourally lower the risk of exposure. Here we conducted an experiment over 10 days in which bumblebees forage on an array of sucrose feeders containing a range of concentrations (0, 2 & 11 parts per billion) of the neonicotinoid pesticide thiamethoxam. We more closely mimic pesticide exposure in the wild by allowing foraging bees to experience i) a range of pesticide concentrations across a chronic exposure period, ii) repeated interactions with the pesticide, and iii) allowing foraging bees to retain the social cues associated with foraging by using whole colonies. We found that the proportion of visits to pesticide-laced feeders increased over time, resulting in the consumption of more pesticide-laced sucrose. After changing the spatial position of each feeder, foragers continued to preferentially visit the pesticide-laced food, indicating that workers can detect thiamethoxam and alter their behaviour to continue feeding from it. The increasing preference for consuming the neonicotinoid treated food, therefore increases the risk of exposure for the colony during prolonged pesticide exposure. Our results highlight the need to incorporate attractiveness of field relevant concentrations of pesticides to foraging bees (and other insect p 
Type Of Material Database/Collection of data 
Year Produced 2018 
Provided To Others? Yes  
URL https://datadryad.org/stash/dataset/doi:10.5061/dryad.4f6t3b5
 
Title Data from: Impact of controlled neonicotinoid exposure on bumblebees in a realistic field setting 
Description Pesticide exposure has been implicated as a contributor to insect pollinator declines. In social bees, which are crucial pollination service providers, the effect of low-level chronic exposure is typically non-lethal leading researchers to consider whether exposure induces sublethal effects on behaviour and whether such impairment can affect colony development. Studies under laboratory conditions can control levels of pesticide exposure and elucidate causative effects, but are often criticized for being unrealistic. In contrast, field studies can monitor bee responses under a more realistic pesticide exposure landscape; yet typically such findings are limited to correlative results and can lack true controls or sufficient replication. We attempt to bridge this gap by exposing bumblebees to known amounts of pesticides when colonies are placed in the field. Using 20 bumblebee colonies, we assess the consequences of exposure to the neonicotinoid clothianidin, provided in sucrose at a concentration of five parts per billion, over 5 weeks. We monitored foraging patterns and pollen collecting performance from 3282 bouts using either a non-invasive photographic assessment, or by extracting the pollen from returning foragers. We also conducted a full colony census at the beginning and end of the experiment. In contrast to studies on other neonicotinoids, showing clear impairment to foraging behaviours, we detected only subtle changes to patterns of foraging activity and pollen foraging during the course of the experiment. However, our colony census measures showed a more pronounced effect of exposure, with fewer adult workers and sexuals in treated colonies after 5 weeks. Synthesis and applications. Pesticide-induced impairments on colony development and foraging could impact on the pollination service that bees provide. Therefore, our findings, that bees show subtle changes in foraging behaviour and reductions in colony size after exposure to a common pesticide, have important implications and help to inform the debate over whether the benefits of systemic pesticide application to flowering crops outweigh the costs. We propose that our methodology is an important advance to previous semi-field methods and should be considered when considering improvements to current ecotoxicological guidelines for pesticide risk assessment. 
Type Of Material Database/Collection of data 
Year Produced 2017 
Provided To Others? Yes  
URL https://datadryad.org/stash/dataset/doi:10.5061/dryad.245kq
 
Title Data from: Lower bumblebee colony reproductive success in agricultural compared to urban environments 
Description Urbanisation represents a rapidly growing driver of land-use change. While it is clear that urbanisation impacts species abundance and diversity, direct effects of urban land-use on animal reproductive success are rarely documented. Here we show that urban land-use is linked to long-term colony reproductive output in a key pollinator. We reared colonies from wild-caught bumblebee (Bombus terrestris) queens, placed them at sites characterised by varying degrees of urbanisation from inner city to rural farmland, and monitored the production of sexual offspring across the entire colony cycle. Our land-use cluster analysis identified three site categories, and this categorization was a strong predictor of colony performance. Crucially, colonies in the two clusters characterized by urban development produced more sexual offspring than those in the cluster dominated by agricultural land. These colonies also reached higher peak size, had more food stores, encountered fewer parasite invasions and survived for longer. Our results show a link between urbanisation and bumblebee colony reproductive success, supporting the theory that urban areas provide a refuge for pollinator populations in an otherwise barren agricultural landscape. 
Type Of Material Database/Collection of data 
Year Produced 2018 
Provided To Others? Yes  
URL https://datadryad.org/stash/dataset/doi:10.5061/dryad.c68cj62
 
Title Data from: Pesticide exposure affects flight dynamics and reduces flight endurance in bumblebees 
Description The emergence of agricultural land use change creates a number of challenges that insect pollinators, such as eusocial bees, must overcome. Resultant fragmentation and loss of suitable foraging habitats, combined with pesticide exposure, may increase demands on foraging, specifically the ability to collect or reach sufficient resources under such stress. Understanding effects that pesticides have on flight performance is therefore vital if we are to assess colony success in these changing landscapes. Neonicotinoids are one of the most widely used classes of pesticide across the globe, and exposure to bees has been associated with reduced foraging efficiency and homing ability. One explanation for these effects could be that elements of flight are being affected, but apart from a couple of studies on the honeybee (Apis mellifera), this has scarcely been tested. Here, we used flight mills to investigate how exposure to a field realistic (10 ppb) acute dose of imidacloprid affected flight performance of a wild insect pollinator-the bumblebee, Bombus terrestris audax. Intriguingly, observations showed exposed workers flew at a significantly higher velocity over the first ¾ km of flight. This apparent hyperactivity, however, may have a cost because exposed workers showed reduced flight distance and duration to around a third of what control workers were capable of achieving. Given that bumblebees are central place foragers, impairment to flight endurance could translate to a decline in potential forage area, decreasing the abundance, diversity, and nutritional quality of available food, while potentially diminishing pollination service capabilities. 
Type Of Material Database/Collection of data 
Year Produced 2019 
Provided To Others? Yes  
URL https://datadryad.org/stash/dataset/doi:10.5061/dryad.gd702q0
 
Title Supplementary Tables from Lower bumblebee colony reproductive success in agricultural compared to urban environments 
Description Supplementary tables including model selection tables and estimates and confidence intervals for statistical analyses presented and details of Principle Components Analysis for land classification 
Type Of Material Database/Collection of data 
Year Produced 2018 
Provided To Others? Yes  
URL https://rs.figshare.com/articles/dataset/Supplementary_Tables_from_Lower_bumblebee_colony_reproducti...
 
Title Supplementary Tables from Lower bumblebee colony reproductive success in agricultural compared with urban environments. 
Description Supplementary tables including model selection tables and estimates and confidence intervals for statistical analyses presented and details of Principle Components Analysis for land classification 
Type Of Material Database/Collection of data 
Year Produced 2018 
Provided To Others? Yes  
URL https://rs.figshare.com/articles/dataset/Supplementary_Tables_from_Lower_bumblebee_colony_reproducti...
 
Title Supplementary Tables from Lower bumblebee colony reproductive success in agricultural compared with urban environments. 
Description Supplementary tables including model selection tables and estimates and confidence intervals for statistical analyses presented and details of Principle Components Analysis for land classification 
Type Of Material Database/Collection of data 
Year Produced 2018 
Provided To Others? Yes  
URL https://rs.figshare.com/articles/dataset/Supplementary_Tables_from_Lower_bumblebee_colony_reproducti...
 
Description Effects of urbanisation on bees 
Organisation Royal Holloway, University of London
Country United Kingdom 
Sector Academic/University 
PI Contribution Co-supervised two BBSRC funded PhD students, and providing help through an advisory capacity
Collaborator Contribution Undertook empirical experiments looking at bee responses to land use and pesticide exposure, and modeling of foraging movements in bees.
Impact 1. Palmer et al. in prep. 2. DOI: 10.1007/s13592-020-00758-1 3. DOI: 10.1098/rspb.2018.0807 4. DOI: 10.1038/srep38957
Start Year 2016
 
Description Molecular responses to pesticide exposure in bees 
Organisation Queen Mary University of London
Department School of Biological and Chemical Science QMUL
Country United Kingdom 
Sector Academic/University 
PI Contribution We are looking at population genomics and gene expression studies for multiple native bumblebee populations across the UK. My group carried out the field sampling, identifications, prepration, DNA extractions, and help with library preps for the molecular work to be undertaken, as well as controlled exposure assays. This has then fed into the work carried out by the collaborators.
Collaborator Contribution Managed the DNA and RNA sequencing and undertaken the bioinformatics required to address the questions posed.
Impact 1. Colgan et al. under review Genome Biology 2. DOI: 10.1111/mec.15047 3. DOI: 10.1098/rspb.2018.0655 4. DOI: 10.1111/1365-2664.12792 The collaboration is multi-disciplinary.
Start Year 2014
 
Description Beekeepers Association meeting 2021 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact Presented research on the risk of pesticide to bees
Year(s) Of Engagement Activity 2021
 
Description Central Bekeepers association 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact Central Beekeepers association invited me as speaker to discuss the threats facing bees
Year(s) Of Engagement Activity 2016
 
Description Imperial Science Breaks 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact Imperial Science Breaks to showcase our work studying the unsung heroes of agriculture.
https://www.youtube.com/watch?v=MOrK0u_jIPA
Year(s) Of Engagement Activity 2020
URL https://www.imperial.ac.uk/events/125601/science-breaks-unseen-organisms-and-unsung-heroes/
 
Description Invited talk on bee research - CNRS 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Other audiences
Results and Impact Presented work to researchers at the CNRS in Toulouse, France
Year(s) Of Engagement Activity 2020
 
Description Milan Expo 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Milan Expo - Invited to the UK exposition (the Hive) and presented and discussed threats to insect pollinators
Year(s) Of Engagement Activity 2015
 
Description POST meeting on understanding insect declines 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Policymakers/politicians
Results and Impact Parliamentary Office for Science & Technology. I contributed to a POST note and report on understanding insect declines, and then attended parliament to provide an expert opinion in using next-generation molecular techniques to study and monitor insects.
Year(s) Of Engagement Activity 2020
URL https://post.parliament.uk/research-briefings/post-pb-0036/
 
Description Royal Entomological Society Invited Speaker on Insect Declines 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Other audiences
Results and Impact nvited Speaker on Insect Declines - talked about my current work adressing this issue
Year(s) Of Engagement Activity 2019
 
Description Royal Entomological Society special interest group 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Other audiences
Results and Impact Using new technologies to study insects
Year(s) Of Engagement Activity 2015