Search

Wildflower plantings are a key tool for wild bee conservation, and plant–bee interaction data are frequently used in seed mix design to ensure that plantings provide sufficient resources for a diversity of bees. Plant–bee interaction data are also used in monitoring programmes to measure the success of bee‐supporting habitat. However, collecting plant–bee interaction data can be expensive and these data are not used by many seed mix design practitioners and monitoring programmes. Therefore, a crucial question is how does the conservation value of seed mixes vary as a function of the intensity of the data collection effort underpinning their design?We leverage a plant–bee interaction data set to ask how bee richness is expected to change when informed by different scenarios of reduced data collection effort and cost. From the original, large data set, we created subsets of data by randomly reducing (1) the number of specimens sampled, (2) the number of sites sampled, (3) the number of sampling days per site and (4) using data from a single, representative taxon (bumble bees). We ask whether seed mixes designed from these reduced data sets support comparable bee richness to the full data set, and for any reduction in cost.Reductions in the number of specimens sampled and the number of sampling days per site yield seed mixes that support comparable bee richness to the full data set. Reductions in the number of sites yielded seed mixes that support lower bee richness than the full data set. Using bumble bee interaction data only yields seed mixes that support lower bee richness than the full data set, especially when few plants are included in the mixes.Synthesis and applications. We recommend prioritizing broad spatial, temporal and taxonomic coverage of plant–bee interaction data to guide cost‐effective seed mix design. Our results also provide guidance for practitioners designing programmes to monitor bee richness in restored habitat because plant–bee interaction data may be made cheaper by collecting fewer specimens per sampling event or collecting on fewer dates per site (as long as coverage of the full bee flight season is maintained). [ABSTRACT FROM AUTHOR]

Bees are essential pollinators of crops and wild plants and their ability to forage and pollinate are key aspects of their behaviour. Bee populations are under threat, with the use of insecticides a contributing factor. Most research has focused on neonicotinoid insecticides and bee mortality, and little is known about impacts on bee foraging and delivery of pollination services. However, other insecticide classes, such as organophosphates and pyrethroids, are increasingly used globally, but little is known about how these widely used substances may impact bees, particularly non‐honeybees.We exposed bumblebee Bombus terrestris colonies to field‐relevant doses of a pyrethroid (lambda‐cyhalothrin) and an organophosphate (dimethoate) and investigated sublethal effects on behaviour at the individual and colony level, in addition to pollination service delivery under semi‐field conditions.We show, for the first time, that exposure to these chemicals impacts the activity and pollen provisioning of bumblebee Bombus terrestris audax colonies, while no short‐term effects on flower handling behaviour or pollination service delivery were detected.We found that colonies exposed to dimethoate were less active, with 67% fewer bees leaving the colony to forage than control colonies, and of those that returned, 92% fewer returned pollen provisions to the nest. Colonies exposed to lambda‐cyhalothrin did not differ in activity; however, 62% fewer of these bees returned with pollen provisions.Policy implications. These findings give important insights into how exposure to different classes of insecticides could impact bumblebee activity and their provision of pollen required for colony development. With a focus on neonicotinoids in terms of policy changes regarding insecticides and bees, we show that other insecticide classes should also be re‐examined in relation to their potential risks for pollinators. We confirm the need to improve risk assessment of insecticides to assess sublethal effects, include non‐honeybee species in risk assessment processes and also consider key behaviours such as foraging and interactions with plants. [ABSTRACT FROM AUTHOR]

Anthropogenic pressures on native ecosystems have resulted in numerous functional and compositional changes, creating novel ecosystems with new interactions between native and exotic species. How native species utilize these resources is crucial for their management in altered landscapes and the promotion of their essential ecosystem services.We compared seasonal floral selection between European honey bees and their most phylogenetically similar native component in our study region, bumble bees, in North American grasslands with high densities of exotic plant species. Additionally, we determined whether floral species richness, total flowering density, native floral density or exotic floral density best explained the abundance of both groups.Selection analyses revealed that honey bees and native bumble bees differed in selection between native and non‐native floral resource availability, with any significant selection of honey bees being for exotic plants while native bumble bees selected for native plants.Native forb presence and floral richness best explained the variation in bumble bee abundance, while honey bee abundance was associated with flowering densities in the early and mid‐seasons and floral richness in both the early and late seasons.Despite their generalist diets, we emphasize the importance of native floral availability for bumble bee foraging in novel grassland landscapes and the importance of exotic plants to support honey bee production.Synthesis and applications. Our results indicate that pollinator forage management should differ for non‐native and native species, despite morphological and life‐history similarities. However, greater floral diversity provides a common management focus that can benefit honey bees and bumble bees in particular seasonal periods. Our results suggest that management actions promoting resource diversity can benefit functionally different species. In grasslands, implementing disturbance processes that can favour floral expression (e.g. fire; grazing) can support bumble bees of conservation concern and agriculturally important bees simultaneously. [ABSTRACT FROM AUTHOR]

Biodiversity linked to traditionally managed semi‐natural grasslands is declining, despite conservation efforts. At the same time, the area of novel grassland habitats along linear infrastructure, such as road verges and power line corridors, is increasing and in some regions surpass the area of semi‐natural grasslands. An open question is to what extent these novel grasslands can complement or even replace traditionally managed grasslands as habitat for grassland species.We compared the alpha (species richness) and beta (abundance‐based dissimilarities) diversity of plants, bumblebees and butterflies among semi‐natural pastures, verges of small and big roads, power line corridors and uncultivated field borders nested within 32 landscapes (2 × 2 km squares). Landscapes had either high or low road density and were with or without power line corridors. Across landscapes there was also a gradient in the area of semi‐natural pastures.Alpha diversity of all three species groups was as high in power line corridors and verges of small roads as in semi‐natural pastures, regardless of landscape composition. Although all habitat types shared a large proportion of species, community composition differed among habitats for all three species groups. The beta diversity of plants and butterflies was driven primarily by the replacement of species (turnover), while the beta diversity of bumblebees was driven by a rarer occurrence of certain species in road verges (nestedness). This means that linear infrastructure habitats cannot fully replace the role of semi‐natural grasslands for plant and pollinator diversity.The area of road verges, power line corridors and semi‐natural pastures in the landscape influenced community composition of plants and butterflies, but not the similarity in community composition among habitats within landscapes.Policy implications. Although novel grasslands along linear infrastructures have high numbers of grassland species, they only support a part of the biodiversity found in traditionally managed semi‐natural grasslands. Therefore, protecting and restoring semi‐natural grasslands should continue to be a priority for the conservation of grassland biodiversity. However, especially in landscapes where the area of semi‐natural grasslands is low, road verges and power line corridors can be important habitats for a number of grassland plants and insects and should be managed to promote biodiversity. [ABSTRACT FROM AUTHOR]

Sustainable food production requires agriculture to conserve biodiversity and facilitate ecosystem services to maintain productivity levels while reducing inputs detrimental to ecosystem functioning. Increasing within‐field vegetation diversity by legume intercropping seems promising to facilitate cropping system multi‐functionality. Effects of intercropping with legumes on biodiversity‐mediated ecosystem services such as pollination or natural pest control are, however, not sufficiently understood.Using 26 observation plots in a paired field design, we studied the effects of undersowing oats with a mixture of three annual clovers across different aspects of cropping system multi‐functionality. We investigated 16 below‐ and above‐ground ecosystem service indicators related to soil mineral nitrogen, arable weed control, pollination, disease and pest pressures, natural pest control and crop yield.We found lower arable weed cover, higher flower cover and pollinator densities as well as decreased root‐feeding nematode densities in intercropped observation plots compared with the non‐intercropped controls. However, intercropping decreased spider activity densities and oat yield nitrogen content. Root diseases, pest damages, natural pest control and crop yield were not affected by intercropping.The biomass of undersown clovers was positively related with the differences in flower cover and pollinator densities, and negatively related with the differences in arable weed cover between the intercropped and the control treatment.Synthesis and applications: We demonstrate that undersowing annual clovers suppresses arable weeds and simultaneously support pollinators without reducing crop yields or taking land out of arable production. Undersown plant mixtures should, however, be tailored to support a wider spectrum of pollinators and benefit natural pest control to support a higher level of overall cropping system multi‐functionality. [ABSTRACT FROM AUTHOR]

In response to anthropogenic environmental change, the cues that animals use throughout their lifecycle to optimize fitness may become unreliable, resulting in an ecological trap.Here we investigated whether commercial bumble bee Bombus impatiens colonies managed for early spring crop pollination act as ecological traps for wild nest‐searching Bombus queens by subverting their natural nest usurpation behaviour.An average of 10 dead wild queens were recovered from each standard colony during the 2‐week period of the experiment, but colonies with queen excluders were successful in preventing wild queen deaths. The use of queen excluders did not impact colony performance in terms of resident queen survival, colony reproduction, colony weight gain or worker body size.Sites where wild nest‐searching queens were small had higher rates of failed usurpation, suggesting smaller‐sized queens are disproportionately at risk from failed usurpation. Furthermore, sites where commercial colonies without queen excluders were introduced for spring crop pollination had fewer bumble bee visits to a later‐blooming crop compared to sites without commercial colonies.Synthesis and applications. Our findings reveal a novel mechanism by which commercial colonies can negatively impact wild bumble bee populations and their pollination services. At the same time, we demonstrate a simple and inexpensive risk mitigation tool—a queen excluder—was 100% effective at eliminating this risk without compromising colony performance. Commercial colonies used outdoors during the bumble bee nest‐searching period should be fit with queen excluders to prevent negative impacts on wild pollinator communities and their services. [ABSTRACT FROM AUTHOR]

Bumblebees are important pollinators but are suffering from population declines due to land use intensification and climate change. In‐depth knowledge of species' relationships with different land use and climate variables is invaluable to guide conservation efforts, as well as enable predictions to be made about the impacts of future changes in these variables.Here we use 10 years of bumblebee abundance data from the UK, collected by citizen scientists as part of the BeeWalk scheme, to investigate associations between 14 bumblebee species and various land use, habitat and climate variables. National‐scale land cover and climate data were complemented with observer‐collected habitat data.Bumblebee presence and abundance showed strong relationships with environmental variables. However, interspecific variation was far stronger than commonalities, which suggests that targeted conservation work is required to effectively safeguard particular species. Within species, we found evidence of different habitat associations between reproductive and worker castes.The results also showed that wetland and riparian habitats had consistently positive associations with a number of species, while semi‐natural, arable and urban areas had strongly species‐specific associations.Synthesis and applications. This study reveals strong effects of specific habitats occurring within broad land cover types on the presence and abundance of bumblebees, with several distinct habitats having importance for different species and castes. Consequently, conservation efforts need to be carefully tailored to particular species. Nevertheless, reversing the loss of semi‐natural areas such as wetlands may be the single most generally effective action for bumblebee conservation while improving habitats in urban and arable areas could benefit particular (rare) species. Our results also suggest that the combination of long‐term, detailed monitoring data of both species and habitats, here collected by citizen scientists, with remotely sensed landcover and climate data is essential to extend knowledge of species' habitat requirements and to support future research and conservation. [ABSTRACT FROM AUTHOR]

Pollinating insects provide economic value by improving crop yield. They are also functionally and culturally important across ecosystems outside of cropland. To understand landscape‐level drivers of pollinator declines, and guide policy and intervention to reverse declines, studies must cover (a) multiple insect and plant taxa and (b) a range of agricultural and semi‐natural land uses. Furthermore, in an era of woodland restoration initiatives and rewilding ideologies, the contribution of woodland and woody linear features (WLFs; e.g. hedgerows) to pollinator abundance demands further investigation.We demonstrate fine‐scale analysis of high‐quality, co‐located measurements from a national environmental survey. We relate pollinator transect counts to ground‐truth habitat and WLF maps across 300 1 km squares in Wales, UK. We look at effects of habitat type, flower cover, WLF density and habitat diversity on summer abundance (July and August) of eight insect groups, representing three insect orders (Lepidoptera, Hymenoptera and Diptera).Compared with improved grassland (the dominant habitat in Wales), pollinator abundance is consistently higher in cropland and woodland—especially broadleaved woodland. For mining bees and two hoverfly groups, abundance is predicted to be at least 1.5× higher in woodland ecosystems than elsewhere. Furthermore, we estimate contributions of WLFs to abundance in agriculturally improved habitats to be up to 14% for honeybees and up to 21% for hoverflies.The abundance of all insect groups increases with flower cover, which is a key mechanism through which woodland, cropland and grassland support pollinators. Importantly, we observe diminishing returns of increasing flower cover for abundance of non‐Apis pollinator groups, expecting roughly twice the increase in abundance per % flower cover from 0% to 5%, as compared with 10% to 15%. However, the shape of the relationship was inverted for honeybees, which showed steeper increases in abundance at higher flower cover.Synthesis and applications. We provide a holistic view of the drivers of pollinator abundance in Wales, in which flower cover, woodland, hedgerows and cropland are critical. We propose a key role for woodland creation, hedge‐laying and farmland heterogeneity within future land management incentive schemes. Finally, we suggest targeting of interventions to maximise benefits for non‐Apis pollinators. Specifically, increasing floral provision in areas where existing flower cover is low—for example, in flower‐poor improved grasslands—could effectively increase pollinator abundance and diversity while prioritising wild over managed species. [ABSTRACT FROM AUTHOR]

In light of bee declines, the importance of pollination services from managed and native bees to our agriculture and economy is of great political, scientific and public interest. Viruses, first observed in honeybees, have been documented in bumblebees and the prevalence and load of some RNA viruses have been associated with managed honeybees. Shared flowers may be the bridge across which viruses pass between bees but no study has yet demonstrated that bumblebees can pick up viruses while foraging on contaminated flowers.Here, through a series of mechanistic laboratory experiments and mathematical modelling, we ask whether viruses can be transmitted between bee genera on shared flowers and how transmission can be effectively mitigated.We demonstrated that deformed wing virus (DWV) can be transmitted from infected honeybees to bumblebees through the use of shared red clover. We were also able to show that the route may work in reverse and bumblebees could contribute to the spread as well.Our model showed that reducing vector‐mediated transmission in honeybee colonies could potentially lead to a far greater reduction in bumblebee infection than simply reducing the number of honeybees. Additionally, we identified a dilution effect, whereby increasing floral abundance reduced transmission.Synthesis and applications. In this study, we showed that DWV may be spread between bee genera through the shared use of flowers. Through mathematical simulation, we identified two practical management options for reducing spread. The combination of treating honeybees effectively for the Varroa mite, a known vector of DWV, and increasing floral abundance where honeybees and native pollinators share the landscape were shown to reduce the spread of DWV within bee communities in simulations. [ABSTRACT FROM AUTHOR]

Populations of bumblebees and other pollinators have declined over the past several decades due to numerous threats, including habitat loss and degradation. However, we can rarely investigate the role of resource loss due to a lack of detailed long‐term records of forage plants and habitats.We used 22‐year repeated surveys of more than 262 sites located in grassland, forest, and wetland habitats across Illinois, USA to explore how the abundance and richness of bumblebee food plants have changed over the period of decline of the endangered rusty patched bumblebee Bombus affinis.We documented a decline in abundance of bumblebee forage plants in forest understories, which our phenology analysis suggests provide the primary nectar and pollen sources for foundress queens in spring, a critical life stage in bumblebee demography. By contrast, the per‐unit area abundance of food plants in primarily midsummer‐flowering grassland and wetland habitats had not declined. However, the total area of grasslands had declined across the region resulting in a net loss of grassland resources.Synthesis and applications. Our results suggest a decline in spring‐flowering forest understorey plants is a previously unappreciated bumblebee stressor, compounding factors like agricultural intensification, novel pathogen exposure and grassland habitat loss. These findings emphasize the need for greater consideration of habitat complementarity in bumblebee conservation. We conclude that the continued loss of early season floral resources may add additional stress to critical life stages of bumblebees and limit restoration efforts if not explicitly considered in pollinator conservation. [ABSTRACT FROM AUTHOR]

Effective weed control in agricultural crop fields increases yields, but simultaneously reduces floral resources for pollinators because many weed species provide pollen and nectar. Consequently, efforts to enhance crop yields on organic farms by using effective weed control methods risk compromising positive effects of organic farming on pollinating insects. Thus, it is important to find management strategies that alleviate the trade‐off between crop yields and flowering weeds on organic farms.We investigated the relationship between cereal yields, flowering weeds and bumblebees on organic and conventional arable land. We also investigated the potential of adjusting crop sowing density to benefit flowering weed species richness and floral resources to bumblebees without affecting crop yield.Floral resources and species richness of flowering weeds were higher in organic compared to conventional fields and were negatively related to crop yield in organic but not conventional fields (where the variation of floral resources and flowering weed species richness was comparatively low). Bumblebee species richness was higher in organic compared to conventional fields, and abundance was twice as high in organic as in conventional fields, but not significantly so. Yields in organic fields were two thirds of those in conventional fields. When simultaneously testing the effect of farming type (organic vs. conventional), crop yield and floral resources, only floral resources were related significantly to bumblebee abundance and species richness. A lower sowing density of the crop increased floral resources without negatively affecting crop yield.Synthesis and applications. We show that organic farming practices in cereals benefit bumblebees by allowing more flowering weeds, but at a cost in terms of lower yields. However, adjusting crop sowing density provides an opportunity to attain increased floral resources without negatively affecting crop yields. Thus, by increasing floral resources, adjusting crop sowing density may contribute to supporting high bumblebee densities, which in turn sustain pollination services to wild plants and insect‐pollinated crops, such as oilseed rape and field beans, in agricultural landscapes. We suggest that sowing strategies have the potential to contribute to ecological intensification by supporting organisms that provide ecosystem services to agriculture. [ABSTRACT FROM AUTHOR]

Pollinators underpin global food production, but they are suffering significant declines across the world. Pesticides are thought to be important drivers of these declines. Herbicides are the most widely applied type of pesticides and are broadly considered 'bee safe' by regulatory bodies who explicitly allow their application directly onto foraging bees. We aimed to test the mortality effects of spraying the world's most popular herbicide brand (Roundup®) directly onto bumble bees Bombus terrestris audax.We used three Roundup® products, the consumer products Roundup® Ready‐To‐Use and Roundup® No Glyphosate, the agricultural product Roundup® ProActive, as well as another herbicide with the same active ingredient (glyphosate), Weedol®. Label recommended pesticide concentrations were applied to the bees using a Roundup® Ready‐To‐Use spray bottle.Bees exhibited 94% mortality with Roundup® Ready‐To‐Use® and 30% mortality with Roundup® ProActive®, over 24 hr. Weedol® did not cause significant mortality, demonstrating that the active ingredient, glyphosate, is not the cause of the mortality. The 96% mortality caused by Roundup® No Glyphosate supports this conclusion. Dose‐dependent mortality caused by Roundup® Ready‐To‐Use, further confirms its acute toxicity. Roundup® products caused comprehensive matting of bee body hair, suggesting that surfactants, or other co‐formulants in the Roundup® products, may cause death by incapacitating the gas exchange system.These mortality results demonstrate that Roundup® products pose a significant hazard to bees, in both agricultural and urban systems, and that exposure of bees to them should be limited.Synthesis and applications. Surfactants, or other co‐formulants, in herbicides and other pesticides may contribute to global bee declines. We recommend that, as a precautionary measure until co‐formulant identities are made public, label guidelines for all pesticides be altered to explicitly prohibit application to plants when bees are likely to be foraging on them. As current regulatory topical exposure toxicity testing inadequately assesses toxicity of herbicide products, we call for pesticide companies to release the full list of ingredients for each pesticide formulation, as lack of access to this information hampers research to determine safe exposure levels for beneficial insects in agro‐ecosystems. [ABSTRACT FROM AUTHOR]

Floral resources are important in limiting pollinator populations, but they are often highly variable across time and space and the effect of this variation on pollinator population dynamics is not well understood. The phenology (timing) of floral resources is thought to be important in structuring pollinator populations, but few studies have directly investigated this.Our study quantifies the landscape composition, seasonal nectar and pollen supply and Bombus terrestris colony density of 12 farms in southwest UK to investigate how landscape composition influences the phenology of floral resources and how both these factors affect colony density. We use this information in a spatially explicit predictive model to estimate the effect of different farmland management scenarios on seasonal resource supplies and colony density.We find that farmland nectar supply during September is a strong predictor of B. terrestris colony density in the following year, explaining over half of all the variation in colony density; no other period of resource availability showed a significant association. Semi‐natural habitat cover was not a good proxy for nectar or pollen supply and showed no significant association with colony density. However, the proportional cover of gardens in the landscape was significantly associated with colony density.The predictive model results suggest that increasing the area of semi‐natural flowering habitat has limited effect on bumblebee populations. However, improving the quality of these habitats through Environmental Stewardship and other management options is predicted to reduce the late‐summer resource bottleneck and increase colony density.Synthesis and Applications. Our study demonstrates the importance of considering the phenology of resources, rather than just total resource availability, when designing measures to support pollinators. Late summer appears to be a resource bottleneck for bumblebees in UK farmland, and consequently management strategies which increase late‐summer nectar availability may be the most effective. These include mowing regimes to delay flowering of field margins until September, planting late‐flowering cover crops such as red clover and supporting late‐flowering wild plant species such as Hedera helix. Our results also suggest that rural gardens may play an important role in supporting farmland bumblebee populations. [ABSTRACT FROM AUTHOR]

Bumblebees are one of the most commonly studied pollinators, but they are declining in large parts of their distribution. Whether bumblebees can cope with anthropogenic disturbances such as climate change and habitat loss depends largely on their dispersal capacity. While bumblebee queen dispersal is estimated to be only a few kilometres, bird migration sites have documented mass‐migration events with peak migration of 70 bumblebee queens per minute, indicating that bumblebees can migrate over larger distances than previously thought.The open‐access database trektellen.org contains 10 daily counts of >1,000 migrating queens past single points in the Netherlands, and one in the United Kingdom (total bumblebee records 65,430; range 1–11,142 individuals), mostly in early spring. Such mass‐migration events are poorly documented in the scientific literature, and usually when describing migrations of other insects such as syrphids and social wasps.Most common European bumblebee species were documented to migrate. Bumblebees were observed flying at sea, coming from sea and flying towards the sea, showing that they can cross large water bodies. The wind direction might have helped to concentrate migration at landscape bottlenecks. On 1 day, bumblebee mass‐migration was documented on two sites located 200 km apart. Together with the concentrated and directional flight this suggests that they can migrate for several hundreds of kilometres.Because most mass‐migration events occur in spring, large‐scale shortage in suitable nesting sites may be the trigger for mass‐migration (e.g. due to high queen survival or low vole numbers). Future studies should test whether this is the case, or whether bumblebees show annual seasonal migration.Synthesis and applications. Much remains unclear about bumblebee migration, but it may have large consequences for the conservation of bumblebees and the ecosystem services they provide. For example, bumblebees in highly disturbed areas like agricultural landscapes may be continuously supplemented by queens from far‐away productive natural areas. This suggests that large‐scale conservation initiatives are required to maintain viable populations of common and endangered species. Structured observations and modern‐day technology, like isotope analyses or radar monitoring, may shed light on the drivers and consequences of the overlooked phenomenon of bumblebee migration. [ABSTRACT FROM AUTHOR]

Pollinators have experienced a dramatic decrease world‐wide due to agricultural intensification. In many countries, agri‐environment schemes (AES) have been introduced to counteract this current trend. However, until now, the relative importance of each AES for biodiversity and ecosystem services is still little understood and might change depending on landscape context. Complex landscape‐experiments are required to fill this knowledge gap, enabling the implementation of sustainable intensification of food production.In our study, we compared the effectiveness of the two most popular AES in Germany, organic farming and flower strips, in supporting pollinators and flower resources. We selected nine landscapes along a gradient of increasing field size, (configurational heterogeneity), each with a triplet of winter wheat fields: one organic, one conventional with flower strip and one conventional without flower strip as a control. We surveyed insect‐pollinated plants and pollinators (bumblebees, solitary bees and hoverflies). Additionally, we placed bumblebee colonies in the field edges to monitor their growth (colony weight gain) and reproduction (queen production).Flower strips stood out with the highest abundance and richness of pollinators. In contrast, bumblebee colony growth and plant richness benefited equally from organic and flower strip schemes. At the landscape scale, smaller fields had a positive effect on plant richness and bumblebee reproduction in flower strips. By contrast, bumblebee colonies in organic agriculture benefited most from large fields, as large organic fields provided much more flower resources than the narrow flower strips.Synthesis and applications. Our results showed that both local and landscape management shaped pollinator communities and their reproduction. Overall, organic farming and flower strips appeared to be effective tools to mitigate flower shortage in conventional cereal fields, with organic farming supporting the highest flowering plant cover per field. Flower strips enhanced local pollinator richness most, but increased bumblebee reproduction only when the surrounding landscapes had small fields with long field borders. Therefore, our results reveal that European Union policies need to take into account that the effectiveness of agri‐environment schemes depends on the structure of the surrounding landscape. [ABSTRACT FROM AUTHOR]

Climate change has been commonly associated with a decline of bumblebee populations around the world. However, most information regarding the impacts of climate change on bumblebees is derived from North America and Europe, and little is known about South American species.Here we applied ecological niche modelling techniques to estimate the past, present and future distributions of six Bombus species found in South America. These data were used to estimate climatically stable areas (CSAs) for each species and, combined with information on land cover and protected area network, identify species and areas for the conservation of these important pollinators.The models predicted a reduction in climatically suitable habitats from Last Glacial Maximum (LGM) to the present for most species. Similarly, all species were predicted to lose climatically suitable areas in future climate scenarios, ranging from 9% to 78%, depending on the species and climate change scenario.The percentage of legally protected CSAs varied between 4.0% and 48.2% among species, mainly due to differences in the protected area network among the biomes in which they occur. A significant portion of the distribution range of most species includes agricultural areas, which likely increases bumblebee exposure to pesticides.Based on the estimated habitat loss due to climate change, as well as from land cover and protected area, our results indicate that Bombus bellicosus, Bombus brevivillus and Bombus brasiliensis are the most endangered species of those evaluated.Synthesis and applications. Our findings provide a framework for conservation strategies of six species of South American bumblebees, by prioritizing species and areas for conservation considering their distribution range and the climatically stable areas under different climate change scenarios. [ABSTRACT FROM AUTHOR]

Post‐industrial shrinking cities contain abundant vacant land and are increasingly recognized for their pollinator conservation potential. At the same time, the industrial legacies of these urban ecosystems have resulted in elevated levels of heavy metals in surface soils, which could negatively affect bee populations.We investigated whether foraging within heavy metal contaminated landscapes represents a fitness cost for the common Eastern bumblebee Bombus impatiens, by placing colonies in residential backyards along an urban to rural gradient extending south and east from the city of Cleveland, Ohio, USA. Bees foraged in the landscape for 3 weeks, after which time we counted the total number of workers and larvae present in the colony and analysed castes for the presence of heavy metals. We then assessed the relationship between landscape composition, heavy metal loads and caste abundance.Colonies located in urban landscapes were more likely to be exposed to lead (Pb). Elevated concentrations of Pb within workers were negatively correlated with both the number of workers and the number of larvae present.Synthesis and applications. Our findings raise concern that lead (Pb) contamination could represent a significant challenge to bee conservation in cities. To elucidate risks posed by this pollutant, we highlight a need to quantify lethal and sub‐lethal effects of Pb exposure using laboratory and field‐based studies. Further, identifying routes of exposure and landscape factors that influence exposure risk is necessary to implement mitigation strategies as part of urban conservation initiatives. [ABSTRACT FROM AUTHOR]

Agricultural intensification and associated loss of high‐quality habitats are key drivers of insect pollinator declines. With the aim of decreasing the environmental impact of agriculture, the 2014 EU Common Agricultural Policy (CAP) defined a set of habitat and landscape features (Ecological Focus Areas: EFAs) farmers could select from as a requirement to receive basic farm payments. To inform the post‐2020 CAP, we performed a European‐scale evaluation to determine how different EFA options vary in their potential to support insect pollinators under standard and pollinator‐friendly management, as well as the extent of farmer uptake.A structured Delphi elicitation process engaged 22 experts from 18 European countries to evaluate EFAs options. By considering life cycle requirements of key pollinating taxa (i.e. bumble bees, solitary bees and hoverflies), each option was evaluated for its potential to provide forage, bee nesting sites and hoverfly larval resources.EFA options varied substantially in the resources they were perceived to provide and their effectiveness varied geographically and temporally. For example, field margins provide relatively good forage throughout the season in Southern and Eastern Europe but lacked early‐season forage in Northern and Western Europe. Under standard management, no single EFA option achieved high scores across resource categories and a scarcity of late season forage was perceived.Experts identified substantial opportunities to improve habitat quality by adopting pollinator‐friendly management. Improving management alone was, however, unlikely to ensure that all pollinator resource requirements were met. Our analyses suggest that a combination of poor management, differences in the inherent pollinator habitat quality and uptake bias towards catch crops and nitrogen‐fixing crops severely limit the potential of EFAs to support pollinators in European agricultural landscapes.Policy Implications. To conserve pollinators and help protect pollination services, our expert elicitation highlights the need to create a variety of interconnected, well‐managed habitats that complement each other in the resources they offer. To achieve this the Common Agricultural Policy post‐2020 should take a holistic view to implementation that integrates the different delivery vehicles aimed at protecting biodiversity (e.g. enhanced conditionality, eco‐schemes and agri‐environment and climate measures). To improve habitat quality we recommend an effective monitoring framework with target‐orientated indicators and to facilitate the spatial targeting of options collaboration between land managers should be incentivised. [ABSTRACT FROM AUTHOR]

The alarming loss of pollinator diversity world‐wide can reduce the productivity of pollinator‐dependent crops, which could have economic impacts. However, it is unclear to what extent the loss of a key native pollinator species affects crop production and farmer's profits.By experimentally manipulating the presence of colonies of a native bumblebee species Bombus pauloensis in eight apple orchards in South Argentina, we evaluated the impact of losing natural populations of a key native pollinator group on (a) crop yield, (b) pollination quality, and (c) farmer's profit. To do so, we performed a factorial experiment of pollinator exclusion (yes/no) and hand pollination (yes/no).Our results showed that biotic pollination increased ripe fruit set by 13% when compared to non‐biotic pollination. Additionally, fruit set and the number of fruits per apple tree was reduced by less than a half in those orchards where bumblebees were absent, even when honeybees were present at high densities. Consequently, farmer's profit was 2.4‐fold lower in farms lacking bumblebees than in farms hosting both pollinator species. The pollination experiment further suggested that the benefits of bumblebees could be mediated by improved pollen quality rather than quantity.Synthesis and applications. This study highlights the pervasive consequences of losing key pollinator functional groups, such as bumblebees, for apple production and local economies. Adopting pollinator‐friendly practices such as minimizing the use of synthetic inputs or restoring/maintaining semi‐natural habitats at farm and landscape scales, will have the double advantage of promoting biodiversity conservation, and increasing crop productivity and profitability for local farmers. Yet because the implementation of these practices can take time to deliver results, the management of native pollinator species can be a provisional complementary strategy to increase economic profitability of apple growers in the short term. [ABSTRACT FROM AUTHOR]

Sulfoximine‐based insecticides, such as sulfoxaflor, are of increasing global importance and have been registered for use in 81 countries, offering a potential alternative to neonicotinoid insecticides.Previous studies have demonstrated that sulfoxaflor exposure can have a negative impact on the reproductive output of bumblebee colonies, but the specific life‐history variables that underlie these effects remain unknown.Here, we used a microcolony‐based protocol to assess the sub‐lethal effects of chronic sulfoxaflor exposure on egg laying, larval production, ovary development, sucrose consumption, and mortality in bumblebees. Following a pre‐registered design, we exposed colonies to sucrose solutions containing 0, 5, 10 and 250ppb of sulfoxaflor. Exposure at 5 ppb has been previously shown to negatively impact colony reproductive success.Our results showed that sulfoxaflor exposure at 5 ppb (lowest exposure tested) reduced the number of eggs found within the microcolonies (Hedge's d = −0.37), with exposed microcolonies also less likely to produce larvae (Hedge's d = −0.36). Despite this, we found no effect of sulfoxaflor exposure on ovarian development. Sulfoxaflor‐exposed bumblebees consumed less sucrose solution, potentially driving the observed reduction in egg laying.Policy implications. Regulatory bodies such as the European Food Safety Authority (EFSA) are under increasing pressure to consider the potential impact of insecticides on wild bees, such as bumblebees, but sublethal effects can go undetected at lower‐tier testing. In identifying just such an effect for bumblebees exposed to sulfoxaflor, this study highlights that microcolony‐based protocols are a useful tool that could be implemented within an ecotoxicology framework. Furthermore, the results provide evidence for potentially negative consequences of pollinator exposure to an insecticide that is currently undergoing the licensing process in several EU member states. [ABSTRACT FROM AUTHOR]

Floral resources are known to be important in regulating wild pollinator populations and are therefore an important component of agri‐environment and restoration schemes which aim to support pollinators and their associated services. However, the phenology of floral resources is often overlooked in these schemes — a factor which may be limiting their success.Our study characterizes and quantifies the phenology of nectar resources at the whole‐farm scale on replicate farms in Southwestern UK throughout the flowering season. We quantify the corresponding nectar demands of a subset of common wild pollinators (bumblebees) to compare nectar supply and pollinator demand throughout the year, thereby identifying periods of supply‐demand deficit.We record strong seasonal fluctuations in farmland nectar supplies, with two main peaks of nectar production (May and July) and a considerable "June Gap" in between. March and August/September are also periods of low nectar availability.Comparing the phenology of nectar supply with the phenology of bumblebee nectar demand reveals "hunger gaps" during March and much of August/September when supply is unlikely to meet demand.Permanent pasture and woodland produced the greatest share of farmland nectar because of their large area; however, linear features such as hedgerows and field margins provided the greatest nectar per unit area. Fifty percent of total nectar was supplied by just three species (Allium ursinum, Cirsium arvense and Trifolium repens), but some less productive species (e.g. Hedera helix and Taraxacum agg.) were important in ensuring phenological continuity of nectar supply.Synthesis and applications. By comparing the phenology of farmland nectar supply with the phenology of pollinator demand, we demonstrate that the timing of nectar supply may be as important as total nectar production in limiting farmland pollinator populations. Considering phenology in the design of agri‐environment or restoration schemes is therefore likely to improve their suitability for pollinators. Plant species which flower during periods of resource deficit (early spring and late summer) should be prioritized in schemes which aim to conserve or restore pollinator populations. Maintaining a range of semi‐natural habitats with complementary flowering phenologies (e.g. woodland, hedgerows and field margins) will ensure a more continuous supply of nectar on farmland, thereby supporting pollinators for their entire flight season. By comparing the phenology of farmland nectar supply with the phenology of pollinator demand, we demonstrate that the timing of nectar supply may be as important as total nectar production in limiting farmland pollinator populations. Considering phenology in the design of agri‐environment or restoration schemes is therefore likely to improve their suitability for pollinators. Plant species which flower during periods of resource deficit (early spring and late summer) should be prioritized in schemes which aim to conserve or restore pollinator populations. Maintaining a range of semi‐natural habitats with complementary flowering phenologies (e.g. woodland, hedgerows and field margins) will ensure a more continuous supply of nectar on farmland, thereby supporting pollinators for their entire flight season. [ABSTRACT FROM AUTHOR]

In early spring when farmland nectar is scarce, dandelions are a salvation for hungry queen bumblebees (pp, 1006-1016). Photo: © Tom Timberlake. [Extracted from the article]

Bumblebees are important pollinators for a wide range of crops and wild plants. Performance of their colonies depends on pollen and nectar as food resources, but flowering plants are scarce in modern agricultural landscapes. It is well‐known that semi‐natural habitats can enhance floral resources and bumblebee abundance, but the impact of different crop types and their heterogeneity at the landscape scale remains unclear.We tested the effect of two different crop types (oilseed rape [OSR] and maize) and of configurational (field border density) and compositional heterogeneity (crop diversity) on weight gain of buff‐tailed bumblebee colonies (Bombus terrestris) and the pollen diversity collected by them in 20 landscapes in Central Germany.We found that augmenting maize cover had a detrimental effect on pollen diversity collected by bumblebees, probably due to intensive management resulting in low plant diversity. This low pollen diversity translated into reduced colony growth, since colonies with high pollen diversity gained more weight than colonies with low pollen diversity.In contrast, OSR cover and configurational and compositional heterogeneity did neither affect colony growth nor pollen diversity. However, for OSR, the timing of the flowering period was important. When OSR fields had a high flower cover at the end of the OSR blooming period, colonies showed increased growth rates.Synthesis and applications. Our results complement previous laboratory studies by showing that high pollen diversity leads to better colony performance under field conditions. Therefore, the maintenance of floral diversity in agricultural landscapes is crucial to ensure that bumblebees can fulfil their nutritional needs. However, the heterogeneity of crops, at least under the currently very low levels of crop rotation, does not contribute to this aim. In contrast, crop identity and timing of mass‐flowering crops turned out to be important factors, as maize reduced pollen resources, while late blooming oilseed rape (OSR) was beneficial to bumblebee colonies. Hence, maize cover per landscape should be reduced and strategies to enhance landscape wide flower diversity, especially towards and after the end of oilseed rape bloom, should be promoted to support bumblebee colonies that provide important pollination services. Our results complement previous laboratory studies by showing that high pollen diversity leads to better colony performance under field conditions. Therefore, the maintenance of floral diversity in agricultural landscapes is crucial to ensure that bumblebees can fulfil their nutritional needs. However, the heterogeneity of crops, at least under the currently very low levels of crop rotation, does not contribute to this aim. In contrast, crop identity and timing of mass‐flowering crops turned out to be important factors, as maize reduced pollen resources, while late blooming oilseed rape (OSR) was beneficial to bumblebee colonies. Hence, maize cover per landscape should be reduced and strategies to enhance landscape wide flower diversity, especially towards and after the end of oilseed rape bloom, should be promoted to support bumblebee colonies that provide important pollination services. [ABSTRACT FROM AUTHOR]

The global trade of species promotes diverse human activities but also facilitates the introduction of potentially invasive species into new environments. As species ignore national boundaries, unilateral national decisions concerning species trade set the stage for transnational species invasion with significant conservation, economic and political consequences.The need for a coordinated approach to species importation policies is demonstrated by the introduction of two bumblebee species into Chile for crop pollination, despite Argentina banning commercial importation of alien bumblebees based on expert opinion. The large garden bumblebee, Bombus ruderatus, was first introduced in 1982, and the buff‐tailed bumblebee, Bombus terrestris, has been continually introduced since 1997 as part of the burgeoning bumblebee trade. Both species have subsequently invaded southern South America. Today, the consequences of the growth of the bumblebee trade for agricultural pollination ranks among the top 15 emerging environmental issues likely to affect global diversity.Documented impacts of these invasions include the severe decline and local extinctions of the sole native Patagonian bumblebee, Bombus dahlbomii, pathogen transmission, flower damage and nectar robbing of native and cultivated plants.Policy implications. The South American bumblebee invasions portrayed here should alert governments to the unintended consequences of the booming international bee trade. More broadly, this case demonstrates that one country's importation decisions can have policy implications for its neighbours without consultation. Regrettably, coordinated international measures to prevent species invasions are seldom considered in South America or elsewhere, despite existing legal frameworks. The bumblebee case and others provide stark evidence of the pressing need for coordinated specific and general international policies concerning global species trade and their implementation. [ABSTRACT FROM AUTHOR]

Bumblebees inhabit spatially heterogeneous landscapes that are likely characterized by population sources and sinks. To date, most studies of bumblebee habitat requirements have examined static relationships between worker abundance and habitat characteristics. However, if habitat types are linked by dispersal, source‐sink dynamics could alter overall population sensitivity to habitat loss, changing conclusions from static approaches.Here, we used empirically derived spatial matrix models to study source‐sink population dynamics of bumblebees in heterogeneous environments. We used these models to assess population sensitivity to habitat loss and to examine the population dynamics that could occur under rapid habitat change.Loss of natural habitat reduced long‐term population growth rates, and more natural habitat was required to sustain bumblebee species with long‐distance dispersal than species with short‐distance dispersal. The long‐term relative density of colonies in each habitat type depended on landscape structure and bumblebee dispersal ability. Under most conditions, high‐quality habitat contained higher densities of colonies than low‐quality habitats. However, low‐quality habitat could contain higher densities than high‐quality habitats if populations were in long‐term decline.Rapid loss or restoration of natural habitat produced transient population dynamics that differed from long‐term dynamics. After large landscape perturbations that affected population structure, transient dynamics persisted for 4–8 years and were longest for species with short dispersal in highly aggregated landscapes. While transient dynamics were short in duration, they caused large effects on long‐term population density.Synthesis and applications. When habitats are linked by dispersal or populations have recently experienced perturbations, patterns of abundance on the landscape may not reflect variation in habitat quality. Spatially structured matrix population models are practical tools than can be used to account for nonequilibrium and source‐sink dynamics. For bumblebees, population sensitivity to habitat loss and the duration of transient dynamics depend on dispersal ability and landscape configuration. Demographic approaches such as ours can help to disentangle population patterns from processes and will therefore be valuable for guiding conservation and management. When habitats are linked by dispersal or populations have recently experienced perturbations, patterns of abundance on the landscape may not reflect variation in habitat quality. Spatially structured matrix population models are practical tools than can be used to account for nonequilibrium and source‐sink dynamics. For bumblebees, population sensitivity to habitat loss and the duration of transient dynamics depend on dispersal ability and landscape configuration. Demographic approaches such as ours can help to disentangle population patterns from processes and will therefore be valuable for guiding conservation and management. [ABSTRACT FROM AUTHOR]

World‐wide declines in pollinators, including bumblebees, are attributed to a multitude of stressors such as habitat loss, resource availability, emerging viruses and parasites, exposure to pesticides, and climate change, operating at various spatial and temporal scales. Disentangling individual and interacting effects of these stressors, and understanding their impact at the individual, colony and population level are a challenge for systems ecology. Empirical testing of all combinations and contexts is not feasible. A mechanistic multilevel systems model (individual‐colony‐population‐community) is required to explore resilience mechanisms of populations and communities under stress.We present a model which can simulate the growth, behaviour and survival of six UK bumblebee species living in any mapped landscape. Bumble‐BEEHAVE simulates, in an agent‐based approach, the colony development of bumblebees in a realistic landscape to study how multiple stressors affect bee numbers and population dynamics. We provide extensive documentation, including sensitivity analysis and validation, based on data from literature. The model is freely available, has flexible settings and includes a user manual to ensure it can be used by researchers, farmers, policy‐makers, NGOs or other interested parties.Model outcomes compare well with empirical data for individual foraging behaviour, colony growth and reproduction, and estimated nest densities.Simulating the impact of reproductive depression caused by pesticide exposure shows that the complex feedback mechanisms captured in this model predict higher colony resilience to stress than suggested by a previous, simpler model.Synthesis and applications. The Bumble‐BEEHAVE model represents a significant step towards predicting bumblebee population dynamics in a spatially explicit way. It enables researchers to understand the individual and interacting effects of the multiple stressors affecting bumblebee survival and the feedback mechanisms that may buffer a colony against environmental stress, or indeed lead to spiralling colony collapse. The model can be used to aid the design of field experiments, for risk assessments, to inform conservation and farming decisions and for assigning bespoke management recommendations at a landscape scale. The Bumble‐BEEHAVE model represents a significant step towards predicting bumblebee population dynamics in a spatially explicit way. It enables researchers to understand the individual and interacting effects of the multiple stressors affecting bumblebee survival and the feedback mechanisms that may buffer a colony against environmental stress, or indeed lead to spiralling colony collapse. The model can be used to aid the design of field experiments, for risk assessments, to inform conservation and farming decisions and for assigning bespoke management recommendations at a landscape scale. [ABSTRACT FROM AUTHOR]

Abstract: In many parts of the world, farmland pollinators decreased significantly during the last half of the 20th century mainly due to land‐use changes and agricultural intensification. We studied the effect of different typical crop rotations and agri‐environment schemes (AES) on bumblebee diversity in Estonia. We compared species abundances between four crop rotation types (cereal rollover [no change from 1 year to the next], cereal to mass‐flowering crops [hereafter MFC], MFC rollover and MFC to cereal fields) where all counts were conducted in the second year and in three farming types (conventional farming, organic farming and environmentally friendly management). We surveyed bumblebees and flower cover along 401 field margins in five consecutive years and recorded 20 species and more than 6,000 individuals. Abundances of long‐tongued and threatened bumblebee species were higher at the field margins of cereal rollover fields than for the other three crop rotation types. In addition, cereal rollover field margins had higher abundances of medium colony species, generalists and forest‐scrub species than MFC rollover and MFC to cereal or cereal to MFC field margins. Bumblebee species richness was higher at the field margins of both AES types than those of conventional farming. However, in general, the strongest driver of bumblebee presence was flower cover. Higher bumblebee abundances in cereal rollover field margins were probably owing to a concentration effect there and/or a dilution effect into MFC fields. Both AES schemes supported increasing flower cover in field margins and thereby diversity of bumblebees, indicating positive AES impacts upon wild pollinators. Synthesis and applications. Crop rotation and agri‐environment schemes determine bumblebee richness and abundance via the availability of flower resources, but crop rotation constrains bumblebees differently based on their traits. Therefore, future agri‐environmental policy should account for these management options. Crop rotation could be a simple, but efficient solution to increase the biodiversity of agricultural landscapes. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Honeybees have world-wide importance as crop pollinators. To ensure their persistence in agricultural systems, statistically robust field trials of plant protection products are vital., We consider the implications of regulations from the European Food Safety Authority that require the detection of a 7% effect size change in bee colony sizes under field conditions., Based on a power analysis, we argue that the necessary levels of replication (68 replicates) may pose practical constraints to field testing., Policy implications. Regulatory studies benefit from data sources collated over a range of spatial scales, from laboratory to landscapes. Basing effect size thresholds solely on expert judgement, as has been done, may be inappropriate. Rather, definition through experimental or simulation studies that assess the biological consequences of changes in colony size for bee populations is required. This has implications for regulatory bodies outside the European Union. [ABSTRACT FROM AUTHOR]

The ability to forage and return home is essential to the success of bees as both foragers and pollinators. Pesticide exposure may cause behavioural changes that interfere with these processes, with consequences for colony persistence and delivery of pollination services., We investigated the impact of chronic exposure (5-43 days) to field-realistic levels of a neonicotinoid insecticide (2·4 ppb thiamethoxam) on foraging ability, homing success and colony size using radio frequency identification ( RFID) technology in free-flying bumblebee colonies., Individual foragers from pesticide-exposed colonies carried out longer foraging bouts than untreated controls (68 vs. 55 min). Pesticide-exposed bees also brought back pollen less frequently than controls indicating reduced foraging performance., A higher proportion of bees from pesticide-exposed colonies returned when released 1 km from their nests; this is potentially related to increased orientation experience during longer foraging bouts. We measured no impact of pesticide exposure on homing ability for bees released from 2 km, or when data were analysed overall., Despite a trend for control colonies to produce more new workers earlier, we found no overall impacts of pesticide exposure on whole colony size., Synthesis and applications. This study shows that field-realistic neonicotinoid exposure can have impacts on both foraging ability and homing success of bumblebees, with implications for the success of bumblebee colonies in agricultural landscapes and their ability to deliver crucial pollination services. Pesticide risk assessments should include bee species other than honeybees and assess a range of behaviours to elucidate the impact of sublethal effects. This has relevance for reviews of neonicotinoid risk assessment and usage policy world-wide. [ABSTRACT FROM AUTHOR]

Domestic gardens typically consist of a mixture of native and non-native plants which support biodiversity and provide valuable ecosystem services, particularly in urban environments. Many gardeners wish to encourage biodiversity by choosing appropriate plant taxa. The value of native and non-native plants in supporting animal biodiversity is, however, largely unknown., The relative value of native and non-native garden plants to invertebrates was investigated in a replicated field experiment. Plots (deliberately akin to garden borders) were planted with one of three treatments, representing assemblages of plants based on origin (native, near-native and exotic). Invertebrates and resource measurements were recorded over four years. This paper reports the abundance of flower-visiting aerial insects ('pollinators') associated with the three plant assemblages., For all pollinator groups on all treatments, greater floral resource resulted in an increase in visits. There was, however, a greater abundance of total pollinators recorded on native and near-native treatments compared with the exotic plots. Short-tongued bumblebees followed the same pattern whilst more hoverflies were recorded on the native treatment than the other treatments, and more honeybees on the near-native treatment. There was no difference between treatments in abundance of long-tongued bumblebees or solitary bees. The lack of difference in solitary bee abundance between treatments was probably due to a third of individuals from this group being recorded on one exotic plant species., The number of flower visitors corresponded to the peak flowering period of the treatments, that is there were fewer flower visitors to the exotic treatment compared with the other treatments in early summer but relatively more later in the season., Synthesis and applications. This experiment has demonstrated that utilizing plants from only a single region of origin (i.e. nativeness) may not be an optimal strategy for resource provision for pollinating insects in gardens. Gardens can be enhanced as a habitat by planting a variety of flowering plants, biased towards native and near-native species but with a selection of exotics to extend the flowering season and potentially provide resources for specialist groups. [ABSTRACT FROM AUTHOR]

Agri-environment schemes remain a controversial approach to reversing biodiversity losses, partly because the drivers of variation in outcomes are poorly understood. In particular, there is a lack of studies that consider both social and ecological factors., We analysed variation across 48 farms in the quality and biodiversity outcomes of agri-environmental habitats designed to provide pollen and nectar for bumblebees and butterflies or winter seed for birds. We used interviews and ecological surveys to gather data on farmer experience and understanding of agri-environment schemes, and local and landscape environmental factors., Multimodel inference indicated social factors had a strong impact on outcomes and that farmer experiential learning was a key process. The quality of the created habitat was affected positively by the farmer's previous experience in environmental management. The farmer's confidence in their ability to carry out the required management was negatively related to the provision of floral resources. Farmers with more wildlife-friendly motivations tended to produce more floral resources, but fewer seed resources., Bird, bumblebee and butterfly biodiversity responses were strongly affected by the quantity of seed or floral resources. Shelter enhanced biodiversity, directly increased floral resources and decreased seed yield. Seasonal weather patterns had large effects on both measures. Surprisingly, larger species pools and amounts of semi-natural habitat in the surrounding landscape had negative effects on biodiversity, which may indicate use by fauna of alternative foraging resources., Synthesis and application. This is the first study to show a direct role of farmer social variables on the success of agri-environment schemes in supporting farmland biodiversity. It suggests that farmers are not simply implementing agri-environment options, but are learning and improving outcomes by doing so. Better engagement with farmers and working with farmers who have a history of environmental management may therefore enhance success. The importance of a number of environmental factors may explain why agri-environment outcomes are variable, and suggests some - such as the weather - cannot be controlled. Others, such as shelter, could be incorporated into agri-environment prescriptions. The role of landscape factors remains complex and currently eludes simple conclusions about large-scale targeting of schemes. [ABSTRACT FROM AUTHOR]

Reductions in natural habitat are implicated in declining honeybee Apis mellifera L. and wild bee populations, thereby threatening crop production. This concern has stimulated interest in identifying landscape-level impacts on bee-mediated pollination services, but previous studies have only inferred connections between landscape, bees and yield through generalized linear regressions., We examined landscape impacts on bee-mediated crop yield using both a traditional linear regression approach and conditional process modelling, which combined landscape features, bee visits to crop flowers, and the interactions between landscape and bee visits to flowers into a single model predicting crop yield. We used the pumpkin Cucurbita pepo L. system in New York State and recorded bees visiting pumpkin flowers in 2011 and 2012. Landscape diversity and percentage of semi-natural grassland around each pumpkin field were calculated., Results from the traditional approach indicated that landscape diversity, percentage of grassland in the landscape, bumblebee Bombus impatiens Cresson and honeybee visitation frequency each positively predicted yield. A common conclusion from these results is that pumpkins grown in highly diverse or high grassland coverage landscapes would have greater yields via bumblebee and honeybee visits to flowers. However, this inference does not preclude the possibility that landscape features may be associated with crop yield, independent of bee visits to flowers., Results from conditional process modelling indicated that only pumpkins grown in highly diverse landscapes were predicted to have greater yields as a consequence of more bumblebee visits to pumpkin flowers. None of the landscape features predicted greater fruit yields as a consequence of more honeybee visits to pumpkin flowers. This novel analysis indicated that traditional approaches may be misinterpreting the relationships between these variables., Synthesis and applications. Bumblebees benefited from a diverse landscape, and their visits to flowers positively impacted pumpkin production. Conservation of a diverse landscape should be promoted to support improved pumpkin production. Growers can use this information to decide where to plant pumpkins to improve the potential for high yields, to identify scenarios where landscape diversity could be increased, and where supplementation with bees might be beneficial. [ABSTRACT FROM AUTHOR]

Pollinating insects provide vital ecosystem services of enormous importance for economies and biodiversity. Yet, there is a concerning global trend of pollinator declines. Parasites and pesticides are among the suspected principle drivers of these declines. However, especially in the case of key wild pollinators, there are insufficient data on the relative impact of these individual environmental stressors and whether they interact to increase detrimental effects., Using a fully crossed factorial design, we investigated how laboratory exposure to neonicotinoid insecticides, thiamethoxam and clothianidin, over a 9-week period and a prevalent trypanosome gut parasite Crithidia bombi affects various crucial colony traits of the bumblebee Bombus terrestris., We show that chronic dietary exposure from an early stage of colony development to doses of thiamethoxam and clothianidin that could be encountered in the field truncated worker production, reduced worker longevity and decreased overall colony reproductive success. Further, we demonstrate a significant interaction between neonicotinoid exposure and parasite infection on mother queen survival. The fate of the mother queen is intrinsically linked to colony success, and under combined pressure of parasite infection and neonicotinoid exposure, mother queen survival was lowest. This indicates increased detrimental effects of combined exposure on this crucial colony trait. Combined effects may be exacerbated in stressful natural environments where more pronounced parasite virulence is expected., Synthesis and applications. Our findings reiterate that dietary exposure to neonicotinoids can impact on bumblebee colony performance and fitness. The indication of combined negative effects of ecologically relevant pressures suggests additional adverse consequences for long-term population dynamics under complex field conditions. To help safeguard pollinator health, whole life-cycle fitness assessments, particularly for non- Apis bees, stringently incorporating chronic and sublethal side effects of pesticides, as well as interactions with common natural stressors, such as prevalent parasites, should be considered in the corresponding test guidelines. [ABSTRACT FROM AUTHOR]

Bees are exposed to pesticides when foraging in agricultural areas and growing evidence suggests that such compounds can be harmful to managed and wild populations. Given the economic and ecological importance of bees, and the evidence of widespread population declines, the full impacts of pesticides and their interactions with other stressors in the environment need to be investigated., Here, we focus on the impacts of chronic exposure to the commonly used pyrethroid pesticide lambda (λ)-cyhalothrin on the bumblebee Bombus terrestris at both the individual and colony level. Furthermore, we investigated the interactions of pesticide exposure with a highly prevalent trypanosome parasite Crithidia bombi. Colonies were exposed to λ-cyhalothrin in the laboratory, and colony growth and reproductive output were monitored for up to 14 weeks. The potential interactions between the pesticide and C. bombi were investigated by quantifying the impact of pesticide treatment on susceptibility to, and success of experimental infections, as well as the survival of workers. Male survival after larval pesticide exposure was also monitored., Pesticide-treated colonies produced workers with a significantly lower body mass. However, out of the twelve variables of colony development measured, this was the only metric that was significantly affected by pesticide treatment and there was no subsequent significant impact on the reproductive output of colonies., Lambda-cyhalothrin had no significant impact on the susceptibility of workers to C. bombi, or intensity of parasitic infection., Pesticide exposure did not cause differential survival in workers or males, even when workers were additionally challenged with C. bombi., Synthesis and applications. Chronic exposure to λ-cyhalothrin has a significant impact on worker size, a key aspect of bumblebee colony function, particularly under conditions of limited food resources. This could indicate that under times of resource limitation, colonies exposed to this pesticide in the field may fail. However, the lack of other impacts found in this study indicate that further field trials are needed to elucidate this. [ABSTRACT FROM AUTHOR]

Over a million commercially produced bumblebee colonies are imported annually on a global scale for the pollination of greenhouse crops. After importation, they interact with other pollinators, with an associated risk of any parasites they carry infecting and harming native bees. National and supranational regulations are designed to prevent this, and commercially produced bumblebee colonies are accordingly now often sold and imported as being parasite-free., Here, we used molecular methods to examine the occurrence of parasites in bumblebee colonies that were commercially produced in 2011 and 2012 by three producers. We then used controlled experiments to determine whether any parasites present were infectious., We found that 77% of the commercially produced bumblebee colonies from the three producers, which were imported on the basis of being free of parasites, in fact carried microbial parasites, with five different parasites being detected across the total sample of bumblebees and a further three in the pollen supplied with the colonies as food., Our controlled experiments demonstrated that at least three of these parasites were infectious to bumblebees with significant negative effects on their health. Furthermore, we also found that at least four of the parasites carried by commercially produced bumblebees were infectious to honeybees, indicating that they pose a risk to other pollinators as well., Synthesis and applications. The results demonstrate that commercially produced bumblebee colonies carry multiple, infectious parasites that pose a significant risk to other native and managed pollinators. More effective disease detection and management strategies are urgently needed to reduce the pathogen spillover threat from commercially produced bumblebees. [ABSTRACT FROM AUTHOR]

Global declines in pollinating insects have been linked with agricultural intensification and land-use change. Increased production of novel crops for bioenergy is causing changes in agricultural practice, but the effects on different pollinating taxa have not yet been quantified. However, the major pollinating groups (social bees, solitary bees, hoverflies and butterflies) are likely to respond differently to changes in land use and shifts in crop cultivation patterns., We assessed the impacts of two bioenergy crops, oilseed rape Brassica napus L. and Miscanthus Miscanthus X giganteus on (i) the diversity and abundance of four taxonomic groups of pollinating insects, (ii) insect community composition, (iii) floral resources and (iv) nesting sites for bumblebees, by comparing bioenergy crops with conventional arable and grass crops in a large network of commercial fields., We found that although there were more bumblebees in oilseed rape fields, conventional crops and bioenergy crops did not differ greatly in species richness of most pollinator groups, although more floral resources were found in the bioenergy crops. However, solitary bees were more abundant and species rich in energy crops than conventional wheat, and more trap-nesting bees and wasps were found in Miscanthus than oilseed rape. In addition, novel assemblages of solitary bees were found in the bioenergy crops., All pollinator groups, and flowering plants, were more abundant in field margins than in the centre of crop fields. Although there were no differences among crop types, nest-searching bumblebees were confined to field margins. This highlights the importance of field margins as forage and nesting habitat for pollinators in farmland., Synthesis and applications. Differential responses to field-scale growth of bioenergy crops were displayed by the taxonomic groups studied, suggesting that effects on biodiversity cannot be generalized from studies based on a small suite of taxonomic groups and must include a range of taxa for overarching results. To optimize habitat for pollinators in agricultural areas, our data suggest that a diversity of crop types at small scales may have positive impacts and supports appropriate management and conservation of field margins and hedgerows during conversion to bioenergy production. [ABSTRACT FROM AUTHOR]

Summary 1. Establishing temporal habitat patches, such as long-term set-aside, is potentially a valuable approach to support pollinator populations in intensively cultivated landscapes. The benefits of this approach are expected to differ between pollinator groups, because of fundamental differences in their ecology. 2. We studied the responses of two pollinator groups, bumblebees and diurnal Lepidoptera (butterflies and diurnal moths), to the vegetation succession in experimental set-aside during six consecutive years. The pollinators were monitored in 24 large treatment plots (50 × 50 m), sown with three different seed mixtures (competitive and two alternatives) and unmanaged or managed by mowing, and on 10 surrounding field margins. 3. The responses of the two pollinator groups to vegetation succession were distinctly different. Bumblebees showed a very strong positive response to the diverse seed mixture with abundant floral resources, and their abundance peaked in the first year. The species richness and abundance of Lepidoptera were increased gradually, suggesting differential colonization speeds of species and a gradual establishment of populations. Lepidopteran abundance reached the level of the field margins in 3 years, whereas the corresponding species richness level was not reached. The benefits of the alternative seed mixtures were less pronounced in Lepidoptera than in bumblebees. No effects of the mowing treatment on either species group were detected. 4. Within both pollinator groups, the response to vegetation succession was associated with species traits. In bumblebees, long-tongued species (indicating specialization) were increased during succession. In butterflies and diurnal moths, colonization success of species was strongly correlated with their wing span (indicating mobility). The most successful colonizers in butterflies were grass feeders and in diurnal moths the species feeding on leguminous plants at the larval stage. 5. Synthesis and applications. The ecological requirements of different pollinator groups should be taken into account when establishing set-aside. Supporting bumblebees is possible even on short-term set-aside, assuming nectar and pollen sources are made available. The occurrence of butterflies and diurnal moths is strongly driven by additional factors, such as the availability of larval host plants as well as adult mobility, which calls for set-aside management regimes to be in place for several years. [ABSTRACT FROM AUTHOR]

The article presents a case study of bumblebee conservation. According to the authors, bumblebees are entirely dependent on flowers for energic and developmental requirements and are also an economically important pollinating insect. An overview of global bumblebee population declines, the increased academic interest in bumblebees, and six key areas regarding bumblebee conservation, including population size, dispersal abilities, and foraging range, is presented.

We have little idea how landscape-scale factors influence the success of wild bumblebee nests over time. Here for the first time we use molecular markers to estimate within-season changes in the numbers of nests. Workers of two bumblebee species were sampled in an arable landscape in late May-June and late July-August, and the numbers of nests represented in each sample were estimated. We compare the methods available to estimate nest number from such samples and conclude that methods which allow for heterogeneity in the probability of capture of nests provide the best fit to our data. Changes in numbers of nests at the two time points were used to infer nest survival. The two bee species appeared to differ markedly in survival over time, with estimates of 45% of nests surviving for Bombus lapidarius and 91% for B. pascuorum. However, our data suggest that the foraging range of B. pascuorum may be greater in late season, which would lead us to overestimate nest survival in this species. Differential survival may also reflect differences in phenology between the two species. The land use class which had the most consistent effects on nest number and survival was gardens; for B. lapidarius, the area of gardens within a 750 and 1000 m radius positively influenced nest survival, while for B. pascuorum, the number of nests in late samples was higher at sites with more gardens within a 500 and 750-m radius. For B. pascuorum, the area of grassland within a 250 and 500-m radius also positively influenced nest number in late samples, probably because this is the preferred nesting habitat for this species. The importance of gardens is in accordance with previous studies which suggest that they now provide a stronghold for bumblebees in an otherwise impoverished agricultural environment; furthermore, our data suggest that the positive influence of gardens on bumblebee populations can spill over at least 1 km into surrounding farmland. Synthesis and applications. The substantial effects that even small areas of local resources such as rough grassland or clover leys can have on bumblebee nest numbers and survival is of clear relevance for the design of pollinator management strategies. [ABSTRACT FROM AUTHOR]

1. A seed-feeding biocontrol agent Bruchidius villosus was released in New Zealand (NZ) to control the invasive European shrub, broom Cytisus scoparius, in 1988 but it was subsequently considered unable to destroy sufficient seed to suppress broom populations. We hypothesized that an invasive mite Varroa destructor, which has caused honeybee decline in NZ, may cause pollinator limitation, so that the additional impact of B. villosus might now reach thresholds for population suppression. 2. We performed manipulative pollination treatments and broad-scale surveys of pollination, seed rain and seed destruction by B. villosus to investigate how pollinator limitation and biocontrol interact throughout the NZ range of broom. 3. The effect of reduced pollination in combination with seed-destruction was explored using a population model parameterized for NZ populations. 4. Broom seed rain ranged from 59 to 21 416 seeds m−2 from 2004 to 2008, and was closely correlated with visitation frequency of honeybees and bumblebees. Infestation of broom seeds by B. villosus is expected to eventually reach 73% (the average rate observed at the localities adjacent to early release sites). 5. The model demonstrated that 73% seed destruction, combined with an absence of honeybee pollination, could cause broom extinction at many sites and, where broom persists, reduce the intensity of treatment required to control broom by conventional means. 6. Nevertheless, seed rain was predicted to be sufficient to maintain broom invasions over many sites in NZ, even in the presence of the varroa mite and B. villosus, largely due to the continued presence of commercial beehives that are treated for varroa mite infestation. 7. Synthesis and applications. Reduced pollination through absence of honeybees can reduce broom seed set to levels at which biocontrol can be more effective. To capitalize on the impact of the varroa mite on feral honeybees, improved management of commercial beehives (for example, withdrawal of licences for beekeepers to locate hives on Department of Conservation land) could be used as part of a successful integrated broom management programme at many sites in NZ. [ABSTRACT FROM AUTHOR]

1. New incentives at the national and international level frequently lead to substantial structural changes in agricultural landscapes. Subsidizing energy crops, for example, recently fostered a strong increase in the area cultivated with oilseed rape Brassica napus across the EU. These changes in landscape structure affect biodiversity and associated ecosystem services. 2. Mass-flowering oilseed rape has been shown to positively affect colony growth and densities of bumblebees, which may enhance pollination services in agroecosystems. Not considered, however, have been species-specific traits of pollinators resulting in disproportionate benefits from these recurrent resource pulses. A subsequent community shift towards the subsidized species potentially distorts plant–pollinator interactions in the surrounding landscape. 3. We analysed the effects of mass-flowering crops on the abundance of legitimate long-tongued bumblebee pollinators, nectar robbing by illegitimate short-tongued bumblebees and seed set in the long-tubed flowers of red clover Trifolium pratense in 12 landscape sectors with differing amounts of oilseed rape. 4. Densities of long-tongued bumblebees visiting long-tubed plants decreased with increasing amounts of oilseed rape. The simultaneous increase of nectar robbing suggests that resource depletion is a likely explanation for this decline which may lead to a distortion in plant–pollinator interactions. The decline in long-tongued bumblebees, however, did not result in an immediate effect on seed set. In contrast, seed set increased with increasing amounts of semi-natural habitats, indicating the positive effects of these habitats on the legitimate long-tongued pollinators. 5. Synthesis and applications. Accounting for species-specific traits is essential in evaluating the ecological impacts of land-use change. The disproportional trait-specific benefits of increasing oilseed rape to short-tongued bumblebees may abet an increasingly pollinator-dependent agriculture but simultaneously threaten the more specialized and rare long-tongued species and their functions. Semi-natural habitats were found to positively affect seed set in long-tubed plants indicating that they can counteract the potentially distorting effects of transient mass-flowering crops on plant–pollinator interactions in agroecosystems. Future agri-environmental schemes should aim to provide diverse and continuous resources matching trait-specific requirements of various pollinators in order to avoid resource competition. Thereby they harmonize the economic interest in abundant pollinators and the conservation interest in protecting rare species. [ABSTRACT FROM AUTHOR]

1. Increased agricultural intensification has led to well-documented declines in the fauna and flora associated with intensive grasslands in the UK. We aimed to quantify the effectiveness of different field margin management strategies for putting bumblebee and butterfly biodiversity back into intensive grasslands. 2. Using four intensive livestock farms in south-west England, we manipulated conventional management practices (addition of inorganic fertilizer, cutting frequency and height, and aftermath grazing) to generate seven grass-based treatments along a gradient of decreasing management intensity. We also tested two more interventionist treatments which introduced sown components into the sward: (i) a cereal, grass and legume mix, and (ii) a diverse conservation mix with kale, mixed cereals, linseed and legumes. These crop mixtures were intended to provide forage and structural resources for pollinators but were not intended to have agronomic value as livestock feed. Using a replicated block design, we monitored bumblebee and butterfly responses in 27 plots (10 × 50 m) in each farm from 2003 to 2006. 3. Bumblebees were most abundant, species-rich and diverse in the sown treatments and virtually absent from the grass-based treatments. The diverse conservation mix treatment supported larger and more diverse bumblebee assemblages than the cereal, grass and legume mix treatment. The sown treatments, and the most extensively managed grass-based treatments, had the highest abundance, species richness and diversity of adult butterflies, whereas butterfly larvae were only found in the grass-based treatments. 4. Bumblebee and butterfly assemblage structure was driven by floral abundance, floral richness, the availability of nectar resources, and sward structure. Only vegetation cover was correlated with butterfly larval abundance. 5. Synthesis and applications. This study has identified management options in the margins of intensive grasslands which can enhance bumblebee and butterfly biodiversity. Extensification of conventional grass management by stopping fertilization, reducing cutting frequency and not grazing, benefits butterflies. However, to enhance bumblebees requires a more interventionist approach in the form of sowing flower-rich habitat. Both approaches are potentially suitable for adoption in agri-environment schemes in the UK and Europe. [ABSTRACT FROM AUTHOR]

1. Pollination is a vital ecosystem service, which is endangered by the ongoing declines of pollinators. These declines also affect bumblebees ( Bombus spp.), which are important generalist pollinators in agricultural landscapes. Most studies focussing on the conservation of bumblebees have investigated the effects of local flower-rich habitats on bumblebee density and diversity. However, bumblebee densities do not necessarily correlate with the colonies’ reproductive success (i.e. the presence or absence of males and/or queens). 2. We analysed the effects of landscape-wide availability of mass flowering oilseed rape Brassica napus on the growth and sexual reproduction of Bombus terrestris colonies. Thirty-two young colonies were established and monitored in different resource environments represented by 16 landscapes (circular study areas with 3000 m radius) with large or small amounts of oilseed rape. As an indicator of colony growth, we used weight gain, which was strongly correlated with the numbers of brood cells in the colonies. 3. The colonies gained significantly more weight in study areas with large amounts of oilseed rape particularly during early colony stages. 4. Despite early weight gain, the colonies in study areas with large amounts of oilseed rape did not reproduce more successfully. The frequencies of colonies that produced males and/or queens did not differ between the two resource environments. 5. Synthesis and applications. Early mass flowering oilseed rape has a beneficial effect on colony growth, which however, does not translate into a greater likelihood of colonies producing sexual offspring. This may be due to food plant scarcity later in the colony cycle. Conservation measures should enhance food plant availability in agricultural landscapes, particularly during the most critical phases of the colony cycle: the colony establishment in spring and the reproductive phase in mid- to late summer. [ABSTRACT FROM AUTHOR]

1. Bumblebees provide an important pollination service to both crops and wild plants. Many species have declined in the UK, particularly in arable regions. While bumblebee forage requirements have been widely studied, there has been less consideration of whether availability of nesting sites is limiting. It is important to know which habitats contain the most bumblebee nests per unit area in order to guide conservation and management options; particularly in the light of current emphasis on environmental stewardship schemes for farmed landscapes. However, it is extremely difficult to map the distribution of bumblebee nests. 2. We describe the findings of the National Bumblebee Nest Survey, a structured survey carried out by 719 volunteers in the UK during early summer 2004. The surveyors used a defined protocol to record the presence or absence of bumblebee nests in prescribed areas of gardens, short grassland, long grassland and woodland, and along woodland edge, hedgerows and fence lines. The records allowed us to estimate the density of bumblebee nests in each of these habitats for the first time. 3. Nest densities were high in gardens (36 nests ha−1), and linear countryside habitats (fence lines, hedgerows, woodland edge: 20–37 nests ha−1), and lower in non-linear countryside habitats (woodland and grassland: 11–15 nests ha−1). 4. Findings on nest location characteristics corroborate those of an earlier survey carried out in the UK ( Fussell & Corbet 1992 ). 5. Synthesis and applications. Gardens provide an important nesting habitat for bumblebees in the UK. In the countryside, the area occupied by linear features is small compared with that of non-linear features. However, as linear features contain high densities of nests, management options affecting such features may have a disproportionately large effect on bumblebee nesting opportunities. Current farm stewardship schemes in the UK are therefore likely to facilitate bumblebee nesting, because they provide clear guidance and support for ‘sympathetic’ hedgerow and field margin management. [ABSTRACT FROM AUTHOR]

1. Declines in abundance and diversity of bumble bees ( Bombus spp.) in Europe have been linked to agricultural intensification and the resulting loss of suitable foraging and nesting habitats. Environmental Stewardship (ES) is a new scheme in England offering the opportunity to restore habitats of value for these important pollinators to agricultural land. Scientific evaluation of the options prescribed within the scheme is essential to ensure that their objectives are met and that the benefits can be realized by the full bumble bee species assemblage. 2. We compared the efficacy of different ES options for field margins on arable land in enhancing the abundance and diversity of flowering resources and foraging bumble bees. Our study was conducted over 3 years using a multisite experiment. 3. Overall, uncropped margins sown with mixtures containing nectar and pollen-producing plants were more effective in providing bumble bee forage than margins sown with a grass mix, allowed to regenerate naturally or managed as conservation headlands. 4. A mixture of agricultural legumes established quickly and attracted on average the highest total abundance and diversity of bumble bees, including the rare long-tongued species Bombus ruderatus and Bombus muscorum. However, marked differences were observed between species and sexes in their responses to field margin management over time. 5. A diverse mixture of native wildflowers attracted more of the shorter-tongued Bombus spp. and provided greater continuity of forage resources, especially early in the season. Allowing Cirsium spp. to flower on such margins also increased their attractiveness to male bumble bees. 6. Synthesis and applications. Our results suggest that the legume-based ‘pollen and nectar flower mix’, as prescribed under Entry Level Stewardship in England, can quickly provide a highly attractive forage resource for bumble bees, but that issues of seasonal flowering phenology and longevity of the mixture need to be addressed. Establishment of ‘floristically enhanced margins’ under Higher Level Stewardship will be important to provide diverse perennial communities of forage plants and to support a greater range of Bombus spp. and other pollinators. The population-level responses of bumble bees to introduced seed mixtures and other agri-environment options require further study in order to maximize the benefits of such schemes in intensively farmed landscapes. [ABSTRACT FROM AUTHOR]

1. Although invasive species are major topics of research, little consideration has been given to the implications of introducing non-native subspecies or beneficial organisms such as pollinators. However, the extensive trade in bumble bees as pollinators of glasshouse crops involves both. Within regions in Europe, the importation of non-native commercially reared subspecies of Bombus terrestris could endanger native bumble bees through competitive displacement and/or hybridization. 2. This study made a direct ecological comparison between commercially imported and native B. terrestris colonies growing in the wild in the UK. In particular, using a paired design, we compared the nectar-foraging performance and reproductive outputs of commercial and native colonies growing under identical field conditions. 3. Commercial colonies performed well in the field, with substantially higher nectar-foraging rates than native colonies in four out of five locations. Nectar-foraging performance was positively correlated with forager size, with commercial bees being consistently larger than native bees. 4. All seven commercial colonies studied produced gynes (new queens), with two colonies each producing in excess of 50. In contrast, only two out of seven native colonies produced gynes, and those only produced small numbers (five in total). Males were produced by all colonies but there were no significant differences in numbers between commercial and native subspecies. 5. Synthesis and applications. The high reproductive success of commercial colonies indicates that there is an appreciable risk that they will become established and spread within the UK. Furthermore, their superior foraging ability and large colony size could lead them to out-compete native bumble bees. Clearly the invasive potential of non-native subspecies and/or beneficial organisms should not be overlooked. With respect to the current importation of commercial bumble bees, we strongly recommend a precautionary approach: native species and subspecies should be locally reared and the use/disposal of bees should be strictly regulated. [ABSTRACT FROM AUTHOR]

1. Little is known about the pollinators of rare plants, which is cause for concern given that pollination is essential for the long-term survival of most plant species. The aim of this study was to determine the probable pollinators of three species of rare arable weed: red hemp-nettle Galeopsis angustifolia, small-flowered catchfly Silene gallica and spreading hedge-parsley Torilis arvensis. Species of arable weed are among those suffering the greatest declines in the UK. 2. Five field sites were chosen, two of which were sampled in 2 years. Visitation and pollen transport webs were constructed for the entire plant–pollinator community at each site. Visitation webs described the frequency with which each insect species visited each plant species. Pollen transport webs quantified which insect species transported the pollen of which plant species. 3. A wide range of insect species visited the three plant species. A pollinator importance index was calculated that combined information on both the relative abundance of each insect carrying the pollen of the rare plant and its pollen fidelity. Using this method Galeopsis angustifolia was most likely to be pollinated by Bombus pascuorum at one site and Sphaerophoria scripta at another. Silene gallica was also likely be pollinated by Sphaerophoria scripta. 4. The pollinator fauna of the three plant species varied considerably across their geographical range, but less from one year to the next. 5. Synthesis and applications. All three species of rare plant were linked to other plant species in the community by shared pollinators. In many cases these other plant species constituted the primary food sources for the shared pollinators. Therefore, the long-term survival of rare plant populations is likely to depend on the more common plant species in the community. We recommend that management of the rare plants studied here should also include the protection and management of populations of some of the more common plant species in their respective communities. [ABSTRACT FROM AUTHOR]

Summary1.To help evaluate the worth of alternative pollinators in agriculture, we present a theoretical framework for comparing the effectiveness of two or more pollinators by measuring pollen removal and deposition. 2.We report pollen removal and deposition data by Apis mellifera and Bombus spp. during single visits to four cultivars of apples (Golden Delicious, Starkrimson Delicious, Empire/MacIntosh and Rome) and Mission almond. 3.Apis and Bombus removed similar amounts of pollen from apple flowers but Bombus deposited more pollen on stigmas. Pollen-collecting bees removed more pollen from apple anthers than nectar-collecting bees. Apis that approached nectaries laterally deposited substantially less pollen than other visitors. 4.Apis and Bombus removed and deposited similar amounts of pollen on almond flowers. Apis tended to remove more during pollen-collecting visits than nectar-collecting visits. The type of resource sought did not significantly influence deposition. 5.Based on removal and deposition data, additions of Bombus may increase pollen delivery in apple orchards but reduce pollen delivery in almond orchards if Apis already serve as primary pollinators. Additional data on inter-tree and inter-row flights would be necessary to know how much these changes in pollen transfer might affect fertilization. 6.Measures of pollen-transfer effectiveness do not provide a complete assessment of pollination value, but can serve as a general, inexpensive tool for pre-screening possible alternative pollinators. [ABSTRACT FROM AUTHOR]