Body-size-dependent effects of landscape-level resource energetics on pollinator abundance in woodland remnants

Land use change alters floral resource availability, thereby contributing to declines in important pollinators. However, the severity of land use impact varies by species, influenced by factors such as dispersal ability and resource specialization, both of which can correlate with body size. Here. we test whether floral resource availability in the surrounding landscape (the 'matrix') influences bee species' abundance in isolated remnant woodlands, and whether this effect varies with body size. We sampled quantitative flower-visitation networks within woodland remnants and quantified floral energy resources (nectar and pollen calories) available to each bee species both within the woodland and the matrix. Bee abundance in woodland increased with floral energy resources in the surrounding matrix, with strongest effects on larger-bodied species. Our findings suggest important but size-dependent effects of declining matrix floral resources on the persistence of bees in remnant woodlands, highlighting the need to incorporate landscape-level floral resources in conservation planning for pollinators in threatened natural habitats.

Effects of study design parameters on estimates of bee abundance and richness in agroecosystems: a meta-analysis

Pollinators are critical for agricultural production and food security, leading to many ongoing surveys of pollinators (especially bees) in crop and adjacent landscapes. These surveys have become increasingly important to better understand the community of potential pollinators, quantify relative insect abundance, and secure crop ecosystem services. However, as some bee populations are declining, there is a need to align and improve bee survey efforts, so that they can best meet research and conservation goals, particularly in light of the logistical and financial constraints of conducting such studies. Here, we mined the existing literature on bee surveys in or around agricultural lands to better understand how sampling methods can be optimized to maximize estimates of 2 key measures of bee communities (abundance and richness). After reviewing 72 papers spanning 20 yr of publication, we found that study duration, number of sites, sampling time, and sampling method most significantly influenced abundance, while the number of trips per year and collection method significantly influenced richness. Our analysis helps to derive thresholds, priorities, and recommendations that can be applied to future studies describing bee communities in agroecosystems.

A quantitative survey of the blueberry (Vaccinium spp.) culturable nectar microbiome: variation between cultivars, locations, and farm management approaches

Microbes in floral nectar can impact both their host plants and floral visitors, yet little is known about the nectar microbiome of most pollinator-dependent crops. In this study, we examined the abundance and composition of the fungi and bacteria inhabiting Vaccinium spp. nectar, as well as nectar volume and sugar concentrations. We compared wild V. myrsinites with two field-grown V. corymbosum cultivars collected from two organic and two conventional farms. Differences in nectar traits and microbiomes were identified between V. corymbosum cultivars but not Vaccinium species. The microbiome of cultivated plants also varied greatly between farms, whereas management regime had only subtle effects, with higher fungal populations detected under organic management. Nectars were hexose-dominant, and high cell densities were correlated with reduced nectar sugar concentrations. Bacteria were more common than fungi in blueberry nectar, although both were frequently detected and co-occurred more often than would be predicted by chance. "Cosmopolitan" blueberry nectar microbes that were isolated in all plants, including Rosenbergiella sp. and Symmetrospora symmetrica, were identified. This study provides the first systematic report of the blueberry nectar microbiome, which may have important implications for pollinator and crop health.

Forests are critically important to global pollinator diversity and enhance pollination in adjacent crops

Although the importance of natural habitats to pollinator diversity is widely recognized, the value of forests to pollinating insects has been largely overlooked in many parts of the world. In this review, we (i) establish the importance of forests to global pollinator diversity, (ii) explore the relationship between forest cover and pollinator diversity in mixed-use landscapes, and (iii) highlight the contributions of forest-associated pollinators to pollination in adjacent crops. The literature shows unambiguously that native forests support a large number of forest-dependent species and are thus critically important to global pollinator diversity. Many pollinator taxa require or benefit greatly from resources that are restricted to forests, such as floral resources provided by forest plants (including wind-pollinated trees), dead wood for nesting, tree resins, and various non-floral sugar sources (e.g. honeydew). Although landscape-scale studies generally support the conclusion that forests enhance pollinator diversity, findings are often complicated by spatial scale, focal taxa, landscape context, temporal context, forest type, disturbance history, and external stressors. While some forest loss can be beneficial to pollinators by enhancing habitat complementarity, too much can result in the near-elimination of forest-associated species. There is strong evidence from studies of multiple crop types that forest cover can substantially increase yields in adjacent habitats, at least within the foraging ranges of the pollinators involved. The literature also suggests that forests may have enhanced importance to pollinators in the future given their role in mitigating the negative effects of pesticides and climate change. Many questions remain about the amount and configuration of forest cover required to promote the diversity of forest-associated pollinators and their services within forests and in neighbouring habitats. However, it is clear from the current body of knowledge that any effort to preserve native woody habitats, including the protection of individual trees, will benefit pollinating insects and help maintain the critical services they provide.

Large Remaining Forest Habitat Patches Help Preserve Wild Bee Diversity in Cultivated Blueberry Bush

Global declines in wild and managed bee populations represent a major concern for the agricultural industry. Such declines result, in part, from the loss of natural and semi-natural habitats in and around agricultural ecosystems. However, remaining forest patches in heavily modified landscapes represent nesting habitats that may be crucial to preserving wild bees and their services. Because wild bees are the main pollinators of fruit crops, preserving potential nesting habitats might be particularly important for the crops’ yield and profitability. Here, we assessed whether the abundance and richness of visiting wild bees in blueberry crops relates to the amount of surrounding forest cover and if so, whether those relationships varied with spatial scale. Specifically, we sampled wild bee communities in 18 blueberry fields during the blooming period in Montérégie, Quebec, Canada, where sampling consisted of pan trap triplets and direct observation of flower visitors on blueberry bushes. Then, we quantified the proportion of forest in radii of 0.5 km, 1 km, and 2 km around each field. Wild bee abundance was positively related to the proportion of forest habitat surrounding the crop field, but the relationship for wild bee richness was less clear. Moreover, these relationships were strongest at 1 and 2 km radii of measured land cover. Overall, pollinator diversity was highest when at least 30% of the surrounding landscape consisted of forest patches, representing a total area of at least 1 km2. Our results suggest that preserving large habitat patches in agricultural landscapes can help prevent further decline in wild bee diversity while maximizing pollination services to fruit crops.

Diverse flower-visiting responses among pollinators to multiple weather variables in buckwheat pollination

Response diversity to environmental change among species is important for the maintenance of ecosystem services, but response diversity to changes in multiple environmental parameters is largely unexplored. Here, we examined how insect visitations to buckwheat flowers differ among species groups in response to changes in multiple weather variables and landscape structures. We found differences in responses to changes in weather conditions among insect taxonomic groups visiting buckwheat flowers. Beetles, butterflies, and wasps were more active in sunny and/or high-temperature conditions, whereas ants and non-syrphid flies showed the opposite pattern. When looking closely, the different response pattern among insect groups was itself shown to be different from one weather variable to another. For instance, large insects were responsive to temperatures more than small insects while smaller insects were responsive to sunshine duration more than large insects. Furthermore, responses to weather conditions differed between large and small insects, which agreed with the expectation that optimal temperature for insect activity depends on body size. Responses to spatial variables also differed; large insects were more abundant in fields with surrounding forests and mosaic habitats, whereas small insects were not. We suggest that response diversity at multiple spatial and temporal niche dimensions should be a focus of future studies of the biodiversity-ecosystem service relationships.

Decline in wild bee species richness associated with honey bee (Apis mellifera L.) abundance in an urban ecosystem

The spatial heterogeneity of urban landscapes, relatively low agrochemical use, and species-rich floral communities often support a surprising diversity of wild pollinators in cities. However, the management of Western honey bees (Apis mellifera L.) in urban areas may represent a new threat to wild bee communities. Urban beekeeping is commonly perceived as an environmentally friendly practice or a way to combat pollinator declines, when high-density beekeeping operations may actually have a negative influence on native and wild bee populations through floral resource competition and pathogen transmission. On the Island of Montréal, Canada there has been a particularly large increase in beekeeping across the city. Over the years following a large bee diversity survey ending in 2013, there was an influx of almost three thousand honey bee colonies to the city. In this study, we examined the wild bee communities and floral resources across a gradient of honey bee abundances in urban greenspaces in 2020, and compared the bee communities at the same sites before and after the large influx of honey bees. Overall, we found a negative relationship between urban beekeeping, pollen availability, and wild bee species richness. We also found that honey bee abundance had the strongest negative effect on small (inter-tegular span <2.25 mm) wild bee species richness. Small bee species may be at higher risk in areas with abundant honey bee populations as their limited foraging range may reduce their access to floral resources in times of increased competition. Further research on the influence of urban beekeeping on native and wild pollinators, coupled with evidence-based beekeeping regulations, is essential to ensure cities contain sufficient resources to support wild bee diversity alongside managed honey bees.

Landscape or local? Distinct responses of flower visitor diversity and interaction networks to different land use scales in agricultural tropical highlands

Land use change has been identified as a cause for biodiversity loss and has significant effects on pollinators and their interactions with plants. Interaction network analyses complement diversity estimators by providing information on the stability and functionality of the plant-pollinator community in an ecosystem. However, how land use changes affect insect diversity, and the structure of their plant-insect interaction networks, could depend on the intensity of the disturbance but also may be a matter of scale. Our study was carried out in a tropical highland landscape dominated by intense, yet diverse, small-scale agriculture. We studied the effects of land use, at a landscape scale, and local cover and plant ecological descriptors, at a local scale; on diversity descriptors of insect pollinator communities, the abundance of the most frequent flower visitors, and their interaction networks. Seminatural vegetation favored insect flower visitors at both scales. At the landscape scale, human settlements positively influenced bee diversity, and seminatural areas favored the abundance of frequent hoverfly and bumblebee species. At the local scale, bare soil cover negatively influenced honeybee abundance while flower-rich covers positively related to bumblebee abundance. Only local scale variables had influence on network metrics. Bare soil cover was related to higher network specialization, probably due to a low rate of honeybee interactions. Flower-rich covers negatively influenced network connectance but favored modularity. These results suggest that flower resources, provided by weed areas and flowering crops, promote a high rate of interactions between trophic levels and a non-random structure in the interaction networks that may be helping to sustain network stability. Our results highlight the role of seminatural vegetation, at both scales, in maintaining stable insect pollinator communities and interactions in heterogeneous agricultural landscapes of the tropics.

Anthropogenic effects on the body size of two neotropical orchid bees

To accommodate an ever-increasing human population, agriculture is rapidly intensifying at the expense of natural habitat, with negative and widely reported effects on biodiversity in general and on wild bee abundance and diversity in particular. Cities are similarly increasing in area, though the impact of urbanisation on wild bees is more equivocal and potentially positive in northern temperate regions. Yet agriculture and urbanisation both lead to the loss and alteration of natural habitat, its fragmentation, a potential reduction in floral availability, and warmer temperatures, factors thought to be drivers of wild bee decline. They have also been shown to be factors to which wild bee populations respond through morphological change. Body size is one such trait that, because of its relation to individual fitness, has received growing attention as a morphological feature that responds to human induced modification in land use. Here, we investigated the change in body size of two sympatric orchid bee species on the Yucatan Peninsula of Mexico in response to urbanization and agricultural intensification. By measuring 540 male individuals sampled from overall 24 sites, we found that Euglossa dilemma and Euglossa viridissima were on average smaller in urban and agricultural habitats than in natural ones. We discuss the potential role of reduced availability of resources in driving the observed body size shifts. Agricultural and urban land management in tropical regions might benefit wild bees if it encompassed the planting of flowering herbs and trees to enhance their conservation.

Toward evidence-based decision support systems to optimize pollination and yields in highbush blueberry

Highbush blueberry (Vaccinium spp.) is a globally important fruit crop that depends on insect-mediated pollination to produce quality fruit and commercially viable yields. Pollination success in blueberry is complex and impacted by multiple interacting factors including flower density, bee diversity and abundance, and weather conditions. Other factors, including floral traits, bee traits, and economics also contribute to pollination success at the farm level but are less well understood. As blueberry production continues to expand globally, decision-aid technologies are needed to optimize and enhance the sustainability of pollination strategies. The objective of this review is to highlight our current knowledge about blueberry pollination, where current research efforts are focused, and where future research should be directed to successfully implement a comprehensive blueberry pollination decision-making framework for modern production systems. Important knowledge gaps remain, including how to integrate wild and managed pollinators to optimize pollination, and how to provide predictable and stable crop pollination across variable environmental conditions. In addition, continued advances in pesticide stewardship are required to optimize pollinator health and crop outcomes. Integration of on- and off-farm data, statistical models, and software tools could distill complex scientific information into decision-aid systems that support sustainable, evidence-based pollination decisions at the farm level. Utility of these tools will require multi-disciplinary research and strategic deployment through effective extension and information-sharing networks of growers, beekeepers, and extension/crop advisors.

Different visitation frequencies of native and non-native bees to vines: how much vegetation is necessary to improve fruit production?

Pollination is provided by biodiversity and maintains global food production. We investigated the effects of vegetation cover on the abundance of floral visitor and vine (Vitis labrusca Raf.) production. We expected an increase in both floral visitor frequencies and vineyard yields with an increase in native vegetation cover in the landscape. We also investigated different scenarios of visitor abundance with and without honeybees (Apis mellifera L.). We surveyed floral visitors from ten vineyard plots with different native cover surrounding them and related both visitors and native vegetation to fruit set. Considering some of these vineyards, we compared physical and chemical traits of berries to understand how they vary according to native vegetation. Floral visitor abundance was positively related to native vegetation cover. However, considering only native bee abundance, we found a dual (hyperbolic) response. Apis mellifera (L.) Africanized was the most abundant species and had the highest number of interactions; however, when removed from the network analysis, the relationship between vineyards and native bees became more specialized. The fruit size and mass of berries differed among vineyards, as did some chemical traits related to commercial quality of fruits, such as soluble solids, pH and flavonoids. Vineyards surrounded by intermediate areas of native vegetation present a balance between resource availability from vineyards and native vegetation. Apis and non-Apis (such as flies and small bees) floral visitors, known to have different effects on vine pollination, could hypothetically provide variation in vine production and quality. Considering a near 20% native vegetation increment, there was an enhancement, on average, of ten-fold more berries per bunch, the changing physical and chemical fruit traits by vegetation increment could also increase the aggregate value of vines and the value of pollination services in the economy.

Pollinator decline: what do we know about the drivers of solitary bee declines?

Pollinators and the environments where they live are experiencing increasing human impacts leading to changes, primarily declines, in species richness and population abundances. The drivers of pollinator decline vary. Almost every type human resource use leads to some level of loss of habitat. The effects of pollution, particularly heavy metals, pesticides and the role of disease are increasingly recognized as important drivers of pollinator declines, however, significant gaps in our knowledge exist. Of particular concern is the feedback loop between decreasing pollination service, plant inbreeding, declines in nectar quality and further pollinator decline. When viewed in the context of the abiotic and biotic shifts associated with climate change, we suggest that focusing on ensuring there is adequate habitat remaining to provide resilience should be a central strategy for preserving pollinators.

Complementary Contribution of Wild Bumblebees and Managed Honeybee to the Pollination Niche of an Introduced Blueberry Crop

The entomophilous pollination niche (abundance, phenotypic traits, foraging behaviours and environmental tolerances of insect pollinators) helps to understand and better manage crop pollination. We apply this niche approach to assess how an entomophilous crop (blueberry, Vaccinium ashei) can be expanded into new territories (i.e., northern Spain) far from their original area of domestication (North America). Insect visits to blueberry flowers were monitored in a plantation on 12 different days, at 8 different times during day and covering various weather conditions. Abundance, visitation rate, pollen gathering behaviour, and frequency of inter-plant and inter-row movements were recorded. The pollinator assemblage was basically composed of one managed honeybee species (50.8% of visits) and three native bumblebee species (48.3%). There was a marked pattern of seasonal segregation throughout bloom, with bumblebees dominating the early bloom and honeybee the late bloom. Pollinators also segregated along gradients of daily temperature and relative humidity. Finally, the two pollinator types differed in foraging behaviour, with bumblebees having a visitation rate double that of honeybee, collecting pollen more frequently and changing plant and row more frequently. The spatio-temporal and functional complementarity between honeybee and bumblebees suggested here encourages the consideration of an integrated crop pollination strategy for blueberries, based on the concurrence of both wild and managed bees.

Pollinator interaction flexibility across scales affects patch colonization and occupancy

Global change alters ecological communities and may disrupt ecological interactions and the provision of ecosystem functions. As ecological communities respond to global change, species may either go locally extinct or form novel interactions. To date, few studies have assessed how flexible species are in their interaction patterns, mainly due to the scarcity of data spanning long time series. Using a ten-year species-level dataset on the assembly of mutualistic networks from the Central Valley in California, we test whether interaction flexibility affects pollinators' colonization and persistence and their resulting habitat occupancy in a highly modified landscape. We propose three metrics of interaction flexibility associated with different scales of organization within ecological communities and explore which species' traits affect them. Our results provide empirical evidence linking species' ability to colonize habitat patches across a landscape to the role they play in networks. Phenological breadth and body size had contrasting effects on interaction flexibility. We demonstrate the relationship between mutualistic networks and species' ability to colonize and persist in the landscape, suggesting interaction flexibility as a potential mechanism for communities to maintain ecosystem function despite changes in community composition.

Wild bees as winners and losers: Relative impacts of landscape composition, quality, and climate

Wild bees, like many other taxa, are threatened by land-use and climate change, which, in turn, jeopardizes pollination of crops and wild plants. Understanding how land-use and climate factors interact is critical to predicting and managing pollinator populations and ensuring adequate pollination services, but most studies have evaluated either land-use or climate effects, not both. Furthermore, bee species are incredibly variable, spanning an array of behavioral, physiological, and life-history traits that can increase or decrease resilience to land-use or climate change. Thus, there are likely bee species that benefit, while others suffer, from changing climate and land use, but few studies have documented taxon-specific trends. To address these critical knowledge gaps, we analyzed a long-term dataset of wild bee occurrences from Maryland, Delaware, and Washington DC, USA, examining how different bee genera and functional groups respond to landscape composition, quality, and climate factors. Despite a large body of literature documenting land-use effects on wild bees, in this study, climate factors emerged as the main drivers of wild-bee abundance and richness. For wild-bee communities in spring and summer/fall, temperature and precipitation were more important predictors than landscape composition, landscape quality, or topography. However, relationships varied substantially between wild-bee genera and functional groups. In the Northeast USA, past trends and future predictions show a changing climate with warmer winters, more intense precipitation in winter and spring, and longer growing seasons with higher maximum temperatures. In almost all of our analyses, these conditions were associated with lower abundance of wild bees. Wild-bee richness results were more mixed, including neutral and positive relationships with predicted temperature and precipitation patterns. Thus, in this region and undoubtedly more broadly, changing climate poses a significant threat to wild-bee communities.

Wild bees as winners and losers: Relative impacts of landscape composition, quality, and climate

Wild bees, like many other taxa, are threatened by land-use and climate change, which, in turn, jeopardizes pollination of crops and wild plants. Understanding how land-use and climate factors interact is critical to predicting and managing pollinator populations and ensuring adequate pollination services, but most studies have evaluated either land-use or climate effects, not both. Furthermore, bee species are incredibly variable, spanning an array of behavioral, physiological, and life-history traits that can increase or decrease resilience to land-use or climate change. Thus, there are likely bee species that benefit, while others suffer, from changing climate and land use, but few studies have documented taxon-specific trends. To address these critical knowledge gaps, we analyzed a long-term dataset of wild bee occurrences from Maryland, Delaware, and Washington DC, USA, examining how different bee genera and functional groups respond to landscape composition, quality, and climate factors. Despite a large body of literature documenting land-use effects on wild bees, in this study, climate factors emerged as the main drivers of wild-bee abundance and richness. For wild-bee communities in spring and summer/fall, temperature and precipitation were more important predictors than landscape composition, landscape quality, or topography. However, relationships varied substantially between wild-bee genera and functional groups. In the Northeast USA, past trends and future predictions show a changing climate with warmer winters, more intense precipitation in winter and spring, and longer growing seasons with higher maximum temperatures. In almost all of our analyses, these conditions were associated with lower abundance of wild bees. Wild-bee richness results were more mixed, including neutral and positive relationships with predicted temperature and precipitation patterns. Thus, in this region and undoubtedly more broadly, changing climate poses a significant threat to wild-bee communities.

Diverging landscape impacts on macronutrient status despite overlapping diets in managed (Apis mellifera) and native (Melissodes desponsa) bees

Declining pollinator populations worldwide are attributed to multiple stressors, including the loss of quality forage. Habitat management in agricultural areas often targets honey bees (Apis mellifera L.) specifically, with the assumption that native bees will benefit from an 'umbrella species' strategy. We tested this theory using a conservation physiology approach to compare the effects of landscape composition and floral dietary composition on the physiological status of honey bees and Melissodes desponsa in eastern South Dakota, USA. The total glycogen, lipid and protein concentrations were quantified from field collected bees. Next-generation sequencing of the trnL chloroplast gene from bee guts was used to evaluate dietary composition. The effects of landscape and dietary composition on macronutrient concentrations were compared between bee species. As the mean land-use patch area increased, honey bee glycogen levels increased, though M. desponsa experienced a decrease in glycogen. Protein levels decreased in honey bees as the largest patch index, a measure of single patch dominance, increased versus M. desponsa. Lipids in both species were unaffected by the measured landscape variables. Dietary analysis revealed that honey bees foraged preferentially on weedy non-native plant species, while M. desponsa sought out native and rarer species, in addition to utilizing non-native plants. Both species foraged on Asteraceae, Oleaceae and Fabaceae, specifically Melilotus sp. and Medicago sp. Dietary composition was not predictive of the macronutrients measured for either species. Together, these data highlight the management importance of including patch area in conservation recommendations, as bee species may have divergent physiological responses to landscape characteristics. While solitary bees may forage on weedy introduced plants in agricultural areas, robust strategies should also reincorporate native plant species, though they may not be preferred by honey bees, to maximize overall health and diversity of pollinator communities.

Bee communities and pollination services in adjacent crop fields following flower removal in an invasive forest shrub

The habitat boundaries between crops and seminatural areas influence bee movements and pollination services to crops. Edges also provide favorable conditions for invasive plants, which may usurp pollinators and reduce visitation to native or crop plants. Alternatively, floral displays of alien plants may facilitate, or increase, the pollination success of adjacent plants by attracting more pollinators to the area. Therefore, pollination services of bees from seminatural habitats to crop areas should vary with the presence of invasive floral resources and distance from habitat edges. To test the hypothesis that floral resources of invasive forest shrubs affect the bee community and pollination services in adjacent crop fields, we conducted a 2-yr field experiment along forest-crop edges at five isolated forest remnants. We removed flower buds from a dominant invasive shrub, Lonicera maackii (Amur honeysuckle), along forest-crop edges and paired removals with controls of intact flowers. The bee community, their pollination services, and flower visitation rates were quantified along a 200-m gradient into an adjacent crop field using pan traps and sentinel cucumber plants. Impacts to the bee community were dependent of bee functional traits. Larger bees visited fewer sentinel cucumber flowers in flower removal plots, which corresponded with decreased cucumber pollination compared to plots with honeysuckle flowers at distances >100 m from forest edges. Small-bodied and weaker flying bees visited sentinel plants more frequently closer to the forest edge and increased pollination services to cucumber at distances <100 m from L. maackii shrubs in flower removal plots. After 2 yr, bee abundance and species richness increased within flower removal plots across all distances. High functional diversity of the bee community increased pollination services to sentinel plants and increased cucumber production within 200 m from forest remnants. Our findings suggest that dense floral resources of invasive shrubs suppressed forest-edge bee communities and their pollination services, but also attracted large-bodied generalist bees, which were effective pollinators. This study helps explain how life histories and functional attributes of bees can predict either facilitation or suppression of pollination services to crop or native plants in response to invasive floral resources.

Noncrop Habitat Use by Wild Bees (Hymenoptera: Apoidea) in a Mixed-Use Agricultural Landscape

Homogeneous, agriculturally intense landscapes have abundant records of pollinator community research, though similar studies in the forest-dominated, heterogeneous mixed-use landscape that dominates the northeastern United States are sparse. Trends of landscape effects on wild bees are consistent across homogeneous agricultural landscapes, whereas reported studies in the northeastern United States have not found this consistency. Additionally, the role of noncrop habitat in mixed-use landscapes is understudied. We assessed wild bee communities in the mixed-use lowbush blueberry (Vaccinium angustifolium Ait.) production landscape of Maine, United States at 56 sites in eight land cover types across two regional landscapes and analyzed effects of floral resources, landscape pattern, and spatial scale on bee abundance and species richness. Within survey sites, cover types with abundant floral resources, including lowbush blueberry fields and urban areas, promoted wild bee abundance and diversity. Cover types with few floral resources such as coniferous and deciduous/mixed forest reduced bee abundance and species richness. In the surrounding landscape, lowbush blueberry promoted bee abundance and diversity, while emergent wetland and forested land cover strongly decreased these measures. Our analysis of landscape configuration revealed that patch mixing can promote wild bee abundance and diversity; however, this was influenced by strong variation across our study landscape. More surveys at intra-regional scales may lead to better understanding of the influence of mixed-use landscapes on bee communities.

A dataset of multi-functional ecological traits of Brazilian bees

Worldwide, bees are the most important group of animal pollinators. The ecosystem service they provide is vital in natural areas and croplands, and the taxonomic and functional diversity associated with bees is vital in understanding ecosystem functioning ensuring biodiversity conservation, food security and human livelihoods. A dataset of bees from mountainous areas of Carajás National Forest (eastern Amazon) and Nova Lima (Atlantic Forest) is presented here. It is a compilation of sampling efforts from 1983 to 2018 through the accession of data stored in museum collections. In total, 222 and 144 bee species were recorded in Carajás and Nova Lima, respectively. This represents the most robust dataset of Brazilian bees including species traits (body size, flight range, distribution, crop pollination, sociality and nesting) of 328 species. This dataset contributes to advances in the knowledge of the functional trait ecology of wild bees and can benefit further studies that analyze the response of wild bees to land use and climate changes, and its effects on the provision of crop pollination services.

Exposure of Foraging Bees (Hymenoptera) to Neonicotinoids in the U.S. Southern High Plains

Exposure to pesticides is a major threat to insect pollinators, potentially leading to negative effects that could compromise pollination services and biodiversity. The objectives of this study were to quantify neonicotinoid concentrations among different bee genera and to examine differences attributable to body size and surrounding land use. During the period of cotton planting (May-June), 282 wild bees were collected from habitat patches associated with cropland, grassland, and urban land cover and analyzed for three neonicotinoids (thiamethoxam, clothianidin, and imidacloprid). Twenty bees among eight genera contained one or more of the neonicotinoid compounds and detections occurred in all landscape types, yet with the most detections occurring in cropland-associated habitats. Apis Linnaeus (Hymenoptera: Apidae), Melissodes Latreille (Apidae), Perdita Smith (Andrenidae), and Lasioglossum Curtis (Halictidae) had multiple individuals with neonicotinoid detections. Two of the largest bees (Apis and Melissodes) had the greatest number of detections within genera, yet the relatively small-bodied genus Perdita had the three highest neonicotinoid concentrations reported. The number of detections within a genus and average generic body mass showed a marginally significant trend towards larger bees having a greater frequency of neonicotinoid detections. Overall, the relatively low percentage of detections across taxa suggests practices aimed at conserving grassland remnants in intensified agricultural regions could assist in mitigating exposure of wild bees to agrochemicals, while differences in bee traits and resource use could in part drive exposure. Further work is needed to address variable agrochemical exposures among pollinators, to support strategies for conservation and habitat restoration in affected landscapes.

Pollinator effectiveness in a composite: a specialist bee pollinates more florets but does not move pollen farther than other visitors

PREMISE

Variation in pollinator effectiveness may contribute to pollen limitation in fragmented plant populations. In plants with multiovulate ovaries, the number of conspecific pollen grains per stigma often predicts seed set and is used to quantify pollinator effectiveness. In the Asteraceae, however, florets are uniovulate, which suggests that the total amount of pollen deposited per floret may not measure pollinator effectiveness. We examined two aspects of pollinator effectiveness-effective pollen deposition and effective pollen movement-for insects visiting Echinacea angustifolia, a composite that is pollen limited in small, isolated populations.

METHODS

We filmed insect visits to Echinacea in two prairie restorations and used these videos to quantify behavior that might predict effectiveness. To quantify effective pollen deposition, we used the number of styles shriveled per visit. To quantify effective pollen movement, we conducted paternity analysis on a subset of offspring and measured the pollen movement distance between mates.

RESULTS

Effective pollen deposition varied among taxa. Andrena helianthiformis, a Heliantheae oligolege, was the most effective taxon, shriveling more than twice the proportion of styles as all other visitors. Differences in visitor behavior on a flowering head did not explain variation in effective pollen deposition, nor did flowering phenology. On average, visitors moved pollen 16 m between plants, and this distance did not vary among taxa.

CONCLUSIONS

Andrena helianthiformis is an important pollinator of Echinacea. Variation in reproductive fitness of Echinacea in fragmented habitat may result, in part, from the abundance of this species.

Wildlife Refuges Support High Bee Diversity on the Southern Great Plains

The native prairie of the southern Great Plains has been especially modified by two related forces: conversion of native prairie to agricultural forms of land use and removal of black-tailed prairie dogs (Rodentia: Sciuridae, Cynomys ludovicianus (Ord, 1815)) that act as ecosystem engineers via their burrowing and grazing activities. It is unknown how these changes have affected the native bee community. We surveyed the bee communities in relatively intact native prairie at two National Wildlife Refuges in Texas, quantifying bee community structure as a function of the presence/absence of grazing by prairie dogs. Over a 5-mo sampling period in spring-summer 2013, we found high overall bee diversity (180 species, mostly solitary ground-nesters), with differences detected in diversity between Muleshoe and Buffalo Lake National Wildlife Refuges as well as on and off prairie dog colonies. Although the same three species dominated the bee community at both refuges, most species were represented by relatively few individuals, leading to overall differences in diversity (richness, evenness, and effective number of species) by refuge. Bee diversity differed between sites on and off prairie dog colonies, but in trends that differed by refuge and by index, suggesting that location was more important than prairie dog presence. These results represent a reference fauna against which other regional bee communities in other land-cover types can be compared, but the high spatial heterogeneity we found indicates that detecting effects of landscape change on native bees will be challenging.

Dryland Organic Farming Partially Offsets Negative Effects of Highly Simplified Agricultural Landscapes on Forbs, Bees, and Bee-Flower Networks

Industrialized farming practices result in simplified agricultural landscapes, reduced biodiversity, and degraded species-interaction networks. Thus far, most research assessing the combined effects of farming systems and landscape complexity on beneficial insects has been conducted in relatively diversified and mesic systems and may not represent the large-scale, monoculture-based dryland agriculture that dominates many regions worldwide. Specifically, the effects of farming systems on forbs, bees, and their interactions are poorly understood in highly simplified dryland landscapes such as those in the Northern Great Plains, United States, an area globally important for conventional and organic small grain, pulse, forage, and oilseed production. During a 3-yr (2013-2015) study, we assessed 1) the effects of dryland no-till conventional and tilled organic farming on forbs, bees, and bee-flower networks and 2) the relationship between natural habitat and bee abundance. Flower density and richness were greater in tilled organic fields than in no-till conventional fields, and forb community composition differed between farming systems. We observed high bee diversity (109 taxa) in this highly simplified landscape, and bee abundance, richness, and community composition were similar between systems. Compared with tilled organic fields, bee-flower interactions in no-till conventional fields were poorly connected, suggesting these systems maintain relatively impoverished plant-pollinator networks. Natural habitat (11% of the landscape) did not affect small-bodied bee abundance in either farming system but positively affected large-bodied bees within 2,000 m of crop-field centers. In highly simplified agricultural landscapes, dryland organic farming and no-till conventional farming together support relatively high bee diversity, presumably because dryland organic farming enhances floral resources and bee-flower networks, and no-till management in conventional farming provides undisturbed ground-nesting habitats for wild bees (Hymenoptera: Apoidea).

Effect of Corolla Slitting and Nectar Robbery by the Eastern Carpenter Bee (Hymenoptera: Apidae) on Fruit Quality of Vaccinium corymbosum L. (Ericales: Ericaceae)

Eastern carpenter bees, Xylocopa virginica (L.) (Hymenoptera: Apidae), are among the most abundant native bee visitors to highbush blueberry, Vaccinium corymbosum L., flowers in the northeastern United States, and they sometimes display corolla-slitting behavior to rob nectar. We studied foraging behavior of X. virginica on 14 blueberry cultivars in an experimental planting in Rhode Island, and assessed factors related to slitting frequency, and the effects of slitting on fruit set and blueberry quality. Among 14 cultivars in bloom, an average of 35% (range 16-67%) of flowers were slit in 2017, and 39% (range 20-62%) in 2018. Factors that affected the proportion of corollas slit included cultivar, anther length, flower volume, and number of days in bloom at or above 15°C. Corolla slitting did not affect fruit set. Average weight and percent soluble solids of fruit resulting from slit and non-slit corollas did not differ significantly in two early- ('Bluehaven', 'Earliblue'), two mid- ('Collins', 'Bluecrop'), and two late-season ('Herbert', 'Lateblue') ripening cultivars in 2017. In 2018, average fruit weight and percent soluble solids resulting from slit and non-slit flowers did not differ significantly in most cultivars, but slit corollas resulted in berries with greater mass in two cultivars, 'Bluehaven' and 'Collins'. 'Collins' fruit from non-slit corollas had a significantly higher percentage of soluble solids at maturity than fruit from slit corollas in 2018. Corolla slitting and nectar robbery by X. virginica did not have a significant negative effect on fruit quality under the described growing conditions and pollinator community.

A trait-based approach to predict population genetic structure in bees

Understanding population genetic structure is key to developing predictions about species susceptibility to environmental change, such as habitat fragmentation and climate change. It has been theorized that life-history traits may constrain some species in their dispersal and lead to greater signatures of population genetic structure. In this study, we use a quantitative comparative approach to assess if patterns of population genetic structure in bees are driven by three key species-level life-history traits: body size, sociality, and diet breadth. Specifically, we reviewed the current literature on bee population genetic structure, as measured by the differentiation indices Nei's G_ST, Hedrick's G'_ST , and Jost's D. We then used phylogenetic generalised linear models to estimate the correlation between the evolution of these traits and patterns of genetic differentiation. Our analyses revealed a negative and significant effect of body size on genetic structure, regardless of differentiation index utilized. For Hedrick's G'_ST and Jost's D, we also found a significant impact of sociality, where social species exhibited lower levels of differentiation than solitary species. We did not find an effect of diet specialization on population genetic structure. Overall, our results suggest that physical dispersal or other functions related to body size are among the most critical for mediating population structure for bees. We further highlight the importance of standardizing population genetic measures to more easily compare studies and to identify the most susceptible species to landscape and climatic changes.

Pollination Services from Insects in Homegardens in the Chengdu Plain will be Confronted with Crises

Chengdu Plain is one of China’s most important agricultural production zones and has a large human population. Agricultural crops require insect pollination to increase yield and quality, which is especially important in plains areas where forest area is small. Homegardens are the main habitat of pollinators. The present study identified the importance of insect pollination in homegardens in the Chengdu Plain through field investigations and comparative experiments and revealed the risk to pollination services caused by the decrease in diversity and population of managed and wild pollinators. The results showed that (1) prohibiting all insect pollination (treatment A) and prohibiting managed bee pollination (treatment B) significantly reduced the yield and seed number of rapeseed and significantly reduced the size, weight, and sweetness of peach fruit, but had no significant effects on plums; (2) the dependence on insect pollination and the economic values of insect pollination for rapeseed and peaches are 0.56 and $85.1 million and 0.44 and $31.0 million, respectively; (3) there were 23 flower-visiting pollinator species at the experimental sites including: four species of managed bees and 19 species of wild pollinators. The peak time for pollinators to visit flowers was 11:00 to 15:00, and the managed bees accounted for over 67.55% of these visits; (4) within a radius of 1000 m from the site, 58.06% of the bees were non-locally managed, and the bee population managed locally by farmers decreased; and (5) compared with 2008, the number of homegardens decreased by 17.24%, the managed bees within the homegardens decreased by 62.05%, and the disappearance and destruction of homegardens led to a significant reduction in wild pollinators.

Meta-analysis reveals that pollinator functional diversity and abundance enhance crop pollination and yield

How insects promote crop pollination remains poorly understood in terms of the contribution of functional trait differences between species. We used meta-analyses to test for correlations between community abundance, species richness and functional trait metrics with oilseed rape yield, a globally important crop. While overall abundance is consistently important in predicting yield, functional divergence between species traits also showed a positive correlation. This result supports the complementarity hypothesis that pollination function is maintained by non-overlapping trait distributions. In artificially constructed communities (mesocosms), species richness is positively correlated with yield, although this effect is not seen under field conditions. As traits of the dominant species do not predict yield above that attributed to the effect of abundance alone, we find no evidence in support of the mass ratio hypothesis. Management practices increasing not just pollinator abundance, but also functional divergence, could benefit oilseed rape agriculture.

Multi-scalar drivers of biodiversity: local management mediates wild bee community response to regional urbanization

It is critical to understand the specific drivers of biodiversity across multiple spatial scales, especially within rapidly urbanizing areas, given the distinct management recommendations that may result at each scale. However, drivers of biodiversity patterns and interactions between drivers are often only measured and modeled at a single scale. In this study, we assessed bee community composition at three time periods in 20 grassland and 20 agriculture sites located across two major metroplexes. We examined how local environmental variables and surrounding landscape composition impact bee abundance, richness, and evenness, including comparisons between groups with different nesting strategies and body sizes. We collected nearly 13,000 specimens and identified 172 species. We found that levels of regional land use differentially impacted bee abundance and diversity depending on local habitat management. Specifically, within agriculture sites, bee richness was greater with increasing landscape-level seminatural habitat, while in grassland sites, bee richness was similar across landscapes regardless of seminatural habitat cover. Bee evenness at both site types declined with increasing landscape-level habitat heterogeneity, due to an increase of rare species at the grassland sites, but not in the agricultural sites, further indicating that diversity is driven by the interaction of local habitat quality and landscape-level habitat composition. We additionally found that agriculture sites supported higher abundances, but not richness, of small-bodied and below-ground nesting bees, while grassland sites supported higher abundances of aboveground nesting bees, and higher richness of large-bodied species. Increased levels of local bare ground were significantly related to multiple metrics of bee diversity, including greater belowground nesting bee abundance and richness. Local floral richness was also significantly related to increases of overall bee abundance, as well as the abundance and richness of small bees. Overall, we suggest that local land managers can support bee abundance and diversity by conserving areas of bare soil and promoting native floral diversity, the latter especially critical in highly urban agricultural spaces. Our results provide the first documentation of significant interactions between local habitat management and landscape composition impacting insect communities in urban systems, indicating that bee conservation practices depend critically on land use interactions across multiple spatial scales.

Landscape and local site variables differentially influence pollinators and pollination services in urban agricultural sites

Urbanization has detrimental effects on biodiversity and ecosystem functioning, as agricultural and semi-natural habitats are converted into landscapes dominated by built features. Urban agricultural sites are a growing component of urban landscapes and have potential to serve as a source of biodiversity conservation and ecosystem service provisioning in urban areas. In 19 urban agricultural sites, we investigated how surrounding land cover and local site variables supported bees and pollination services. We found the abundance of bees differentially responded to landscape and local scale variables depending on body size and nesting habit. Large-bodied bees, Bombus and Apis species, were positively associated with increasing amounts of impervious cover, while the abundance of small-bodied soil nesting Halictus species increased as the proportion of flower area, a local variable, increased. Bee richness declined with increasing levels of impervious cover, while bee community composition changed along a gradient of increasing impervious cover. Pollination services, measured at each site using sentinel cucumber plants, declined as hardscape, a local variable, increased. To improve bee conservation and pollination services in urban agricultural sites, our results suggest urban planning strategies should minimize impervious cover at large spatial scales while land managers should focus locally on incorporating floral resources, which increases food and nesting resources especially for smaller bee species. Local site design coupled with regional urban planning can advance the success of urban agriculture, while benefiting biodiversity by creating opportunities for pollinator conservation in urban landscapes.

Pollination of Granadilla (Passiflora ligularis) Benefits From Large Wild Insects

The contribution of wild pollinators to food production has recently been assessed for many crops, although it remains unclear for several tropical crops. Granadilla (Passiflora ligularis Juss), a crop native to the tropical Andes, is one such crop where a gap exists regarding comprehensive knowledge about its pollination system. In a field experiment in the Colombian Andes, we 1) describe flower visitors in terms of visit quantity (visitation rate) and quality (touches of flower-reproductive structures), 2) assess the pollination system by comparing fruit set and fruit weight per flower in three pollination treatments: pollinator exclusion, open pollination, and supplementary pollination, and 3) evaluate pollination deficits (difference between open and supplementary pollination) in relation to pollinator density. We observed 12 bee species visiting granadilla flowers, with Apis mellifera Linnaeus being the most frequent species. However, large bees such as Xylocopa lachnea Moure and Epicharis rustica Olivier touched stigmata and anthers more often. Fruit set and fruit weight per flower were significantly lower in the pollinator exclusion treatment compared to open and supplementary pollination, while the latter treatments showed nonsignificant differences. Pollination deficit significantly decreased with the increasing density of large bees and wasps. Our results illustrate the high dependency of granadilla on wild pollinating insects and highlight the crucial role of large insects to granadilla production. This stresses the need to maintain or increase the density of large pollinators in granadilla production areas, which in turn will necessitate better knowledge on their ecological requirements to inform landscape planning and population-management programs.

Exotic species enhance response diversity to land-use change but modify functional composition

Two main mechanisms may buffer ecosystem functions despite biodiversity loss. First, multiple species could share similar ecological roles, thus providing functional redundancy. Second, species may respond differently to environmental change (response diversity). However, ecosystem function would be best protected when functionally redundant species also show response diversity. This linkage has not been studied directly, so we investigated whether native and exotic pollinator species with similar traits (functional redundancy) differed in abundance (response diversity) across an agricultural intensification gradient. Exotic pollinator species contributed most positive responses, which partially stabilized overall abundance of the pollinator community. However, although some functionally redundant species exhibited response diversity, this was not consistent across functional groups and aggregate abundances within each functional group were rarely stabilized. This shows functional redundancy and response diversity do not always operate in concert. Hence, despite exotic species becoming increasingly dominant in human-modified systems, they cannot replace the functional composition of native species.

Forest bees are replaced in agricultural and urban landscapes by native species with different phenologies and life-history traits

Anthropogenic landscapes are associated with biodiversity loss and large shifts in species composition and traits. These changes predict the identities of winners and losers of future global change, and also reveal which environmental variables drive a taxon's response to land use change. We explored how the biodiversity of native bee species changes across forested, agricultural, and urban landscapes. We collected bee community data from 36 sites across a 75,000 km² region, and analyzed bee abundance, species richness, composition, and life-history traits. Season-long bee abundance and richness were not detectably different between natural and anthropogenic landscapes, but community phenologies differed strongly, with an early spring peak followed by decline in forests, and a more extended summer season in agricultural and urban habitats. Bee community composition differed significantly between all three land use types, as did phylogenetic composition. Anthropogenic land use had negative effects on the persistence of several life-history strategies, including early spring flight season and brood parasitism, which may indicate adaptation to conditions in forest habitat. Overall, anthropogenic communities are not diminished subsets of contemporary natural communities. Rather, forest species do not persist in anthropogenic habitats, but are replaced by different native species and phylogenetic lineages preadapted to open habitats. Characterizing compositional and functional differences is crucial for understanding land use as a global change driver across large regional scales.

Trap Nesting Wasps and Bees in Agriculture: A Comparison of Sown Wildflower and Fallow Plots in Florida

Wildflower strip plantings in intensive agricultural systems have become a widespread tool for promoting pollination services and biological conservation because of their use by wasps and bees. Many of the trap-nesting wasps are important predators of common crop pests, and cavity-nesting bees that utilize trap-nests are important pollinators for native plants and many crops. The impact of wildflower strips on the nesting frequency of trap-nesting wasps or bees within localized areas has not been thoroughly investigated. Trap-nests made of bamboo reeds (Bambusa sp.) were placed adjacent to eight 0.1 ha wildflower plots and paired fallow areas (control plots) to determine if wildflower strips encourage the nesting of wasps and bees. From August 2014 to November 2015, occupied reeds were gathered and adults were collected as they emerged from the trap-nests. Treatment (wildflower or fallow plots) did not impact the number of occupied reeds or species richness of trap-nesting wasps using the occupied reeds. The wasps Pachodynerus erynnis, Euodynerus megaera, Parancistrocerus pedestris, and Isodontia spp. were the most common trap-nesting species collected. Less than 2% of the occupied reeds contained bees, and all were from the genus Megachile. The nesting wasp and bee species demonstrated preferences for reeds with certain inside diameters (IDs). The narrow range of ID preferences exhibited by each bee/wasp may provide opportunities to take advantage of their natural histories for biological control and/or pollination purposes.

Crop pollination services at the landscape scale

Managed and wild pollinators of different functional groups can provide pollination services in agricultural landscapes. These pollinators differ in their resource requirements and response to the amount and arrangement of different habitat types, that is, landscape composition and configuration. Most current approaches to test landscape effects on pollinators and pollination services are either applied to central individual crop fields or other landscape elements but rarely consider that pollinators depend on and make use of multiple habitat elements in an entire landscape. To capture these complex spatial and temporal interactions between different pollinators and habitat elements at the landscape scale, we propose to apply a combination of experimental and observational approaches across multiple habitat types and seasons.

Floral Strips Attract Beneficial Insects but Do Not Enhance Yield in Cucumber Fields

Natural enemies and pollinators require nutritional and habitat resources that are often not found in conventional agricultural fields. The addition of flowering plants within agroecosystems may provide the resources necessary to support beneficial insects at the local scale. We hypothesized that insect pollinator and natural enemy abundance would increase in cucumber (Cucumis sativus) plots containing flower strips and that the effect would be greatest in the crop rows closest to the flower strips. Three flower treatments were tested: 1) buckwheat (Fagopyrum esculentum), 2) yellow mustard (Brassica hirta), 3) sweet alyssum (Lobularia maritima), and cucumbers as a control. Flowers were planted within a commercial cucumber field in 20-m-long strips in a randomized complete block design with six replications in the 2014 and 2015 growing seasons. Some floral treatments successfully attracted more beneficial insects than others, but the beneficials did not disperse out to the cucumber plants. Cucumber yield was unaffected by flowers with one exception: in 2015, cucumber yield in the sweet alyssum plots were greater than those in plots with no flowers. Our research indicates that adding flowers to cucumber fields to increase services from beneficial insects needs to be further investigated to better understand the effect of factors such as relative flowering strip size.

The Effects of Crop Intensification on the Diversity of Native Pollinator Communities

Increases in agricultural conversion are leading to declines in native grasslands and natural resources critical for beneficial insects. However, little is known regarding how these changes affect pollinator diversity. Land use types were categorized within 300 m and 3 km radii of pollinator sampling locations in Brookings County, SD. Pollinator abundance and species richness were regressed on the proportion of the landscape dedicated to row crops, grass and pasture, forage crops, small grains, and aquatic habitats using variance components modeling. Row crops had a negative effect on bee abundance at 300 m, after fixed effects modeling accounted for outliers skewing this relationship. At 3 km, corn positively affected bee abundance and richness, while soybean acreage decreased species richness. The landscape matrix of outlying sites consisted of large monocultured areas with few alternative habitat types available, leading to inflated populations of Melissodes and Halictidae. Syrphids had a positive parabolic relationship between diversity and row crops, indicating potential for competitive exclusion from intermediate landscapes. Unlike other studies, landscape diversity within 300 m was not found to significantly benefit pollinator diversity. Within especially agriculturally developed areas of the region, high abundances of pollinators suggest selection for a few dominant species. There was no effect of forage crops or aquatic habitats on pollinator diversity, indicating that less highly managed areas still represent degraded habitat within the landscape. Incorporating pollinator-friendly crops at the farm level throughout the region is likely to enhance pollinator diversity by lessening the negative effects of large monocultures.

Contrasting Pollinators and Pollination in Native and Non-Native Regions of Highbush Blueberry Production

Highbush blueberry yields are dependent on pollination by bees, and introduction of managed honey bees is the primary strategy used for pollination of this crop. Complementary pollination services are also provided by wild bees, yet highbush blueberry is increasingly grown in regions outside its native range where wild bee communities may be less adapted to the crop and growers may still be testing appropriate honey bee stocking densities. To contrast crop pollination in native and non-native production regions, we sampled commercial ‘Bluecrop’ blueberry fields in British Columbia and Michigan with grower-selected honey bee stocking rates (0–39.5 hives per ha) to compare bee visitors to blueberry flowers, pollination and yield deficits, and how those vary with local- and landscape-scale factors. Observed and Chao-1 estimated species richness, as well as Shannon diversity of wild bees visiting blueberries were significantly higher in Michigan where the crop is within its native range. The regional bee communities were also significantly different, with Michigan farms having greater dissimilarity than British Columbia. Blueberry fields in British Columbia had fewer visits by honey bees than those in Michigan, irrespective of stocking rate, and they also had lower berry weights and a significant pollination deficit. In British Columbia, pollination service increased with abundance of wild bumble bees, whereas in Michigan the abundance of honey bees was the primary predictor of pollination. The proportion of semi-natural habitat at local and landscape scales was positively correlated with wild bee abundance in both regions. Wild bee abundance declined significantly with distance from natural borders in Michigan, but not in British Columbia where large-bodied bumble bees dominated the wild bee community. Our results highlight the varying dependence of crop production on different types of bees and reveal that strategies for pollination improvement in the same crop can vary greatly across production regions.