Bee Community Composition Research Articles

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.

Harvesting effects on wild bee communities in bioenergy grasslands depend on nesting guild.

Conversion of annual crops to native perennial grasslands for bioenergy production may help conserve wild bees by enhancing nest and food resources. However, bee response to the disturbance of biomass harvesting may depend on their nesting location, thus their vulnerability to nest destruction, and the response of the forb community on which they forage. Moreover, because bees have long foraging ranges, effects of local harvesting may depend on the amount of natural habitat in the surrounding landscape. We performed a large-scale one- and two-year experiment in Michigan and Wisconsin, USA, respectively, to examine how grassland harvesting, landscape context, and study year affect the forb community, above- and belowground-nesting bee species richness, community composition, trap nest emergence, and visitation rate. In Wisconsin, harvesting increased forb richness, cover, and evenness compared to unharvested control sites. Harvesting negatively affected aboveground-nesting bee richness and emergence from trap nests, possibly because of nest destruction during the previous harvest. By contrast, harvesting positively affected belowground-nesting bee richness, possibly because of the greater food resource availability and reduced thatch allowing greater access to nesting sites in the soil. Harvesting also affected bee community composition, reflecting the increase in belowground-nesting species at harvested sites. Despite harvesting effects on forb and bee communities, there was no effect on flower visitation rate, indicating little effect on pollination function. We did not find a harvest by landscape context interaction, which, in combination with the negative harvesting effect on trap nest emergence, suggests that harvesting can affect local population growth rather than simply affecting forager aggregation in different resource environments. For bees, there was no harvest by study year interaction, indicating a consistent response over a short timescale. Similarly, in Michigan, belowground-nesting species also responded positively to harvesting, which was more pronounced in sandier soils that are preferred for nesting. However, other components of the Michigan bee and forb communities were not significantly affected by biomass harvesting. Overall, our study demonstrates that harvesting grasslands can positively affect the ~80% of bee species that nest belowground by enhancing nest and/or forage resources, but that conserving aboveground nesters may require leaving some area unharvested.

Minimal effect of honey beehive fences on native bee diversity and abundance at the farm scale during the dry season in southern Kenya

Beehive fences are an effective solution to resolve conflicts between humans and crop-raiding elephants in Kenya. They produce win-win scenarios; elephants are protected from aggression from humans as they are deterred from crop raiding, while farmers benefit from crop protection, pollination, and valuable products from maintaining honeybee hives. However, artificially increasing the density of these super-generalist pollinators in the landscape may impact wild bee species as honeybees may out-compete them for floral resources. We studied bee communities in Sagalla, Kenya, where beehive fences have been implemented for crop protection for many years. Despite the long-term presence of the beehive fences, honeybee densities were low when the study was conducted because of a severe drought and did not differ between beehive and control fences in our collections. When we compared farms with and without beehive fences, we found little difference in the abundance, species richness, and community composition of the resident wild bee communities. This suggests either (a) beehive fences have little permanent impact on wild bee communities, or (b) wild bee communities recover quickly when honeybee densities are low.

Different Physiognomies and the Structure of Euglossini bee (Hymenoptera: Apidae) Communities

Our aim was to evaluate the occurrence of orchid bees in remnants of the Atlantic Forest. We sampled specimens from five regions of Southeast Brazil, covering three different physiognomies of the Atlantic Forest (mixed Araucaria forests with high altitude fields, Atlantic Semi-deciduous Forest and Atlantic Rain Forest). The distances between the sampling sites ranged from 24 to 746 km. Male orchid bees attracted by fragrances were actively sampled monthly during one year using entomological nets and aromatic traps. A total of 1,482 bees were captured, including four genera and at least 31 species. We observed differences in the abundance and richness of species sampled among sites. Climatic variables, mostly relative humidity, explained twice more of the observed differences in the Euglossini communities than simple spatial variation. Our study found differences in the composition of euglossine bee communities as well as in their patterns of abundance and dominance among different vegetation formations. However, the level of pairwise similarity among the Euglossini communities sampled, although highly variable, was not related to climatic factors or geographical distances between the sampling sites. The greatest dissimilarities in the composition of the orchid bee communities were observed between sites around 400 km from each other rather than among sites that were further apart. A possible explanation is that the sampled areas that were 400 km from each other were also highly dissimilar regarding climate, especially altitude.

Effects of urbanisation and management practices on pollinators in tropical Africa

Abstract Urban expansion is an increasing threat to biodiversity, especially in tropical Africa where biodiversity hot spots are being encroached upon by fast‐growing cities. Threatened species include bees and other pollinators, which deliver important ecosystem services but are sensitive to land use changes. We investigated the impact of urbanisation and vegetation management practices on pollinator abundance, bee diversity, and bee functional traits. We sampled 126 locations in a stratified random design across an urbanisation gradient in two medium‐sized cities in the West African Forests biodiversity hot spot, encompassing three management practices (farmed sites; amenity lands, i.e. green spaces managed for aesthetics; informal green spaces), and tested their effect with generalised linear models. Urbanisation did not affect bee abundances or diversity but had a negative impact on both wasp and beetle abundances. There was also a management‐mediated impact of urbanisation on bee abundances, which decreased with urbanisation on farmed sites but not amenity land or informal green spaces. Management practices alone influenced bee abundances with farms harbouring fewer bees, and amenity lands fewer beetles. Bee genera occurrence and dominance patterns were influenced by both urbanisation and management, with some otherwise common genera rare in urban areas. Most functional traits were influenced by management, with fewer polylectic bees, cavity‐nesting bees and long‐tongued bees in farmed sites. Amenity lands hosted smaller bees and fewer savanna specialists. Some traits were influenced by urbanisation, with more long‐tongued bees and cavity‐nesting bees found in urban areas. Synthesis and applications. Pollinator responses to urbanisation are complex. In our research, we demonstrate how bee, lepidopteran, and non‐fruit fly abundances have been maintained across an urbanisation gradient in tropical Africa, but not wasp and beetle abundances. Moreover, bee community composition and the distribution of traits shifted markedly. How green spaces were managed was also critical. We found that farmed sites hosted the lowest bee abundances and amenity lands the fewest beetles. Retaining informal green spaces and amenity lands in African cities, including protecting nesting sites for stingless bees, and limiting pesticide application would be important for conserving bees and the pollination service they provide to both crops and native vegetation.

Restoration increases bee abundance and richness but not pollination in remnant and post‐agricultural woodlands

AbstractHuman land use, including agriculture, is a leading contributor to declining biodiversity worldwide and can leave long‐lasting legacies on ecosystems after cessation. Ecological restoration is an approach to mitigate these impacts. However, little is known about how animal communities and plant–animal interactions respond to the combined effects of land‐use legacies and restoration. We investigated how restoration and agricultural history affect bee (Hymenoptera: Apoidea: Anthophila) communities and pollination function. In 27 paired remnant (no history of agriculture) and post‐agricultural longleaf pine (Pinus palustrisMill.) woodlands, we established 4–10 1‐ha plots (126 total) and experimentally restored half of them, while the other half were left as unrestored controls. Restoration was accomplished through canopy thinning which reinstates open savanna‐like conditions. We collected bees in each plot using a combination of bowl trapping and standardized netting transects. Thinning increased bee abundance by 169% and bee richness by 110%, but agricultural land use had no effect on these variables. Bee community composition was affected by restoration and was marginally affected by agricultural history. To measure pollination function, we conducted a sentinel plant experiment in which potted black mustard (Brassica nigraL.) plants were placed out in a subset of these sites (n = 10) and either bagged to exclude pollinators or left open for pollinator access. Then, we measured fruit and seed set of sentinel plants to compare pollination function among the restoration and land‐use history treatments. Seed set and fruit set of sentinel plants were higher in open than bagged plants, indicating that this model system effectively measured pollination, but we found no differences in pollination based on restoration or agricultural history. These results indicate that although pollinator communities may show clear responses to restoration that are largely independent of prior land‐use impacts, this does not necessarily translate into differences in pollination function after restoration.

Unique Bee Communities within Vacant Lots and Urban Farms Result from Variation in Surrounding Urbanization Intensity

We investigated the relative importance of vacant lot and urban farm habitat features and their surrounding landscape context on bee community richness, abundance, composition, and resource use patterns. Three years of pan trap collections from 16 sites yielded a rich assemblage of bees from vacant lots and urban farms, with 98 species documented. We collected a greater bee abundance from vacant lots, and the two forms of greenspace supported significantly different bee communities. Plant–pollinator networks constructed from floral visitation observations revealed that, while the average number of bees utilizing available resources, niche breadth, and niche overlap were similar, the composition of floral resources and common foragers varied by habitat type. Finally, we found that the proportion of impervious surface and number of greenspace patches in the surrounding landscape strongly influenced bee assemblages. At a local scale (100 m radius), patch isolation appeared to limit colonization of vacant lots and urban farms. However, at a larger landscape scale (1000 m radius), increasing urbanization resulted in a greater concentration of bees utilizing vacant lots and urban farms, illustrating that maintaining greenspaces provides important habitat, even within highly developed landscapes.

Variation in the phylogenetic diversity of wild bees at produce farms and prairies

Declines in pollinators, particularly wild bees, along with rising demands for their services has intensified efforts to examine bee communities in different types of habitats. In this study we use a phylogenetic approach to compare and contrast bee communities associated with six small produce farms, eight large prairies, and five naturally small hill prairies in Iowa. We compare the mean phylogenetic distance (MPD) and the mean nearest taxon distance (MNTD) of bees in each community to expected mean MPD and MNTD values generated from 1000 random permutations of a tree composed of 144 species found across all sites. Standardized effect size scores for MPD using presence-absence data showed significant clustering of bee communities at five of six farms and two of the five hill prairies. Clustering at the farms and hill prairies was due primarily to the significantly lower number of species in the Andrenidae (0–5 species per site), especially species of Andrena, as well as significantly greater number of species in the Halictidae (9–22 species/site), particularly Lasioglossum (Dialictus). Lack of Andrenidae spp. may be related to a lack of appropriate floral resources, indicating that enriched prairie plantings for pollinators at farms could enhance the abundance of Andrena species and hence pollinator services at these sites. The higher richness of the ground-nesting Lasioglossum likely results from soil disturbance regimes at produce farms and the naturally shallow, rocky soil with exposed surface at hill prairies, respectively. Analyses of MNTD using either abundance weighted or presence-absence data and analyses of MPD using abundance data did not indicate consistent differences between the three site types, but do point to important differences between sites in phylogenetic composition of bee communities. Our results show that phylogenetic analyses of wild bee community diversity may be a useful tool for measuring how bee communities differ in composition as a result of natural variation and human-related changes in landscapes.

Predictability of bee community composition after floral removals differs by floral trait group.

Plant-bee visitor communities are complex networks. While studies show that deleting nodes alters network topology, predicting these changes in the field remains difficult. Here, a simple trait-based approach is tested for predicting bee community composition following disturbance. I selected six fields with mixed cover of flower species with shallow (open) and deep (tube) nectar access, and removed all flowers or flower heads of species of each trait in different plots paired with controls, then observed bee foraging and composition. I compared the bee community in each manipulated plot with bees on the same flower species in control plots. The bee morphospecies composition in manipulations with only tube flowers remaining was the same as that in the control plots, while the bee morphospecies on only open flowers were dissimilar from those in control plots. However, the proportion of short- and long-tongued bees on focal flowers did not differ between control and manipulated plots for either manipulation. So, bees within some functional groups are more strongly linked to their floral trait partners than others. And, it may be more fruitful to describe expected bee community compositions in terms of relative proportions of relevant ecological traits than species, particularly in species-diverse communities.

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 75,000km2 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.

Foraging traits modulate stingless bee community disassembly under forest loss.

Anthropogenic land use change is an important driver of impacts to biological communities and the ecosystem services they provide. Pollination is one ecosystem service that may be threatened by community disassembly. Relatively little is known about changes in bee community composition in the tropics, where pollination limitation is most severe and land use change is rapid. Understanding how anthropogenic changes alter community composition and functioning has been hampered by high variability in responses of individual species. Trait-based approaches, however, are emerging as a potential method for understanding responses of ecologically similar species to global change. We studied how communities of tropical, eusocial stingless bees (Apidae: Meliponini) disassemble when forest is lost. These bees are vital tropical pollinators that exhibit high trait diversity, but are under considerable threat from human activities. We compared functional traits of stingless bee species found in pastures surrounded by differing amounts of forest in an extensively deforested landscape in southern Costa Rica. Our results suggest that foraging traits modulate competitive interactions that underlie community disassembly patterns. In contrast to both theoretical predictions and temperate bee communities, we found that stingless bee species with the widest diet breadths were less likely to persist in sites with less forest. These wide-diet-breadth species also tend to be solitary foragers, and are competitively subordinate to group-foraging stingless bee species. Thus, displacement by dominant, group-foraging species may make subordinate species more dependent on the larger or more diversified resource pool that natural habitats offer. We also found that traits that may reduce reliance on trees-nesting in the ground or inside nests of other species-correlated with persistence in highly deforested landscapes. The functional trait perspective we employed enabled capturing community processes in analyses and suggests that land use change may disassemble bee communities via different mechanisms in temperate and tropical areas. Our results further suggest that community processes, such as competition, can be important regulators of community disassembly under land use change. A better understanding of community disassembly processes is critical for conserving and restoring pollinator communities and the ecosystem services and functions they provide.

Assessing Wild Bee Biodiversity in Cranberry Agroenvironments: Influence of Natural Habitats.

The conservation of bee populations for pollination in agricultural landscapes has attracted a lot of recent research interest, especially for crop industries undergoing expansion to meet increased production demands. In Canada, much growth has been occurring with commercial cranberry production, a field crop which is largely dependent on bee pollination. Wild bee pollinators could be negatively impacted by losses of natural habitat surrounding cranberry fields to accommodate increased production, but growers have little insight on how to manage their lands to maximize the presence of wild bees. Here, we described a 2-yr study where bee diversity and species composition were investigated to better understand the dynamic between natural habitat and cranberry fields. Bees were sampled using pan-traps and hand netting both within cranberry fields and in one of the three adjacent natural habitat types once a week during the crop flowering period. We found that bee community composition among cranberry fields did not differ based on the respective adjacent habitat type, but fields bordered by meadows were marginally less diverse than fields bordered by forest. As one would expect, field and natural habitat communities differed in terms of species composition and species richness. There was no evidence that one type of natural habitat was more favorable for the bees than another. Future agrobiodiversity studies should simultaneously examine bee diversity comprised in both crop fields and adjacent natural environments to better understand the species dynamics essential to the preservation of pollination services.

Wild bee community change over a 26‐year chronosequence of restored tallgrass prairie

AbstractRestoration efforts often focus on plants, but additionally require the establishment and long‐term persistence of diverse groups of nontarget organisms, such as bees, for important ecosystem functions and meeting restoration goals. We investigated long‐term patterns in the response of bees to habitat restoration by sampling bee communities along a 26‐year chronosequence of restored tallgrass prairie in north‐central Illinois, U.S.A. Specifically, we examined how bee communities changed over time since restoration in terms of (1) abundance and richness, (2) community composition, and (3) the two components of beta diversity, one‐to‐one species replacement, and changes in species richness. Bee abundance and raw richness increased with restoration age from the low level of the pre‐restoration (agricultural) sites to the target level of the remnant prairie within the first 2–3 years after restoration, and these high levels were maintained throughout the entire restoration chronosequence. Bee community composition of the youngest restored sites differed from that of prairie remnants, but 5–7 years post‐restoration the community composition of restored prairie converged with that of remnants. Landscape context, particularly nearby wooded land, was found to affect abundance, rarefied richness, and community composition. Partitioning overall beta diversity between sites into species replacement and richness effects revealed that the main driver of community change over time was the gradual accumulation of species, rather than one‐to‐one species replacement. At the spatial and temporal scales we studied, we conclude that prairie restoration efforts targeting plants also successfully restore bee communities.

The Impact of Different Phytophysiognomies on the Composition of Orchid Bee Communities (Hymenoptera: Apidae: Euglossini) in the Atlantic Forest in Brazil

We sampled bees of the tribe Euglossini in three close areas within a small region of Sao Paulo state that includes three different phytophysiognomies of the Atlantic Forest biome. Even though Euglossini bees are known for flying great distances, there were clear differences in the composition of bee communities, including differences in abundance and richness of species at specific points within the same biome. The area characterized by tropical rainforest was the richest in bee fauna of this group, followed by the mixed rainforest area, whereas no specimens of Euglossini were found in nearby high-altitude fields. The differences in composition and abundance of orchid bees in geographically close areas reveal the importance of the conservation of distinct habitat patches within a biome for bee conservation.

Landscape structure influences bee community and coffee pollination at different spatial scales

Although several studies have shown that the presence of bees results in increased crop yields, the mechanisms that determine pollination service across different spatial scales are still largely unknown. Here, we evaluated the influence of landscape structure over bee community composition and coffee (Coffea arabica) pollination. Our study was undertaken in one of the most important coffee-producing regions of Brazil, and comprised nine landscapes of sun coffee plantations surrounded by different amounts of Atlantic Forest remnants. Using floral exclusion experiments we evaluated fruit set in 15 coffee shrubs per landscape. We also sampled the bees visiting coffee flowers. Our analyses were made at two landscape scales, with 1 and 2km radii, and one shrub scale, with 300m radius around each coffee shrub. We collected 241 bee individuals and identified a total of 22 species. The honeybee Apis mellifera (Apini) was the most abundant flower visitor followed by Trigona spinipes (Meliponini). Native bee abundance, richness and diversity were positively affected by forest cover at the shrub scale. Honeybee abundance, on the other hand, was negatively affected by forest cover at the shrub scale. The presence of bees resulted in an increase in coffee fruit set of 28%. A. mellifera abundance positively affected fruit set across spatial scales, while the composition of the native bee community affected fruit set differently at the landscape scales than at the shrub scale. Our work shows that bee pollination services are affected by landscape structure at different spatial scales. These findings can be used in conservation and agricultural planning to maximize crop production while safeguarding biodiversity and the provision of pollination services.

Land use change and pollinator extinction debt in exurban landscapes

Abstract For the first time in more than a century, people across the planet are migrating en mass from cities to rural areas. In this process of ‘exurbanisation’ humans are rapidly converting natural and agricultural regions into low‐density housing. Despite the scale of this exurban development and its potential negative impact on biodiversity, little is known about how this specific type of land conversion impacts wild pollinators. In this study, we conduct an extensive survey of the wild pollinators of the peach agroecosystem and investigate the impact of current and historic land use at multiple spatial scales on pollinator community composition within agroecological landscapes that have recently undergone exurban development. We reveal that the overall composition of the wild pollinator community is significantly associated with current local agricultural and natural land cover. Specifically, local agricultural land use was associated with ground‐nesting bee community composition, whereas natural lands were associated with cavity‐nesting bee composition, revealing that nesting materials drive community composition for these two groups in exurban habitats. In contrast, community composition for butterflies and flies, which made up the smallest proportion of our communities, were not strongly associated with any particular land use type, likely due to their non‐central place foraging strategy. Most interestingly, our results indicate that historic land use remains a significant factor impacting the current abundance of all pollinators in the peach agroecosystem, offering the first evidence of extinction debt in this rapidly expanding exurban landscape.

The challenge of accurately documenting bee species richness in agroecosystems: bee diversity in eastern apple orchards.

Bees are important pollinators of agricultural crops, and bee diversity has been shown to be closely associated with pollination, a valuable ecosystem service. Higher functional diversity and species richness of bees have been shown to lead to higher crop yield. Bees simultaneously represent a mega-diverse taxon that is extremely challenging to sample thoroughly and an important group to understand because of pollination services. We sampled bees visiting apple blossoms in 28 orchards over 6 years. We used species rarefaction analyses to test for the completeness of sampling and the relationship between species richness and sampling effort, orchard size, and percent agriculture in the surrounding landscape. We performed more than 190 h of sampling, collecting 11,219 specimens representing 104 species. Despite the sampling intensity, we captured <75% of expected species richness at more than half of the sites. For most of these, the variation in bee community composition between years was greater than among sites. Species richness was influenced by percent agriculture, orchard size, and sampling effort, but we found no factors explaining the difference between observed and expected species richness. Competition between honeybees and wild bees did not appear to be a factor, as we found no correlation between honeybee and wild bee abundance. Our study shows that the pollinator fauna of agroecosystems can be diverse and challenging to thoroughly sample. We demonstrate that there is high temporal variation in community composition and that sites vary widely in the sampling effort required to fully describe their diversity. In order to maximize pollination services provided by wild bee species, we must first accurately estimate species richness. For researchers interested in providing this estimate, we recommend multiyear studies and rarefaction analyses to quantify the gap between observed and expected species richness.

Emulating natural disturbance in forest management enhances pollination services for dominant Vaccinium shrubs in boreal pine-dominated forests

Lack of natural disturbances and the homogenization of boreal forest because of intensive forest management pose a threat to biodiversity and can endanger the provision of ecosystem services. In this study, we assessed how two methods aimed to promote biodiversity, i.e. prescribed fire and retention forestry (RET), affect ecosystem services supported by bilberry and lingonberry in Scots pine-dominated boreal forests. Shrub cover, flowering, berry yield and percent fruit set of both shrubs were measured and bees were sampled by pan-traps on 24 study sites 13years following a large-scale experiment, where RET (0, 10, 50m3/ha and uncut forests) and fire (yes/no) were manipulated following a replicated factorial design. In general, bilberry performance and reproduction were higher at uncut sites, while lingonberry flowering was positively affected by fire and retention. Bee community composition was mainly determined by percentage of bare ground and number of logs within sites, both nesting resources largely determined by fire and retention. Burnt sites with retention trees serve as pollinator source habitats and contain floral resources, highlighting the importance of natural disturbances and biological legacies in the conservation of pollination services from boreal forests.

Modeling pollinator community response to contrasting bioenergy scenarios.

In the United States, policy initiatives aimed at increasing sources of renewable energy are advancing bioenergy production, especially in the Midwest region, where agricultural landscapes dominate. While policy directives are focused on renewable fuel production, biodiversity and ecosystem services will be impacted by the land-use changes required to meet production targets. Using data from field observations, we developed empirical models for predicting abundance, diversity, and community composition of flower-visiting bees based on land cover. We used these models to explore how bees might respond under two contrasting bioenergy scenarios: annual bioenergy crop production and perennial grassland bioenergy production. In the two scenarios, 600,000 ha of marginal annual crop land or marginal grassland were converted to perennial grassland or annual row crop bioenergy production, respectively. Model projections indicate that expansion of annual bioenergy crop production at this scale will reduce bee abundance by 0 to 71%, and bee diversity by 0 to 28%, depending on location. In contrast, converting annual crops on marginal soil to perennial grasslands could increase bee abundance from 0 to 600% and increase bee diversity between 0 and 53%. Our analysis of bee community composition suggested a similar pattern, with bee communities becoming less diverse under annual bioenergy crop production, whereas bee composition transitioned towards a more diverse community dominated by wild bees under perennial bioenergy crop production. Models, like those employed here, suggest that bioenergy policies have important consequences for pollinator conservation.