Bee Assemblages Research Articles

Contrasting effects of natural shrubland and plantation forests on bee assemblages at neighboring apple orchards in Beijing, China

Wild bees provide important pollination services for crops and wild plants. While land use intensification has resulted in steep declines of wild bee diversity across agricultural landscapes, the creation of semi-natural habitats has been proposed as a counter-measure. However, the relative value of semi-natural and natural habitats in promoting wild bees has rarely been studied, especially for China that harbors the world's largest plantation forest area, characterized by intensively managed, mono-dominant stands of wind-pollinated tree species. We sampled wild bees in apple orchards to assess how their assemblages were influenced by semi-natural habitats in the surrounding landscape and the local flowering ground-cover. Bee abundance declined with increasing isolation from natural shrubland. In contrast, wild bee diversity and abundance were negatively linked to plantation forests. For the abundance of large bees, this effect was partly ameliorated by local flowering ground-cover. Maintaining or restoring wild bee assemblages in agricultural landscapes therefore requires careful evaluations of restoration measures such as forest planting. Availability of local flower resources and nearby natural shrubland appeared particularly important to enhance wild bees and their potential services in apple orchards.

Pollinators on the polar edge of the Ecumene: taxonomy, phylogeography, and ecology of bumble bees from Novaya Zemlya.

The High Arctic bumble bee fauna is rather poorly known, while a growing body of recent molecular research indicates that several Arctic species may represent endemic lineages with restricted ranges. Such local endemics are in need of special conservation efforts because of the increasing anthropogenic pressure and climate changes. Here, we re-examine the taxonomic and biogeographic affinities of bumble bees from Novaya Zemlya using historical samples and recently collected materials (1895–1925 vs. 2015–2017). Three bumble bee species inhabit the Yuzhny (Southern) Island and the southern edge of Severny (Northern) Island of this archipelago: Bombusglacialis Friese, 1902, B.hyperboreus Schönherr, 1809, and B.pyrrhopygus Friese, 1902. Bombusglacialis shares three unique COI haplotypes that may indicate its long-term (pre-glacial) persistence on Novaya Zemlya. In contrast, Bombushyperboreus and B.pyrrhopygus share a rather low molecular divergence from mainland populations, with the same or closely related haplotypes as those from Arctic Siberia and Norway. A brief re-description of Bombuspyrrhopygus based on the newly collected topotypes is presented. Habitats, foraging plants and life cycles of bumble bees on Novaya Zemlya are characterized, and possible causes of extremely low bumble bee abundance on the archipelago are discussed. The species-poor bumble bee fauna of Novaya Zemlya is compared with those in other areas throughout the Arctic. The mean bumble bee species richness on the Arctic Ocean islands is three times lower than that in the mainland Arctic areas (3.1 vs. 8.6 species per local fauna, respectively). General linear models (GLMs) indicate that this difference can be explained by specific environmental conditions of insular areas. Our findings highlight that the insularity is a significant factor sharply decreasing species richness in bumble bee assemblages on the Arctic Ocean archipelagoes through colder climate (lower summer temperatures), prevalence of harsh Arctic tundra landscapes with poor foraging resources, and in isolation from the mainland.

No Vertical Stratification Found in Cavity-Nesting bees and Wasps in Two Neotropical Forests of Argentina.

Vertical stratification is known in diverse arthropod communities in forests, but little is known about nesting ecology of trap-nesting bees and wasps in Neotropical forests. We studied the vertical colonization of trap-nests by solitary bees and wasps in two forests in Argentina. We obtained 204 nests of seven bee and six wasp species, with 1040 brood cells from which 660 hosts and 32 parasites (21 parasitoid and 11 kleptoparasite) adults emerged from four groups (five species of wasps [Chrysididae, Eulophidae, and Ichneumonidae], four flies [Bombyliidae and Sarcophagidae], three bees [Apidae and Megachilidae], and one species of beetle [Meloidae]). The number of nests, reproductive success, parasitism rate, and mortality did not differ between canopy and understory, nor did the number of brood cells, emerged adults per trap-nest, and total abundance per transect. We found similar assemblages of trap-nesting bees and wasps in both forests, but contrary to our expectations, we did not find any significant difference in the analyzed variables. Our results suggest that access to resources used by trap-nesting bee and wasp females was at least similar, and/or that the microclimatic conditions were homogeneous in canopy and understory. Moreover, our results agree with those reported by some researchers but contrast with others, demonstrating the great variation in the response of bees and wasps nesting in preexisting cavities to vertical stratification in forests and the need for more studies about this topic.

Ecological filtering in scrub fragments restructures the taxonomic and functional composition of native bee assemblages.

Predicting the long-term consequences of habitat alteration for the preservation of biodiversity and ecosystem function requires an understanding of how ecological filters drive taxonomic and functional biodiversity loss. Here, we test a set of predictions concerning the role of ecological filters in restructuring native bee assemblages inhabiting fragmented coastal sage scrub ecosystems in southern California, USA. In 2011 and 2012, we collected native bees in scrub habitat belonging to two treatment categories: large natural reserves and small habitat fragments embedded in an urban landscape. We compared bee assemblages in reserve and fragment sites with respect to their taxonomic and functional alpha diversity, beta diversity, assemblage composition, and mean geographical range size estimated via distribution maps compiled for this study from digitized specimen records. We found multiple lines of evidence that ecological filtering drove bee diversity loss in fragments: a disproportionate loss of functional diversity relative to taxonomic diversity, shifts in assemblage composition driven largely by the preferential extirpation of reserve-associated indicator species, and disproportionate loss of range-restricted species. However, we found no evidence of taxonomic or functional homogenization across fragment bee assemblages, suggesting that filtering was not sufficiently strong to cause a subset of functional traits (and their associated species) to dominate assemblages in fragments. Our results suggest that ecological filtering altered bee assemblages in habitat fragments, even when such fragments contained well-preserved native plant assemblages, underscoring the importance of preserving large areas of natural habitat for the conservation of bees (especially range-restricted taxa) and their associated ecological functions.

Explaining the birds and the bees: deriving habitat restoration targets from multi‐species occupancy models

AbstractRiparian corridors can be highly biodiverse but are often degraded by human activities, and are therefore frequent targets of restoration actions. Yet managers often lack clear guidance on how to conserve or restore riparian vegetation structure and composition to promote wildlife biodiversity, due to the difficulty of balancing the needs of multiple species and taxonomic groups. We used independent multi‐species occupancy models to assess the response of riparian bird and bumble bee assemblages, respectively, to variation in vegetation structure and composition in montane riparian corridors. We sought to identify vegetation characteristics associated with relatively high richness across each taxonomic group to define target conditions for habitat restoration. Riparian bird occupancy increased with more willow (Salixspp.) cover and less overstory cover, while bumble bee occupancy increased with greater flowering plant richness, more forb cover, and less shrub cover. Relatively distinct habitat preferences of bumble bees and riparian birds emphasize the value of managing for habitat heterogeneity to promote biodiversity across multiple taxonomic groups. Multi‐species modeling distills the responses of numerous species down to a single estimate of a covariate effect for an assemblage of species and can provide land managers with empirically derived targets for habitat restoration that will benefit many species.

Historical records of orchid bees (Apidae: Euglossini) in Belém Endemism Center: species list of 92 years sampling.

The distribution of most species occurs in delimited regions with unique characteristics called "centers of endemism". In Eastern Amazon is located the Belém Endemism Center (BEC), one of the most intensely deforested in Brazilian Amazon. Here, we show information about orchid bee assemblages based on historical records from entomological collections. For each species, we calculated occurrence frequency and dominance, and we classified them in 3 statuses: common, intermediate or rare species. Curves of observed and estimated richness were built, based on Jackknife estimator. We found 1,257 specimens from 56 species, constituting records from 1917 to 2009, and one species is a new record for BEC. Higher number of specimens and species was concentrated in a few locations and surveys increased from the 70's. The results suggest a high richness of orchid bees in the BEC, although this scenario is far from what is expected for the entire area. The high occurrence of rare species may be related to their low representativeness in the collections, and the proximity between the areas had favored samplings. Even so, the species list and the conservation status presented here may be useful information in studies comparing past and current orchid bee fauna, and, allied to data on bees' responses to land use changes occurred in BEC over the years, can fit as a basis for defining priority areas for conservation.

Quantifying bee assemblages and attractiveness of flowering woody landscape plants for urban pollinator conservation.

Urban and suburban landscapes can be refuges for biodiversity of bees and other pollinators. Public awareness of declining pollinator populations has increased interest in growing plants that provide floral resources for bees. Various publications and websites list “bee-friendly” plants, but such lists are rarely based on empirical data, nor do they emphasize flowering trees and shrubs, which are a major component of urban landscapes. We quantified bee visitation to 72 species of flowering woody landscape plants across 373 urban and suburban sites in Kentucky and southern Ohio, USA, sampling and identifying the bee assemblages associated with 45 of the most bee-attractive species. We found strong plant species effects and variation in seasonal activity of particular bee taxa, but no overall differences in extent of bee visitation or bee genus diversity between native and non–native species, trees and shrubs, or early-, mid-, and late-season blooming plants. Horticulturally-modified varieties of Hydrangea, Prunus, and Rosa with double petals or clusters of showy sterile sepals attracted few bees compared to related plants with more accessible floral rewards. Some of the non-native woody plant species bloomed when floral resources from native plants were scarce and were highly bee-attractive, so their use in landscapes could help extend the flowering season for bees. These data will help city foresters, landscape managers, and the public make informed decisions to create bee–friendly urban and suburban landscapes.

The effect of adjacent habitat on native bee assemblages in a perennial low-input agroecosystem in a semiarid anthropized landscape

The decline of pollination services in some regions has stimulated much research on the effects of agricultural intensification on bees. In addition to the characteristics of agricultural plots, bee assemblages in them are influenced by the adjacent habitats. Perennial, fruit-oriented nopal (Opuntia spp.) orchards cover large surfaces in Mexico, North Africa, South America and southern U.S.A. and produce tens of thousands of flowers, but their value as habitat for bees was unknown. To document bee assemblages in nopal orchards in the Llanos de Ojuelos, southern Mexican Plateau, and to assess the influence of adjacent habitats on them, we surveyed bees in nopal orchards adjacent to cropland (Cr-orchards) and adjacent to natural shrubland patches (Sh-orchards), and in remnants of natural shrubland. We used color traps and manual capture from flowers during the 2016 and 2017 peaks of Opuntia blooming periods. We hypothesized that Sh-orchards would harbor richer and larger native bee assemblages than Cr-orchards, and that assemblages´ similarity between these Sh-orchards and shrublands would be greater than between Cr-orchards and shrublands. We collected 3823 individuals of 45 different bee taxa; 90% of all taxa, in nopal orchards. Our results partially support the premise that proximity of natural habitats to agricultural plots is positive for their bee overall abundance, but distance from shrublands did not impoverish bee species richness. Mean similarity values between Cr-orchards, Sh-orchards, and shrublands were not significantly different, as result of shrubland patches being very variable. As a result of their perennial condition and limited agricultural practices, nopal orchards provide shelter, forage, and nest substrate for native bee species, albeit perhaps less in Cr-orchards than in Sh-orchards, and likely facilitate bee movement between orchards and, or shrublands through a matrix of annual croplands. In doing so, this agroecosystem enhances regional bee community resilience in the context of an anthropized landscape.

Along urbanization sprawl, exotic plants distort native bee (Hymenoptera: Apoidea) assemblages in high elevation Andes ecosystem.

Native bees contribute a considerable portion of pollination services for endemic as well as introduced plant species. Their decline has been attributed to several human-derived influences including global warming as well as the reduction, alteration, and loss of bees’ habitat. With human expansion comes along the introduction of exotic plant species with negative impacts over native ecosystems. Anthropic effects may even have a deeper impact on communities adapted to extreme environments, such as high elevation habitats, where abiotic stressors alone are a natural limitation to biodiversity. Among these effects, the introduction of exotic plants and urbanization may have a greater influence on native communities. In this work, we explored such problems, studying the relationship between the landscape and its effect over richness and abundance of native bees from the subandean belt in the Andes mountain chain. Furthermore, we investigated the effects of exotic plant abundance on this high-altitude bee assemblage. Despite the landscape not showing an effect over bee richness and abundance, exotic plants did have a significant influence over the native bee assemblage. The abundance of exotic plants was associated with a relative increase in the proportion of small and medium bee species. Moreover, Halictidae was the only family that appeared to be favored by an increase in the abundance of exotic plant species. We discuss these results and the urgent need for further research of high-altitude environments due to their vulnerability and high endemicity.

Wild bees of Grand Staircase-Escalante National Monument: richness, abundance, and spatio-temporal beta-diversity.

Interest in bees has grown dramatically in recent years in light of several studies that have reported widespread declines in bees and other pollinators. Investigating declines in wild bees can be difficult, however, due to the lack of faunal surveys that provide baseline data of bee richness and diversity. Protected lands such as national monuments and national parks can provide unique opportunities to learn about and monitor bee populations dynamics in a natural setting because the opportunity for large-scale changes to the landscape are reduced compared to unprotected lands. Here we report on a 4-year study of bees in Grand Staircase-Escalante National Monument (GSENM), found in southern Utah, USA. Using opportunistic collecting and a series of standardized plots, we collected bees throughout the six-month flowering season for four consecutive years. In total, 660 bee species are now known from the area, across 55 genera, and including 49 new species. Two genera not previously known to occur in the state of Utah were discovered, as well as 16 new species records for the state. Bees include ground-nesters, cavity- and twig-nesters, cleptoparasites, narrow specialists, generalists, solitary, and social species. The bee fauna reached peak diversity each spring, but also experienced a second peak in diversity in late summer, following monsoonal rains. The majority of GSENM’s bees are highly localized, occurring in only a few locations throughout the monument, and often in low abundance, but consistently across the four years. Only a few species are widespread and super-abundant. Certain flowering plants appear to be inordinately attractive to the bees in GSENM, including several invasive species. GSENM protects one of the richest bee faunas in the west; the large elevational gradient, incredible number of flowering plants, and the mosaic of habitats are all likely contributors to this rich assemblage of bees.

Impact of inundation regime on wild bee assemblages and associated bee–flower networks

Wild bee assemblages on flood-prone meadows were compared with those on rarely inundated sites along the river Danube in easternmost Lower Austria. We sampled flower-visiting bees on 32 meadows from April to August 2016. Although we recorded more bee individuals on rarely inundated meadows, total bee species richness was higher on regularly flooded meadows and we observed a stronger differentiation diversity of bees among annually flooded meadows. Three network metrics derived from a bipartite plant–bee interaction matrix were unaffected by flooding regime. We conclude that extreme floods, which sporadically affect the investigated habitats, may have a devastating effect on wild bee populations, but communities quickly recover. This resilience surely depends on recolonization from the surrounding landscape, which emphasizes the need to consider community dynamics in highly variable floodplain areas not only locally, but on a landscape scale.

Tiny fragments of acidophilous steppic grasslands serve as yet unknown habitats of endangered aeolian sand specialists among Aculeata (Hymenoptera)

Aeolian sand specialists are traditionally recognized among the most threatened species of central European landscapes due to habitat loss. In the present study, we examined the diversity of bees and wasps, and the cover and composition of vegetation in 17 neglected small fragments of Artemisio campestris–Corynephoretum canescentis acidophilous grasslands, which developed on weathered granodiorite rocks in the Czech Republic. The size of the examined fragments ranged from 128 to 14,000 m2, with a total area of only 5.7 ha. At the examined sites, we identified species-rich assemblages of endangered aculeate hymenopterans that were previously thought to be specialized on aeolian sands. We found that despite the small area and relative isolation of the examined sites, they hosted 26 Red-Listed species of bees and wasps and a species new to Bohemia (Megachile pilicrus), respectively. The examined habitats also supported the presence of 18 Red-Listed receding field weeds and steppic grassland specialists. The analyzed bee and wasp assemblages were characterized by their low dominance (1-Simpson index = 0.091) and high alpha diversity (Fisher’s alpha = 48.9). Although the examined fragments of acidophilous steppic grasslands differed in size by two orders of magnitude, the total abundance and species richness of the bees and wasps were not correlated with the size of the fragments. This suggests the long-term stability despite the minute size of some of the residual fragments. Land protection and active management are proposed to conserve these habitats for future generations.

Species Richness and Diversity in Bee Assemblages in a Fragment of Savanna (Cerrado) at Northeastern Brazil

The conservation of the fauna of bees inhabiting the Brazilian savanna is threatened due to changes in land use in the last decades. We investigated the composition, species richness and abundance of a bee assemblage in the vicinity of the Chapada Diamantina National Park. In addition, we compiled data on composition and diversity from another bee assemblage located in the same portion of the Cerrado, which was previously investigated by one of us almost 30 years ago, in order to produce a more complete panorama on beta diversity of bees in this region. We used a non-metric multidimensional scaling ordination analysis (NMDS) to compare composition of bee assemblages from diff erent types of open vegetation. We recorded 77 bee species (H’ = 2.95; J = 0.68), 42% of them were singletons. We collected slightly more than half of the species and 60% of the genera recorded in the bee assemblage studied three decades ago. H’ was signifi cantly lower in our area than in the previous study (t = 8.588, p <0.001), but equitability (J) was very similar. Several factors may contribute to these diff erences, including local diff erences in bee assemblage composition, diff erences in the probability of capturing the diff erent species (many rare species), factors affecting the sampling itself, and perhaps species loss over the three decades separating the two studies. The magnitude of species loss is difficult to assess because the two studies were not carried out exactly in the same area and there were differences in sampling time and sampling effort.

Floral Traits and Foraging Behavior of the Bee Assemblage Visiting Martynia annua L. (Martyniaceae) in Coastal Jalisco, Mexico

Floral visitors are often overlooked in those plants considered invasive and widespread weed species. Martynia annua L. is an example of an introduced species to the old world being native from tropical America, however, information of its endemic pollinators in the Neotropical region is missing. In this study, the floral visitors of M. annua were evaluated in Chamela Field Station (Chamela-Cuixmala Biosphere Reserve) in Jalisco, Mexico. Our aim was to provide information of the breeding system of M. annua and then indicate the potential pollinators. We included morphological and sexual features to estimate the outcrossing index (OCI). The frequency, behavior, and pollen loads were considered to find the potential pollinator. Despite the evidence of protandry and OCI indicating a xenogamous breeding system, the lack of herkogamy suggests M. annua is a facultative xenogamous species. The highest frequency of visits corresponded to the maximum diameter of corolla. Euglossa viridissima was the most recurrent visitor. However, this species often carried a high proportion of heterospecific pollen and did not touch any sexual structure of the flower. In contrast, Centris agilis performed as the most likely pollinator. Flowers of M. annua offer valuable rewards to its visitors and may be a good source of energy to those foragers capable of reaching the nectaries, though small bees are apparently unable to penetrate the flowers. We consider that there are evidence that suggests M. annua is a specialized melittophilic plant, pollinated by moderate to large-sized hairy bees throughout its distribution.

Influence of Wild Bee Diversity on Canola Crop Yields

The foraging range of bees determines the spatial scale over which each species can provide pollination services. In agricultural ecosystems, productivity is related not only to the taxonomic diversity of bees per se, but also to the location of their nesting sites, which reflects on their flying range. Within this context, the present study sought to assess how wild bee assemblages affect the yield of Brassica napus at three different distances (25 m, 175 m, 325 m) from forest remnants in Southern Brazil. Bees were sampled by means of pan traps and findings were analyzed using the Shannon diversity index and generalized linear models. We identified 11 species of native bees, both solitary and social, as well as the exotic species Apis mellifera, which was most abundant. Our findings show that canola crop yield were positively influenced by the diversity of bee species. This demonstrates that native bees, not only A. mellifera, can contribute significantly to the productivity of canola crops. In addition, we found that bee body size is significantly associated with flight distance traveled within the canola fields, and demonstrated a relationship with nesting sites. Thus, we hypothesize that canola yields are associated with the presence of wild bee species, both social and solitary, and that maintenance of these pollinators is directly dependent on practices adopted in rural areas, whether within plantation fields per se or in forest remnants used as nesting sites by wild bees.

Bee Assemblages in Managed Early-Successional Habitats in Southeastern New Hampshire

We examined the abundance and species richness of bees at 10 sites managed for Sylvilagus transitionalis (New England Cottontail Rabbit) in southeastern New Hampshire. In 2015, we sampled bees using a streamlined bee-monitoring protocol (SBMP) developed for rapid assessment of bee communities, and in 2015 and 2016, we employed bee bowls (modified pan traps) painted fluorescent blue, yellow, or white and filled and with soapy water that were intended to mimic flower colors and attract bees. We compared the abundance of all species combined and species richness among management treatments (clearcuts, old fields, and gravel pits), patch area, and time since management action. We also compared the combined captures from bee bowls to relative abundance indices from the SBMP, as well as flower abundance and richness. Neither captured bee abundance nor species richness differed among management treatments; however, by removing a possible outlier, both abundance and richness were greatest in gravel pits compared to other habitats. There was no correlation between bee captures and the SBMP, and no correlation between captures and flower abundance or floral diversity. Our study demonstrates that habitats managed for New England Cottontail support a diverse assemblage of native bees. Gravel pits are potentially valuable targets for native bee conservation, but old fields and clearcuts offer alternatives in landscapes without gravel pits. Native bees are essential to support ecosystem function, and understanding their distribution and natural history is important to develop habitatmanagement efforts that benefit not only bees but multiple species of conservation concern within early-successional habitats.

Climate and habitat influences on bee community structure in Western Canada

The persistence of pollinators in a given habitat is determined in part by traits that affect their response to environmental variables. Here, we show that climate and habitat features are the main drivers of trait distribution in bees across spatially separated habitats. We determined that trait and clade filtering results in bee assemblages in Western Canada exhibiting clustering that is correlated with differences in temperature, humidity, and rainfall. Phylogenetic signals were detected in all traits associated with pollinator life-history strategies, including phenology. The Bombus Latreille, 1802 clade (including the social parasite subgenus Psithyrus Lepeletier, 1833) comprised a higher proportion of prairie bees, whereas assemblages in Garry oak sites exhibited higher representation from solitary bees (e.g., genera Osmia Panzer, 1806, Andrena Fabricius, 1775, Ceratina Latreille, 1802). Because these same traits influence which plant species are pollinated, this selective environmental occupancy within the two different habitats could promote local adaptation of flowering plant species pollinated by more social clades in prairies and more solitary bees in Garry oak.

Wild bees respond complementarily to ‘high-quality’ perennial and annual habitats of organic farms in a complex landscape

Agricultural intensification leads to large-scale loss of habitats offering food and nesting sites for bees. This has resulted in a severe decline of wild bee diversity and abundance during the past decades. There is an urgent need for cost-effective conservation measures to mitigate this decline. We analysed the impact of five different high-quality habitats on species richness and abundance of wild bees in a complex landscape of north-western Switzerland at six sites. The five habitat types included 45 plots situated on eight organic farms and were composed of 16 low-input meadows, six low-input pastures, seven herbaceous strips adjacent to hedges, five sown flower strips and eleven organic cereal fields. All of them are financially subsidised by the Swiss agri-environmental scheme. Wild bees were sampled between the end of April and end of August 2014 by using trio-pan traps and complementary sweep netting on these five habitat types. On 45 plots we recorded 3973 bee specimens, belonging to 91 species, 16 of which are red listed, revealing a high bee species richness in the study area. Wild bee species richness and abundance were best explained by habitat type, number of flowering plants and site. A strong relationship of increasing number of flowering plants and bee species richness and abundance was found. Grassland habitats, especially low-input meadows, harboured the highest species richness and abundances. Organic cereal fields showed a potential to conserve bee species relevant to nature conservation (harbouring exclusively two red list species and four rare species). Ordination analysis of the bee communities showed a relative dissimilarity between the habitat types and indicates their complementary effects to benefit the diversity of wild bees. Our results demonstrate that a matrix of low-input habitats are needed to sustain rich assemblages of wild bees in agroecosystems.

Maximizing pollinator diversity in willow biomass plantings: A comparison between willow sexes and among pedigrees

Shrub willow has potential to be a substantial source of renewable biomass for production of bioenergy, biofuels, and bioproducts. At the same time, scientists and land managers are increasingly challenged to achieve multiple ecosystem functions in bioenergy plantings. Due to willow's early-season bloom period, a time when natural forage for bees can be limited, biomass plantings offer a potential benefit of floral resources for pollinators, some of which are known to be experiencing recent declines. To assess which willow cultivars and sex may provide the most benefit to pollinators, we conducted a common-garden experiment (Northeast U.S.) comparing bee (Hymenoptera: Anthophila) visitation among seven pedigrees and both sexes of short rotation coppice willow. We quantified abundance, richness, diversity, evenness, and species composition in plots planted with each pedigree and sex. Over seven sampling dates, we found an abundant and diverse bee assemblage comprised of 4675 individuals representing >56 species, at least 10 of which are rare or in decline in the northeastern United States. Willow sex was an important factor in bee visitation differences, with male willows supporting 39% greater abundance, 20% greater richness, and 9% greater diversity of bee visitors. Greater bee richness and diversity on male willows was due to an abundance-driven accumulation of species, as determined via rarefaction. Ordination analyses indicated composition of bee species assemblages differed among both willow pedigree and sex. Thus, our findings suggest male willow of varying pedigrees may be optimal for strategic plantings intended to meet bioenergy goals while also benefiting pollinators.

Effects of fragments and landscape characteristics on the orchid bee richness (Apidae: Euglossini) in an urban matrix, southwestern Amazonia

Orchid bees are important pollinators in tropical forests. Although studies have already detected effects of habitat loss and forest fragmentation on bee assemblages, little is known about orchid bees in urban forest fragments. The aim of this study was to analyse the influence of forest fragments (size and edge index) and landscape features (forest cover area and built-up area around the forest fragments, connectivity and spatial distance from the urban center) on the abundance, richness and composition of orchid bees. Male bees were attracted by odoriferous baits and collected in ten forest fragments of different sizes. In total, we collected 3166 male bees belonging to 4 genera and 38 species. The increase of the built-up area and the reduction of the forest cover area around the forest fragments decreased the abundance and richness of bees. We recorded a smaller number of bees in areas closer to the urban center. We failed to find a significant relationship between abundance/richness of bees and forest fragment area, edge index, and connectivity. We observed that the faunistic dissimilarity was positively correlated with the geographic distance between forest fragments. The forest fragments that presented greater landscape dissimilarity also presented greater faunistic dissimilarity. Our results suggest that the matrix structure around the forest fragments is an important factor that influences the Euglossini bee assemblages inside these forest fragments. Based on our results, we believed that the conservation of fragments with a larger forest cover area and smaller built-up areas around them contribute to the maintenance of the diversity of orchid bees and their pollination services.