Bee Richness Research Articles

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.

Associations between plant and pollinator communities under grassland restoration respond mainly to landscape connectivity

Abstract Land‐use change can disrupt associations between different trophic groups, but it is unclear if habitat restoration can recover these associations. In Sweden, restoration efforts have been applied to increase areas of semi‐natural grassland previously remaining as small fragments due to abandonment. We assessed how the associations between plant and pollinator communities can be modified by grassland abandonment and restoration, together with landscape connectivity. We surveyed plant, hoverfly and bee communities in 10 abandoned, 18 restored and 10 intact grasslands in south‐central Sweden, distributed along a gradient of isolation from other species‐rich grasslands. We assessed the effects of management history and connectivity on the relationships between several measures of the composition of plant and pollinator communities as well as between plant community composition and pollinator guilds. The composition of the local flowering plant community was an important determinant of both hoverfly and bee communities. However, plant‐pollinator associations were modulated by landscape connectivity and, to some extent, by grassland management history. Abundance, species richness and functional richness of bees and species richness of hoverflies were positively associated with local plant communities in isolated grasslands, but these associations weakened in well‐connected grasslands. In contrast, hoverfly abundance correlated positively with plant communities in well‐connected grasslands. The response of pollinator feeding guilds was consistent with overall pollinator communities. However, abundance of bees adapted to foraging on particular plants (long‐tongued and short‐tongued) responded positively to specific host plant species abundance. Synthesis and applications. Our results show how land use and landscape context can significantly affect interactions between different trophic levels. Land use and landscape context should therefore be recognised in grassland restoration guidelines. Enhancement of both functional‐rich and species‐rich plant communities, as well as increasing abundance and species and functional richness of host plants for specialist pollinators will amend pollinator diversity. Restoration actions should consider the spatial configuration of the landscape to improve its outcome. Efforts in more isolated grasslands should focus on promoting local habitat quality while, in more connected grasslands, the priority should be maintaining connectivity to well‐preserved grasslands.

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.

Orchid Bees (Hymenoptera: Apidae: Euglossini) in Seasonally Dry Tropical Forest (Caatinga) in Brazil

Euglossini bees are important Neotropical pollinators, but there is a lack in the knowledge about this fauna in dry tropical environments. The aims of this study were to evaluate the richness and abundance of euglossine bees in two fragments of seasonally dry tropical forest (Caatinga), as well as to assess the distribution of euglossine species richness in the Caatinga environment. Males were collected along 12 consecutive months, using traps with aromatic baits. The species richness (S=5) was lower than in rainforests and savannas. Euglossa cordata (L.) was the dominant species in the assemblage, representing 70% of the individuals. The highest abundance occurred in the rainy season. Euglossini fauna presents low local species richness in Caatinga areas, however the beta diversity is higher, since assemblages in different habitats have differences in species composition.

Abelhas e espécies melitófilas da mata ciliar do riacho Salgadeira, município de Alcantil, Paraíba

A Caatinga encontra-se inserida no domínio intertropical e possui uma cobertura vegetal de formação xerofítica complexa. Sua degradação está contribuindo para o desaparecimento de espécies de plantas e animais. As abelhas, participam do processo de polinização, também se enquadram neste problema. Neste trabalho foram avaliadas a riqueza e abundância de abelhas em duas áreas de mata ciliar da Caatinga, nos trechos preservado e degrado (salinizado), do riacho Salgadeira. Nas áreas selecionadas foram coletadas abelhas e plantas no período de maio e junho de 2016. Cada amostra se caracterizou por doze coletas, em dois dias consecutivos entre 06h00min e 15h00minh. No levantamento realizado foram coletados 491 indivíduos de 34 espécies de abelhas, de cinco famílias. A composição da apifauna foi registrada por 52 indivíduos de 12 espécies exclusivas na parte da mata ciliar preservada, enquanto para a área degradada ocorreu, apenas, uma espécie, com 4 indivíduos. Apis mellifera e Trigona spinipes somaram 2/3 de todas as abelhas amostradas, principalmente da área degradada. Foi registrada a presença de Ceblurgus longipalpis, espécie oligolética, que mantém uma dependencia com Varronia leucocephala, sendo gênero Ceblurgus é o único endêmico da Caatinga. A partir dos resultados consideramos, que as abelhas de ambientes preservados estão ameaçadas, pela degradação com o desmatamento da cobertura vegetal na área.

Disappearing edge: the flowering period changes the distribution of insect pollinators in invasive goldenrod patches

Abstract The response of animals to the edge reveals the potential mechanism underlying the impact of invasive plants on native pollinators. Many invasive plants flower only during a part of the growing season, which creates a temporal pattern of the availability of resources. This can lead to the emergence or disappearance of the edge effect in the pollinator community in the patches dominated by alien plants. We tested whether the variability in the supply of flower resources created by dense stands of flowering invasive goldenrods could create a temporal edge effect for pollinating insects in a grassland landscape. We surveyed pollinator communities along transects perpendicular to the goldenrod‐grassland edge. To understand the variation in edge effects, we surveyed the number of flowers, which are the main food resources for pollinators. We found positive edge responses of abundance and species richness of all pollinator groups from the edges to the grassland interior before the goldenrod flowering period. During the goldenrod flowering period abundance and species richness of bees showed a neutral edge response, the response of butterflies and hoverflies towards the centre of the goldenrod patch were negative and positive respectively. Our results revealed that the emergence of the edge effect in a pollinating insect community is associated with temporal usability of invasive plants as a food source. Thus, the combined outcome of the available resources and invasion of alien plants can help to understand the edge effect on pollinator distributions in the invaded landscapes.

Recent post-wildfire salvage logging benefits local and landscape floral and bee communities

Understanding the implications of shifts in disturbance regimes for plants and pollinators is essential for successful land management. Wildfires are essential natural disturbances that are important drivers of forest biodiversity, and there is often pressure to respond to wildfire with management like post-wildfire logging (i.e., removal of dead trees for economic value immediately following wildfire). We investigated how local floral and bee density, species richness, and community composition and dispersion were influenced by post-wildfire logging, and how these effects differed between an older (24 years-since-fire) and a more recent (8 years-since-fire) wildfire in the Gallatin National Forest, Montana USA. We also tested how these local patterns scaled up to influence landscape patterns in floral and bee diversity. After recent wildfire, local floral and bee density and species richness were higher in logged than in unlogged sites, and these effects were variable over the course of the growing season. There were no differences in community dispersion except that of bees in logged areas of the recent wildfire, which were less heterogeneous compared to unlogged areas. Despite this reduction in bee community heterogeneity, overall bee diversity was highest across logged areas of the recent fire. While the positive effects of post-wildfire logging on local density and richness did not persist in the older fire, compositional differences in flowers and bees between logged and unlogged areas were observed in both the recent and older wildfire. Together, these results suggest that the local benefits of post-wildfire logging for floral and bee richness are evident within a decade of these disturbances, but have diminished within a quarter century of fire. Nevertheless, compositional effects persist, resulting in higher overall landscape floral and bee diversity when both logged and unlogged areas of each wildfire were present. This study provides evidence for near-term benefits of post-wildfire logging for local and landscape floral and bee communities. Post-wildfire logging may be considered as a forest management option when balanced with the maintenance of unlogged areas to encourage biodiversity conservation at the landscape scale.

City parks vs. natural areas - is it possible to preserve a natural level of bee richness and abundance in a city park?

Urbanisation is an expansive process and a majority of insects live in human-modified areas. At the same time, a decrease in pollinator species richness and abundance has recently been observed in Europe, which in turn may have serious ecological and economic consequences. This study investigates the abundance, species richness and functional traits of wild bees in urban city parks in comparison to natural areas. The aim of this research was to assess the potential conservation values of urban green areas for bees. The present study demonstrates that a large and diversified city park may be a favourable habitat for bees, comparable to the natural fauna both in terms of the number and abundance of bee species. However, the study also showed that there were differences in the occurrence of species with different functional traits in the city parks investigated and in the natural landscape.

Bee diversity in crop fields is influenced by remotely-sensed nesting resources in surrounding permanent grasslands

Landscape heterogeneity is an important driver of biodiversity in agroecosystems. However, the functional heterogeneity of agricultural landscapes, taking into account the different resources that habitat patches can provide to species, has rarely been studied. In this study, we explored the effect of landscape-scale nest availability provided by permanent grasslands on wild bee communities. Wild bees were sampled in 43 cereal fields in south-western France differing in the surrounding proportion of permanent grasslands. Using remote sensing tools, we measured two parameters of grassland structure known to locally influence bee nest density (slope and proportion of sparse vegetation). We found that mean slope of surrounding grasslands was the factor that most positively influenced bee richness, abundance and trait distribution in bee communities. We also found that mean slope of surrounding grasslands had a better predictive power of bee community structure than the proportion of permanent grasslands. Ground-nesting species, species with high dispersal capacities and species with a generalist diet were positively affected by the availability of sloped ground in the surrounding permanent grasslands. Only bee species with specialized flower requirements responded positively to the proportion of sparse vegetation in grasslands. Our results suggest that landscape-scale availability of nesting resources provided by grasslands affects bee communities in agricultural landscapes and can help sustain functionally diverse bee assemblages. Using simple remote sensing tools, this study highlights the importance of considering nesting resources in agricultural landscapes to maintain wild bee diversity in farmlands.

Restore it, and they will come: trap-nesting bee and wasp communities (Hymenoptera: Aculeata) are recovered by restoration of riparian forests

Riparian forests have been greatly affected by anthropogenic actions with formerly continuous riparian forests being slowly converted into small and isolated patches. Riparian forests are extremely important habitats for many groups of insects, including bees and wasps, because they are sources of shelter and food for them and their offspring. There is a growing body of evidence of success in the restoration of riparian forest plant communities; however, little research has been done on the associated invertebrate communities. We test whether restoring plant communities is sufficient for restoring the taxonomic composition of trap-nesting bees and wasps and which functional traits are favored in different sites. We predict that species richness, abundance, and community composition of trap-nesting bees and wasps of riparian sites undergoing restoration will converge on the “target” of a reference site with increasing time, since restoration increases habitat complexity. We also predict that the width of restored patches will also influence the species richness, abundance and community composition of trap-nesting bees and wasps. Bee richness and abundance, and wasp richness, were strongly related to fragment width, but not to age since restoration. Our results indicate that although restored sites are relatively small and scattered in a fragmented landscape, they provide suitable habitat for re-colonization by community assemblages of trap-nesting bees and wasps and the traits selected captured the responses to the habitat restoration. Hence, restored riparian areas can be considered important habitats for invertebrates, thus contributing to an increase in local biodiversity and, possibly, the restoration of some of the ecosystem services they originally provided.

To mow or to mow less: Lawn mowing frequency affects bee abundance and diversity in suburban yards

Green spaces embedded within the urban matrix, particularly residential yards, could mitigate negative aspects of urban development and provide pollinator habitat. Lawns represent a dominant green space, and their management consists of frequent mowing to inhibit the growth of ostensibly “weedy” species (e.g., dandelions and clover). Since widespread population declines of bees and other pollinators from habitat loss are a growing concern, these spontaneous flowers could provide pollen and nectar sources throughout the growing season. We experimentally tested whether different lawn mowing frequencies (1, 2 or 3 weeks) influenced bee abundance and diversity in 16 suburban western Massachusetts yards by increasing lawn floral resources. Lawns mowed every three weeks had as much as 2.5 times more lawn flowers than the other frequencies. Interestingly, lawns mowed every two weeks supported the highest bee abundance yet the lowest bee richness and evenness. We suggest these patterns were driven by a combination of more abundant floral resources (compared with 1-week yards), easier access to lawn flowers due to shorter grass and a more drastic impact on grass biomass and floral resources (compared with 3-week yards), and the dominance of a few generalist bees overwhelming our samples, thus driving richness and evenness. Our results highlight a “lazy lawnmower” approach to providing bee habitat. Mowing less frequently is practical, economical, and a timesaving alternative to lawn replacement or even planting pollinator gardens. Given the pervasiveness of lawns coupled with habitat loss, our findings provide immediate solutions for individual households to contribute to urban conservation.

Forest-edge associated bees benefit from the proportion of tropical forest regardless of its edge length

Natural areas are important for wild bees in human-dominated landscapes as they provide permanent feeding and nesting resources. Understanding how bee communities vary with the amount of natural areas is thus key to guide conservation measures. This information, however, is largely lacking in montane tropical ecosystems. Here we explore to what extent the amount of forest area or forest edge (as landscape variables) influence the species richness and abundance of forest-edge associated bees in the Colombian Andes. In addition, we assess the effects of flower species richness and abundance (as local variables) to better understand the individual and interactive effects of forest conservation. Bees were surveyed along 20 forest edges differing in forest proportion and forest edge length within four spatial scales (250, 500, 1000 and 1500 m radii). We conducted trait-specific analyses as bees with different traits associated to body size, sociality and nesting behavior might differ in their response to local and landscape variables. We found that overall bee species richness and abundance increased with an increasing proportion of forest within 1000 m radius, but also with flower abundance. Similarly, the species richness and abundance of social, large and above-ground nesting bees increased with an increasing proportion of forest area, mainly within 500 and 1000 m radii. However, only the abundance (not the species richness) of solitary and small bees were positively related to the proportion of forest within 1000 m. Below-ground nesters did not respond to the individual effect of forest area at any spatial scale. Interactive effects between local and landscape variables were mainly found between flower richness and the proportion of forest. Forest edge length influenced only the abundance of solitary bees. These findings highlight the importance of conserving and/or restoring forest areas – at meaningful spatial scales – to promote diverse bee communities in montane tropical regions.

Small-scale agricultural landscapes and organic management support wild bee communities of cereal field boundaries

Pollinators are sensitive to agricultural intensification at both local and landscape scales. High configurational landscape heterogeneity due to small fields and a high amount of field boundaries is hypothesized to enhance farmland biodiversity. Here, we investigated the effects of organic vs. conventional farming in large- vs. small-scale agricultural landscapes on wild bee communities and their floral resources to improve conservation schemes for pollinators. We sampled bees in Central Germany at the field boundaries of 18 pairs of conventionally and organically managed winter wheat fields along the former iron curtain using pan traps and trap nests. Around traps, we surveyed species richness and flower cover of insect-pollinated forbs. Compared to conventional farming, organic farming was related to higher insect-pollinated forb species richness and flower cover in the field boundaries, presumably due to the lack of herbicide use. Interestingly, small-scale agriculture did not counteract the loss of floral resources under conventional management, as the difference to organic management was even larger in Western small-scale agriculture. Organic farming, but not small-scale agriculture, enhanced species richness of solitary bees, which is in line with their small home ranges. In contrast, bumblebees benefitted only from small-scale agriculture, which matches with their high dispersal ability. Despite similar levels of abundance and diversity of trap-nesting bees in the two landscape types, brood cell parasitism was also higher in small-scale agriculture. Both organic farming and small-scale agriculture directly and indirectly supported different groups of wild bees, suggesting long-term benefits for conservation. Agri-environment schemes should acknowledge the so far neglected benefits of small-scale agriculture for biodiversity and its potential services.

Selecting cost-effective plant mixes to support pollinators

Growing concern about wild and managed pollinator populations has led to efforts to create floral habitat to promote bees and other pollinators, especially in agricultural lands where they make important contributions to crop pollination. These actions all require practitioners to determine what mixture of plant species to select to best support diverse and functionally important pollinators. Like in the selection of areas for nature reserves, plant choices must balance function against differences in cost. To date, plant mixes have been compiled using expert opinion based on the performance of individual species, but researchers and practitioners have called for a systematic approach to optimize mixtures. We applied a decision analytic approach to select best flowering mixes to meet two specified objectives at the least cost: maximizing total bee richness or maximizing crop-pollinating bees. The model identified best plant mixes for each objective across a range of budgets. Accounting for the variation in costs among plant species allowed for substantially more cost effective mixes with little loss in achieving the target objective. Including multiple objectives simultaneously revealed the power of the approach to meet complex goals. The resulting mix supported over 96% of the bee species for both goals at no difference in cost. This gain in efficiency could dramatically increase the extent of habitat implemented and remove financial barriers to adoption by stakeholders and conservation practitioners.

Wild bee and floral diversity co‐vary in response to the direct and indirect impacts of land use

AbstractLoss of habitat area and diversity poses a threat to communities of wild pollinators and flowering plants in agricultural landscapes. Pollinators, such as wild bees, and insect‐pollinated plants are two groups of organisms that closely interact. Nevertheless, it is still not clear how species richness and functional diversity, in terms of pollination‐relevant traits, of these two groups influence each other and how they respond to land use change. In the present study, we used data from 24 agricultural landscapes in seven European countries to investigate the effect of landscape composition and habitat richness on species richness and functional diversity of wild bees and insect‐pollinated plants. We characterized the relationships between the diversity of bees and flowering plants and identified indirect effects of landscape on bees and plants mediated by these relationships. We found that increasing cover of arable land negatively affected flowering plant species richness, while increasing habitat richness positively affected the species richness and functional diversity of bees. In contrast, the functional diversity of insect‐pollinated plants (when corrected for species richness) was unaffected by landscape composition, and habitat richness showed little relation to bee functional diversity. We additionally found that bee species richness positively affected plant species richness and that bee functional diversity was positively affected by both species richness and functional diversity of plants. The relationships between flowering plant and bee diversity were modulated by indirect effects of landscape characteristics on the biotic communities. In conclusion, our findings demonstrate that landscape properties affect plant and bee communities in both direct and indirect ways. The interconnection between the diversities of wild bees and insect‐pollinated plants increases the risk for parallel declines, extinctions, and functional depletion. Our study highlights the necessity of considering the interplay between interacting species groups when assessing the response of entire communities to land use changes.

Habitat restoration benefits wild bees: A meta‐analysis

Abstract Pollinator conservation is of increasing interest in the light of managed honeybee (Apis mellifera) declines, and declines in some species of wild bees. Much work has gone into understanding the effects of habitat enhancements in agricultural systems on wild bee abundance, richness and pollination services. However, the effects of ecological restoration targeting “natural” ecological endpoints (e.g. restoring former agricultural fields to historic vegetation types or improving degraded natural lands) on wild bees have received relatively little attention, despite their potential importance for countering habitat loss. We conducted a meta‐analysis to evaluate the effects of ecological restoration on wild bee abundance and richness, focusing on unmanaged bee communities in lands restored and managed to increase habitat availability and quality. Specifically, we assessed bee abundance and/or richness across studies comparing restored vs. unrestored treatments and studies investigating effects of specific habitat restoration techniques, such as burning, grazing, invasive plant removal and seeding. We analysed 28 studies that met our selection criteria: these represented 11 habitat types and 7 restoration techniques. Nearly all restorations associated with these studies were performed without explicit consideration of habitat needs for bees or other pollinators. The majority of restorations targeted plant community goals, which could potentially have ancillary benefits for bees. Restoration had overall positive effects on wild bee abundance and richness across multiple habitat types. Specific restoration actions, tested independently, also tended to have positive effects on wild bee richness and abundance. Synthesis and applications. We found strong evidence that ecological restoration advances wild bee conservation. This is important given that habitat loss is recognized as a leading factor in pollinator decline. Pollinator responses to land management are rarely evaluated in non‐agricultural settings and so support for wild bees may be an underappreciated benefit of botanically focused management. Future restoration projects that explicitly consider the needs of wild bees could be more effective at providing nesting, foraging and other habitat resources. We encourage land managers to design and evaluate restoration projects with the habitat needs of wild bee species in mind.

Key environmental determinants of global and regional richness and endemism patterns for a wild bee subfamily

Reports of world-wide decline of pollinators, and of bees in particular, raise increasing concerns about maintenance of pollination interactions. While local factors of bee decline are relatively well known and potential mitigation strategies at the landscape scale have been outlined, the regional and continental-scale threats to bee diversity have only been marginally explored. Here we document large-scale spatial patterns for a representative bee subfamily, the determinants of its species richness, and assess major threats to these pollinators. Using a comprehensive global dataset of Colletinae (genera Colletes, also called “polyester” or “cellophane” bees for their underground nests lined with a polyester secretion, and Mourecotelles), a species-rich subfamily whose organismal and physiological ecology is representative of many bees, we measured species richness and endemism on global to continental scales. We explored the relationships between bee species richness and potential environmental stress factors grouped into three categories: contemporary climate, habitat heterogeneity, and anthropogenic pressure. Bees of the subfamily Colletinae demonstrate the reversed latitudinal gradient in species richness and endemism suggested for bees; the highest species richness of Colletinae was found between 30° and 50° latitude in both the northern and southern hemispheres. Centres of endemism largely overlapped with those of species richness. The importance of the Greater Cape Floristic Region, previously identified as a centre of richness and endemism of bees, was confirmed for Colletinae. On the global scale, present-day climate was a significant predictor of species richness as was flowering plant diversity represented by vascular plant species richness and centres of plant diversity. Our main conclusion is that climate change constitutes a potential threat to bee diversity, as does declining diversity of vascular plants. However, a significant overlap between centres of bee richness and plant diversity might increase chances for developing conservation strategies.

Coupling of pollination services and coffee suitability under climate change

Climate change will cause geographic range shifts for pollinators and major crops, with global implications for food security and rural livelihoods. However, little is known about the potential for coupled impacts of climate change on pollinators and crops. Coffee production exemplifies this issue, because large losses in areas suitable for coffee production have been projected due to climate change and because coffee production is dependent on bee pollination. We modeled the potential distributions of coffee and coffee pollinators under current and future climates in Latin America to understand whether future coffee-suitable areas will also be suitable for pollinators. Our results suggest that coffee-suitable areas will be reduced 73-88% by 2050 across warming scenarios, a decline 46-76% greater than estimated by global assessments. Mean bee richness will decline 8-18% within future coffee-suitable areas, but all are predicted to contain at least 5 bee species, and 46-59% of future coffee-suitable areas will contain 10 or more species. In our models, coffee suitability and bee richness each increase (i.e., positive coupling) in 10-22% of future coffee-suitable areas. Diminished coffee suitability and bee richness (i.e., negative coupling), however, occur in 34-51% of other areas. Finally, in 31-33% of the future coffee distribution areas, bee richness decreases and coffee suitability increases. Assessing coupled effects of climate change on crop suitability and pollination can help target appropriate management practices, including forest conservation, shade adjustment, crop rotation, or status quo, in different regions.

Exploring the relationships between landscape complexity, wild bee species richness and reproduction, and pollination services along a complexity gradient in the Netherlands

Pollinator communities exhibit variable responses to changing landscape composition. A general expectation is that a decreasing cover of semi-natural habitats negatively affects pollinator reproduction, population size and pollination services, but few studies have investigated the simultaneous effects of landscape complexity on different aspects of pollinator communities and functioning.In 20 agricultural landscape plots the size of an average Dutch farm, we studied how changing landscape complexity affected wild bee abundance, species richness and reproduction. To measure pollination, we placed potted strawberry plants as phytometers in landscapes. Landscape complexity was characterized as the area of semi-natural habitats. In addition, we estimated floral resource abundance in each landscape plot. We expected that i) bee species richness, reproduction and pollination would be positively related to area of semi-natural habitats and flower abundance, and that ii) species richness and reproduction would be positively related to pollination.An increase in semi-natural habitats in landscapes increased both the abundance of cavity-nesting bees colonizing trap nests, and the growth rates of experimental Bombus terrestris L. colonies, but not the species richness of wild bees measured by pan traps. There was only a tendency for higher pollination levels of strawberry plants with higher cover of semi-natural habitats. There was no relationship between species richness and bee reproduction in a landscape and the pollination services. Estimated flower abundance in landscape had a positive effect on bumblebee colony growth only and not on the other variables.Our results suggest that, by improving habitat quality on their farms through establishing more semi-natural habitats or enhancing the flower availability in semi-natural habitats, farmers can promote reproduction of a number of functionally important bee species and the pollination services they provide. Bee species richness, however, seems to be more difficult to enhance and requires more than just creating more of the same type of habitats or flowers.

Comparison of Orchid Bee (Hymenoptera: Apidae) Species Composition Collected with Four Chemical Attractants

Abstract Orchid bees (Hymenoptera: Apidae: Euglossini) are a diverse and important group of Neotropical pollinators. Numerous chemicals have been used in sampling orchid bees, and species-specific attraction, particularly of males, to these chemicals is well known. However, there have been few studies that have quantified differences in the species composition of orchid bees attracted to particular chemicals. In this study, we compared the abundance and species composition of orchid bees collected with 4 commonly used attractants: benzyl acetate, eucalyptol (or cineole), eugenol, and methyl salicylate. Eucalyptol collected the greatest abundance and species richness of orchid bees. Indicator species analysis revealed that 3 species, Euglossa imperialis Cockerell, Euglossa obtusa Dressler, and Eufriesea mexicana (Mocsary), were significantly associated with eucalyptol, and 1, Eulaema marcii Nemesio, with benzyl acetate. The multi-response permutation procedure revealed relatively large differences in speci...