Bee Richness Research Articles

Coastal habitats across sea-to-inland gradient sustain endangered coastal plants and Hymenoptera in coastal dune ecosystems of Japan

Coastal sand dune ecosystems have been lost and increasingly fragmented due to human use and disaster prevention over the past few decades. Generally, habitat fragmentation and connectivity loss have led to the decline of species biodiversity. In coastal dune ecosystems, habitat loss across the coastal gradient may be a major driver of the decline in coastal species diversity and ecosystem functions. In this study, we assessed the species richness of coastal plants and hymenopteran insects in fragmented coastal dunes of Japan using six sites with and without back-dune habitats. We recorded plant species and their flowering status monthly from April to September 2018 and examined the effects of landscape factors on plant species richness. We also assessed the species richness of hymenopteran bees and wasps and compared their determinants with those of plants. In total, we identified 109 plant species, including 33 native coastal plants (10 of which are endangered) and 40 exotic plants. The number of native plant species was positively affected by the presence of back-dune habitat and sand dune size, while that of native coastal plant species was positively affected only by the presence of back-dune habitat. In contrast, the number of exotic plant species was dependent only on sand dune size. We recorded 58 hymenopteran species including 28 bee pollinators and 30 predatory wasp species. The number of hymenopteran species was positively related to the number of native plant species for both bees and wasps. In conclusion, habitat loss across the coastal gradients led to decreased species richness of native coastal plant species, resulting in reduced species richness of pollinator and predatory insect communities. Most of the coastal areas across sea-to-inland gradients have been lost due to recent disaster prevention activities. Our results highlight the urgent need for biodiversity conservation of endangered species in remnant coastal dune ecosystems.

Conservation in post‐industrial cities: How does vacant land management and landscape configuration influence urban bees?

Abstract Rich pollinator assemblages are documented in some cities despite habitat fragmentation and degradation, suggesting that urban areas have potential as pollinator refuges. To inform urban bee conservation, we assessed local‐ and landscape‐scale drivers of bee community composition and foraging within vacant lots of Cleveland, Ohio, USA. Cleveland is a shrinking city, a type of urban area that has an over‐abundance of vacated greenspaces as a result of population loss and subsequent demolition of abandoned infrastructure. As such, Cleveland represents over 350 post‐industrial cities worldwide that are all promising locations for bee conservation. Across a network of 56 residential vacant lots (each ~30 m × 12 m), we established seven unique habitats, including seeded native prairies, to investigate how vegetation management and landscape context at a 1,500 m radius influenced urban bee communities. We assessed the distribution of several bee functional traits, diversity and abundance with pan and malaise traps. Foraging frequency was determined with plant–pollinator interaction networks derived from vacuum collections of bees at flowers. We observed higher bee richness and increased abundance of smaller sized bees as the size of surrounding greenspace patches increased within a 1,500 m radius landscape buffer. Within habitats, seeded treatments had no effect on bees but greater plant biomass and shorter vegetation were correlated with increased bee richness and abundance. Plant–pollinator interaction networks were dominated by spontaneous non‐native vegetation, illustrating that this forage supports urban bees. Synthesis and applications. Our study indicates that proximity to larger greenspaces within an urban landscape promotes overall bee richness and increased occurrence of smaller bee species within residential vacant lots. While we did not observe our seeded native plants enhancing the bee community, native wildflowers were still establishing during the study and may have a greater influence when blooming at higher densities. Importantly, spontaneous non‐native vegetation provided the majority of urban bee's forage. Thus, vacant land that is minimally managed and vegetated with what many consider undesirable ‘weeds’ provides valuable habitat for bee conservation in cities.

Bee abundance and soil nitrogen availability interactively modulate apple quality and quantity in intensive agricultural landscapes of China

Bees provide important pollination services for crops, but pollination limitation is a common problem in agricultural landscapes worldwide. To promote ecological intensification in fruit production, more knowledge is needed concerning the interacting effects of insect pollination services and soil fertility on crop quality and quantity. We investigated the effects of three pollination treatments (open, self and hand pollination) on apple quantity and quality parameters. We also analyzed the effects of bee abundance (wild bees and managed honeybees (Apis mellifera)) and soil nitrogen on fruit quantity and quality, and the responses of bee abundance and species richness to landscape metrics. Apple fruit set and yield of open pollinated flowers increased by 57 % and 25 t/ha (compared to bagged controls), respectively. Hand pollination further enhanced yields by 7 t/ha (compared to open pollination; i.e. to 39 t/ha), indicating pollination limitation in the orchards. Seed number was highest in open pollinated fruits, and increased with bee abundance if soil nitrogen was low, but decreased with bee abundance at high nitrogen levels, possibly due to higher flower density resulting in pollinator dilution effects. Higher seed numbers reduced the proportion of deformed apples and thus increased fruit quality. The percent of surrounding semi-natural habitats positively affected species richness of wild bees in apple orchards. We conclude that yield and quality of apples may benefit from ecological intensification comprising the augmentation of wild bees by semi-natural habitat and lowering of fertilizer inputs.

Forest Matrix Fosters High Similarity in Bee Composition Occurring on Isolated Outcrops Within Amazon Biome.

Most studies analyze fragmentation due to habitat loss caused by anthropogenic activities and few of them analyzed fragmentation on naturally fragmented areas. In the Eastern Amazon, it is possible to find areas naturally open and surrounded by pristine forest. Understanding how species respond to isolation in these areas is an important challenge for decision-making processes aiming conservation and restoration. Using standardized methods of bee collection (entomological nets, bait trap, pan trap, and nest trap), the objective of this study was to analyze the composition and diversity of bees occurring on six isolated outcrops located in two protected areas within Amazon biome. More specifically, we tested 1) if the dissimilarity in bee species composition is explained by the isolation of outcrops and 2) if bee richness, abundance, and Shannon diversity can be explained by the outcrop size. We found 118 species, with the Meliponini and Euglossini (Hymenoptera: Apidae) tribes representing the highest number of species. The similarity in species composition across all outcrops is high and is not explained by the isolation. In addition, the richness, abundance, and Shannon diversity are not explained by outcrop size. Forest does not seem to be a barrier to bee movement, and although most species probably nest in the forests, they use the highly diverse plants of the outcrops as a complementary food source.

No Mow May lawns have higher pollinator richness and abundances: An engaged community provides floral resources for pollinators.

No Mow May is a community science initiative popularized in recent years that encourages property owners to limit their lawn mowing practices during the month of May. The goal of No Mow May is to provide early season foraging resources for pollinators that emerge in the spring, especially in urban landscapes when few floral resources are available. We worked with the city council of Appleton, Wisconsin, USA. to allow No Mow May to take place in May 2020. Four hundred and thirty-five property owners registered for No Mow May in Appleton. We measured floral and bee richness and abundance in the yards of a subset of homes (N = 20) located near regularly mowed urban parks (N = 15) at the end of the month. We found that homes that participated in No Mow May had more diverse and abundant flora than regularly mowed green spaces throughout the city. No Mow May homes had three times higher bee richness and five times higher bee abundances than frequently mowed greenspaces. Using generalized linear models, we found that the best predictor of bee richness was the size of the designated unmowed area, and the best predictors of bee abundances were the size of the unmowed area as well as floral richness. While our findings cannot conclusively attribute increases in bee abundances and richness to the No Mow May efforts, our data does show that bee pollinators make use of no mow spaces as key floral resources during early spring in the upper midwestern United States. A post-No Mow May survey revealed that the participants were keen to increase native floral resources in their yards, increase native bee nesting habitat, reduce mowing intensities, and limit herbicide, pesticide, and fertilizer applications to their lawns. The No Mow May initiative educated an engaged community on best practices to improve the conservation of urban pollinators in future years.

Functional groups of wild bees respond differently to faba bean Vicia faba L. cultivation at landscape scale

Abstract Concerns about insect declines are growing and the provisioning of ecosystem services like pollination may be threatened. To safeguard biodiversity, greening measures were introduced within the reform of the EU's Common Agricultural Policy. One measure commonly applied by farmers is the cultivation of nitrogen fixing crops. Although underlying studies are largely missing, this measure is criticized as providing no significant biodiversity benefit. Using a landscape‐scale approach, we selected 30 paired study landscapes (1 km × 1 km) in Germany, that is, 15 study landscapes with faba bean (FB) fields (Vicia faba L.) and 15 without any grain legumes. Flower‐visiting wild bees were recorded with transect walks at the field margins of different crops using a stratified sampling approach. We analysed the effect of FB cultivation and landscape composition on the abundance and species richness of wild bees as well as on the functional composition of the bee communities. Bumblebee densities (Bombus spp. Latreille) were more than twice as high in FB compared to control landscapes after the flowering of the beans. Non‐Bombus wild bee densities, however, were not affected by FB cultivation, but were enhanced by increasing amounts of semi‐natural habitats (SNH). After the beans' blooming had ceased, FB landscapes had a higher proportion of wild bees collecting pollen from Fabaceae than control landscapes. The community‐weighted means for bee size, measured as intertegular distance, were not affected by FB cultivation, but we found smaller species and species with shorter tongues with an increasing percentage of SNH. Synthesis and applications. The cultivation of faba bean Vicia faba L. strongly increased bumblebee densities throughout the season. This indicates that also on‐field greening measures can support biodiversity. Nevertheless, since only functional groups adapted to faba bean benefit, measures to promote semi‐natural habitats in agricultural landscapes need to be implemented. We conclude that the combination of on‐ and off‐field measures is essential to maintain farmland biodiversity and the Common Agricultural Policy should furthermore promote both.

Rapid recovery of plant–pollinator interactions on a chronosequence of grassland-reclaimed mines

Reclamation of abandoned mines to grassland may benefit non-target wildlife like pollinators by providing conservation habitat. Co-colonization of wildflowers and pollinators has been used to measure ecological recovery in other disturbed herbaceous habitats. Revegetated surface coal mines in eastern North America are a unique system in which to study re-establishment of plant–pollinator interactions because they are field islands isolated by forest. Using a time series of 10 grassland-reclaimed mines (aged 20 years) in Ohio, USA, we evaluate whether former mines provide habitat for bees, seek insights into species accumulation as sites mature, and examine the consequences for bee conservation and plant–pollinator interactions. In 120 h of netting over two consecutive years, we documented 7749 bees of 139 species visiting 117 wildflower species. Bee richness did not differ between young and mature sites, suggesting that diverse communities established rapidly following reclamation and persisted. Bee species assemblage, however, differed between sites 10 years post-reclamation, and was influenced by vegetation and the amount of nearby forest. Plant–bee networks on sites > 10 years old had more links per species and greater network nestedness than new reclamations, suggesting the development of a core community of interacting species that stabilize pollination services over time. Reclamation grasslands are not typically considered high-quality pollinator conservation habitat, but we found that they harbor a diverse bee fauna similar to other regional meadow habitats. Reclaimed mines remain undeveloped for many years, and can accumulate pollinator species and export bees to the surrounding landscape.

Urban fragment of the Atlantic Rainforest as a refuge for cavity-nesting bees and wasps (Hymenoptera: Aculeata)

ABSTRACT Due to the fragmentation of many natural habitats, urban areas have become important refuges for various species, including bees and wasps. The present study aimed to determine the species composition, richness, and abundance of solitary bees and wasps that nest in pre-existing cavities in an urban fragment of the Atlantic Rainforest in the city of Salvador, Brazil. Data on the occupancy of the trap-nests and offspring mortality are also reported. The study was conducted at the Parque Zoobotânico Getulio Vargas (PZBGV) and the campus of Universidade Federal da Bahia (UFBA), the areas of which form the urban fragment. Traps were inspected once a month for 2 years. The composition and diversity of bee species were similar between the areas, but richness and abundance of wasp species were higher at UFBA. Centris analis (Fabricius) was the most abundant bee species in both areas, and Podium denticulatum (Smith) and Trypoxylon sp.2 were the most abundant wasp species at UFBA and PZBGV, respectively. Most nesting of these species occurred in the warm season. Centris analis and Trypoxylon sp.2 preferred traps made of cardboard, whereas P. denticulatum was the most generalist species, occupying all types of trap-nests. The main factor of mortality among immature specimens was ‘unknown cause’ for both bees and wasps. Only three species of natural enemies emerged from nests of C. analis. The increase in the richness of bee and wasp species in comparison with the results showed in previous studies made in the same areas indicates that the fragment offers valuable nesting places for species of cavity-nesting bees and wasps and can ensure the maintenance of these insects.

Forest proximity rather than local forest cover affects bee diversity and coffee pollination services

As agricultural demands for land continues to expand, strategies are urgently needed to balance agricultural production with biodiversity conservation and ecosystem service provision in agricultural landscapes. We used a factorial landscape design to assess the relative contributions of forest proximity and local forest cover to bee diversity and the provision of coffee pollination services. We quantified bee diversity and fruit set in 24 sun-grown coffee fields in Southeast Region of Brazil that were selected following a factorial sampling design to test the independent effects of local forest cover (in a radius of 400 m) and proximity to forest fragments. To assess the impact of landscape simplification, we also evaluated local coffee cover. Bee richness and abundance were higher in the proximity of forest fragments, but only bee abundance decreased when the coffee cover dominated the surrounding landscapes. Coffee fruit set was 16% higher overall with bee visitations compared with bee exclusion and increased to 20% when coffee bushes were near forest fragments, and the coffee cover was low. Surprisingly, local forest cover did not affect the bee community or coffee fruit set. Our results provide clear evidence that the proximity of coffee crops to forest fragments can affect the abundance and richness of bees visiting the coffee flowers and thereby facilitate the provision of pollination services. The positive association between forest proximity and fruit set reinforces the importance of natural vegetation in enhancing bee diversity and, therefore, in the provision of pollination services. The negative effect of coffee cover on fruit set at the local scale suggests that the service demand can surpass the capacity of pollinators to provide it. These effects were independent of the local forest cover, although all studied landscapes had more than 20% remaining forest cover (within a 2 km radius), which is considered the extinction threshold for Atlantic Forest species. Interspersion of forest fragments and coffee plantations in regions with more than 20% of forest cover left could thus be a useful landscape management target for facilitating pollinator flows to coffee crops and thus for increasing coffee yields.

Wild bee (Apiformes) communities in contrasting habitats within agricultural and wooded landscapes: implications for conservation management

Abstract Semi‐natural habitats are characterized by a high diversity of wildlife. However, other areas, e.g. old fields, can also play an important role in biodiversity conservation. We assessed the species richness, abundance, and diversity of wild bees (Apiformes), including species of various functional groups in two contrasting and differently managed landscape types. For this study, we selected 15 xerothermic or sandy grasslands or extensively managed fresh meadows located in agricultural landscapes as well as 15 old fields located in wooded landscapes. The study sites differed in area, stage of succession, and management regime. We did not detect any significant differences in total species richness, abundance, and diversity of Apiformes between the two landscape types, which suggests that both semi‐natural habitats and old fields are highly attractive to bees. The two habitat types, however, differed in species composition and proportions of functional groups. We found that in wooded landscapes, eusocial, hive‐nesting, and large‐sized species increased in abundance. The collected information on the preferences of Apiformes in respect of various habitats and landscapes makes it possible to protect and restore valuable habitats through the implementation of suitable methods of management, both locally and on the scale of landscapes.

Temperate agroforestry systems provide greater pollination service than monoculture

Insect pollination is a globally important ecosystem service, contributing to crop yields, production stability and the maintenance of wild plant populations. Ironically, agriculture is one of the major global drivers of wild insect pollinator decline. At the same time, increasing human population is driving ever greater demands on crop production. Agroforestry (AF) – a more diverse farming system integrating woody and agricultural crops – can theoretically reconcile high production with provision of ecosystem services such as pollination. However, empirical studies of pollination in temperate AF systems are almost entirely lacking. We sought to fill this knowledge gap by assessing whether AF can provide increased pollination service compared to monoculture (MC) systems. Six UK sites, each containing an AF and a MC system, were studied over three years. Wild pollinator abundance and diversity were used as proxies for the magnitude and stability, respectively, of the pollinating community. We also directly measured pollination service as seed set in a wild plant phytometer. We found that temperate AF systems can provide greater pollination service than MC: AF treatments had twice as many solitary bees and hoverflies, and in arable systems 2.4 times more bumblebees, than MC treatments. AF also had 4.5 times more seed set compared to MC in one of the two years. At 40% of site-by-year sampling units, species richness of solitary bees was on average 10.5 times higher in AF treatments. This provides evidence in favour of the expectation that AF systems can support higher pollinator richness, and therefore greater potential stability, of pollination service. For the other sampling units, and for bumblebees (Bombus spp.), there was no treatment effect on species richness. Further work is needed to investigate the effect of AF on species richness and its mechanistic basis. Our results also highlight the importance of AF system design, ensuring that ecosystem services outcomes are explicitly planned at the design stage. We suggest that AF has a role to play in improving the sustainability of modern farming and in mitigating the ongoing loss of wild pollinating insects, which is strongly driven by prevailing agricultural practices.

The relative importance of green infrastructure as refuge habitat for pollinators increases with local land‐use intensity

Abstract Agricultural expansion and intensification have resulted in strong declines in farmland biodiversity across Europe. In many intensively farmed landscapes, linear landscape elements such as field boundaries, road verges and ditch banks are the main remaining green infrastructures providing refuge for biodiversity, and as such play a pivotal role in agri‐environmental policies aiming at mitigating biodiversity loss. Yet, while we have a fairly good understanding of how agricultural intensification influences biodiversity on farmland, little is known about whether and how local land‐use intensity affects biodiversity in nearby linear landscape elements and how this affects their role as biodiversity refuge. Focussing on pollinating insects, we examined the effects of local land‐use intensity on biodiversity in agricultural fields and adjacent green infrastructures. In an intensively farmed area in south‐western France, we selected 23 agricultural grasslands and nearby field boundaries along a gradient in grassland cutting frequency which acted as a proxy for land‐use intensity. We analysed how grassland cutting frequency affects species richness, abundance and community composition of wild bees and hoverflies in the grasslands and neighbouring field boundaries, and whether these effects differ across habitat types and species groups. Grassland cutting frequency negatively affected pollinator species richness and abundance in the grasslands, whereas pollinators in the neighbouring field boundaries were unaffected. These responses reflected the effects of cutting frequency on floral resources, with flower cover and richness decreasing in grasslands but not in field boundaries. As a result, the proportion of the local pollinator community supported by field boundaries increased with the increasing cutting frequency of the adjacent grassland. Common and rare pollinator species generally showed similar responses. Furthermore, communities of plants and pollinators in field boundaries next to intensively farmed grasslands were fairly similar to those next to extensively farmed ones. Synthesis and applications. Our results suggest that, as nearby land use intensifies, flower‐rich field boundaries become increasingly important as pollinator refuge habitats. Conserving field boundaries and other green infrastructures, and maintaining or enhancing their quality, therefore constitute important tools to conserve and promote pollinators in intensively farmed landscapes.

Floral resources of an invasive shrub alter native bee communities at different vertical strata in forest-edge habitat

Disturbances associated with intensive agriculture facilitate the spread of invasive plants that become dominant along habitat edges in fragmented landscapes. Many invasive woody plants offer large quantities of floral resources to bees, but little is known about how invasive plants affect the use of flowering resources in the forest canopy and understory by native bee communities. We sampled the bee community at vertical strata along forest-agriculture edges that varied in density of a dominant invasive shrub Lonicera maackii before, during, and after the flowering period. We also recorded diameters and species identities of woody stems. Bee and woody plant abundance, diversity, and life-history traits were then spatially and temporally compared in response to L. maackii density. Overall, we found that L. maackii structured bee communities through its floral resources by altering bee species composition and supporting greater abundances and species richness of bees during and after its flowering period. We also demonstrated a diverse and abundant bee community up to 16 m high in the forest canopy that is supported by floral resources of native shrubs and trees but sensitive to woody shrub invasion. These findings collectively suggest that this invasive shrub structures the bee community in favor of species that use its own flowers and competes with co-flowering woody species at different vertical strata. Our study emphasizes the importance of forest trees and shrubs for bees in agricultural landscapes and demonstrates potential risks for early-season bees as well as those that cannot use floral resources of this invasive shrub.

Vegetation composition and structure determine wild bee communities in a tropical dry forest

Understanding the factors that influence the composition and structure of bee communities in natural habitats is critical for conservation and restoration efforts, mainly in disturbed ecosystems that are widely used for agricultural crop production, such as tropical dry forests (TDF). The aim of this study was to evaluate the effects of tree species composition and vegetation structure on the composition, abundance and species richness of eusocial and non-eusocial wild bee assemblages. Bees (19.909 individuals of 96 species) were collected in fifteen plots in different secondary succession stages in a TDF in the state of Minas Gerais, Brazil. We found a positive relationship between tree community similarity and bee community similarity, for both eusocial and non-eusocial bees. Average tree height positively affected the abundance and species richness of eusocial bees, while the abundance of non-eusocial bees was negatively affected by tree species richness. Similar tree species composition and vegetation structure between plots at the same stage of secondary succession probably determined more similar bee communities than dissimilar tree communities. Most eusocial bee species are dependent on cavities in large trees to house their colonies, while most non-eusocial bees probably prefer open habitats because they provide a greater density and diversity of floral resources, and suitable areas for ground-nesting species. Since eusocial bees represented 94% of the individuals sampled, the conservation and restoration of mature forests is of primary importance in order to increase eusocial bee diversity, and the maintenance of these areas in the vicinity of agricultural systems is crucial to increase the ecosystem service of pollination.

Animal biodiversity in cider apple orchards: Simultaneous environmental drivers and effects on insectivory and pollination

Making agriculture more sustainable requires a greater understanding of animal-mediated ecosystem services. The beneficial effects of pest-control and pollination provided by, respectively, insectivorous birds and pollinator insects are essential for many crops. Improving these ecosystem services simultaneously in the same crop system means, first, identifying the drivers of animal biodiversity that operate in agricultural landscapes, and second, revealing the relationships between biodiversity and the two services. Here, for two years, we addressed how landscape and small-scale orchard features affected bird and insect biodiversity (abundance and species richness) in cider apple orchards in northern Spain. We examined the effects of bird and insect biodiversity on the magnitude of, respectively, insectivory and pollination. Bird biodiversity was positively affected by the cover of apple canopy within orchards, whereas that of pollinators responded positively to the cover of semi-natural woody habitats and eucalyptus plantations in the surrounding landscape, and also on the level of bloom at the orchard scale. Insectivory, estimated from sentinel model and exclusion experiments, was positively affected by increased abundance and richness of birds across orchards. Similarly, fruit set responded positively to higher abundance and richness of wild bees, whereas seed set mostly depended on the abundance of wild pollinators. Our findings suggest simultaneous positive effects of animal biodiversity on pest-control and pollination in apple orchards, with no sign of trade-offs between biodiversity groups or between ecosystem functions. A multi-scaled management of orchard-level features (apple canopies and surrounding hedgerows for birds, and apple bloom and ground cover for pollinators) and landscape-level ones (surrounding cover of semi-natural woody habitats, moderate for birds, high for pollinators) is encouraged for the simultaneous enhancement of pest-control and pollination. Biodiversity-farming win-win scenarios are possible in cider apple orchards by simultaneously promoting multiple animal-mediated ecosystem services.

Effect of pan trap size on the diversity of sampled bees and abundance of bycatch

Monitoring pollinator health and pollination is among the top priorities to safeguard pollinators and secure pollinator services. Assessments of sampling methods are therefore essential for developing a standardized protocol for long-term pollinator monitoring. Pan trapping is a popular technique to survey pollinators, but limited information is available on the effect of pan trap diameter on the abundance, richness, and body size of sampled bees, as well as on the abundance of bycatch (non-targeted arthropods). We conducted experiments using four diameters of yellow pan traps in three habitats (a semi-natural phrygana habitat, a roadside, and a salt flat) on the Greek island of Lesvos during a 10-day period in late June/early July of 2017 and 2018. We found that pan traps of 4, 7, 10, and 12 cm captured a similar richness of bees and have little or no effect on the abundance estimates of bees and flies. Pan trap diameter did not affect body size of collected bees. Bycatch accounted for 62.8% of the arthropods collected and increased with the diameter of the pan traps in the phrygana and roadside habitats. According to literature, many researchers, especially outside Europe, use pan traps of various diameters (7–34 cm), volumes (96.1–2000 ml), and shapes (round, square, rectangular, or hexagonal). To reduce potential negative effects on populations of other beneficial arthropods, as well as to minimize processing effort and costs, we recommend using small pan traps (7 cm), unless standardized pan trapping protocols have already been adopted.

Redundancy in wildflower strip species helps support spatiotemporal variation in wild bee communities on diversified farms

Wildflower strips are a management practice increasingly used to provide floral resources to wild bees in agroecosystems. Yet, despite known spatiotemporal variation in wild bee communities, the degree to which different wildflower strip species consistently support wild bee communities is poorly understood. Additionally, whether such consistency is related to the functional roles wildflower species play (e.g., in supporting diverse, rare, or unique suites of bee species) has not been considered. Over three years and on four diversified farms, we evaluated spatiotemporal variation in wild bee communities and bee-flower interactions in wildflower strips to better understand the roles of flower strip species in supporting bees. We documented spatiotemporal variation in the abundance, richness, and composition of local wild bee communities. Certain wildflower species consistently supported the highest richness of wild bees across years. These wildflower species were regularly core members of the bee-flower interaction network, visited by both generalist and specialist bees. By contrast, wildflower species supporting the most unique suites of bees were variable in this role among farms. In order to select plant species for wildflower strips that consistently support a high diversity of wild bee communities within farm landscapes, it is useful to consider several different functional roles that plants may play. Whereas a handful of wildflower species may be visited by the majority of local wild bee species, achieving support for the remaining, and perhaps rarer, bee species will require planting additional flower species, which may appear redundant until the spatiotemporal variation in wild bee communities is more thoroughly considered. This functional approach to selecting wildflower species for bee conservation efforts is important for making practical recommendations to land managers and for guiding best management practices in different regions and with diverse management goals.

A comparison of bee communities between primary and mature secondary forests in the longleaf pine ecosystem

Much of the once-dominant longleaf pine (Pinus palustris Mill.) ecosystem has been lost from the Coastal Plain of the southeastern United States and only a few scattered remnants of primary forest remain. Despite much interest in understanding and restoring this ecosystem, relatively few studies have attempted to characterize or assess the conservation status of the longleaf bee fauna. The objective of this study was to compare the diversity and composition of bee communities between primary and mature secondary (>100 years old) fire-maintained forests in Georgia and Florida. We used colored pan traps to sample bees at three primary and four secondary locations divided between two regions characterized by sandy (Eglin Air Force Base) or clayey (Red Hills) soils. There were no overall differences between primary and secondary forests in bee richness, diversity, evenness or abundance. Community composition differed among locations but we found no evidence that primary remnants provide critical habitat to sensitive bee species.

Mass-flowering crops have a greater impact than semi-natural habitat on crop pollinators and pollen deposition

ContextMaximising insect pollination of mass-flowering crops is a widely-discussed approach to sustainable agriculture. Management actions can target landscape-scale semi-natural habitat, cropping patterns or field-scale features, but little is known about their relative effectiveness.ObjectiveTo test how landscape composition (area of mass-flowering crops and semi-natural habitat) and field-scale habitat (margins and hedges) affect pollinator species richness, abundance, and pollen deposition within crop fields.MethodsWe surveyed all flower visitors (Diptera, Coleoptera and Hymenoptera) in oilseed rape fields and related them to landscape composition and field features. Flower visitors were classified as bees, non-bee pollinators and brassica specialists. Total pollen deposition by individual taxa was estimated using single visit pollen deposition on stigmas combined with insect abundance.ResultsThe area of mass-flowering crop had a negative effect on the species richness and abundance of bees in fields, but not other flower visitors. The area of semi-natural habitat in the surrounding landscape had a positive effect on bees, but was not as important as the area of mass-flowering crop. Taxonomic richness and abundance varied significantly between years for non-bee pollinators. Greater cover of mass-flowering crops surrounding fields had a negative effect on pollen deposition, but only when non-bee pollinator numbers were reduced.ConclusionsManagement choices that result in landscape homogenisation, such as large areas of mass-flowering crops, may reduce pollination services by reducing the numbers of bees visiting fields. Non-bee insect pollinators may buffer these landscape effects on pollen deposition, and management to support their populations should be considered.

Habitat area and connectivity support cavity-nesting bees in vineyards more than organic management

The expansion and intensification of agriculture are the main causes of current insect declines. Pollinators like cavity-nesting bees can be limited by reduced nesting and feeding opportunities in farmland. As insects constitute the bulk of terrestrial biodiversity and fulfill important ecological functions, there is an urgent need to identify ways to combine agricultural land use and insect conservation. Perennial crops like grapevine can provide permanent habitats for numerous beneficial organisms including various pollinators. With their dominating character in viticultural areas and >7 million ha covered by vines globally, their potential to contribute to nature conservation should be more widely considered. We compared effects of organic management, inter-row vegetation characteristics and landscape parameters on the abundance and species richness of cavity-nesting bees in Central German vineyards. In a paired study design, we assessed cavity-nesting bees in 15 pairs of organically and conventionally managed vineyards along a gradient of landscape complexity. We found that organic management, even though it enhanced flower availability in the vineyards, was only partially beneficial for cavity-nesting bee abundance. Abundance and species richness were enhanced by either semi-natural habitat area or proximity of woody elements like hedges or forest remnants, most likely due to the nesting demands of this particular group of pollinators. We conclude that vineyards can help to sustain cavity-nesting bee abundance, given that landscapes are managed accordingly. We recommend maintaining or establishing woody elements between vineyards, which is likely to also benefit additional groups of organisms such as breeding birds in viticultural landscapes.