Floral Resources Research Articles

Solitary Bees Host More Bacteria and Fungi on Their Cuticle than Social Bees.

Bees come into contact with bacteria and fungi from flowering plants during their foraging trips. The Western honeybee (Apis mellifera) shows a pronounced hygienic behavior with social interactions, while the solitary red mason bee (Osmia bicornis) lacks a social immune system. Since both visit the same floral resources, it is intriguing to speculate that the body surface of a solitary bee should harbor a more complex microbiome than that of the social honeybee. We compared the cuticular microbiomes of A. mellifera (including three European subspecies) and O. bicornis for the first time by bacterial 16S rRNA and fungal ITS gene-based high-throughput amplicon sequencing. The cuticular microbiome of the solitary O. bicornis was significantly more complex than that of the social A. mellifera. The microbiome composition of A. mellifera subspecies was very similar. However, we counted significantly different numbers of fungi and a higher diversity in the honeybee subspecies adapted to warmer climates. Our results suggest that the cuticular microbiome of bees is strongly affected by visited plants, lifestyle and adaptation to temperature, which have important implications for the maintenance of the health of bees under conditions of global change.

Seasonal variation in urban pollen resource use by north temperate European honeybees

AbstractUrban green infrastructure can provide important habitats for pollinators and support urban ecosystem services. Therefore, these areas must be managed to maximize biodiversity and density of pollinating insects. We used DNA metabarcoding to study honeybee pollen resource use over time and space in the city of Oslo, Norway, and to assess the role of green infrastructure as a resource for pollinators and the services they generate. Urban honeybees used diverse pollen resources throughout their active season. There was considerable seasonal turnover in pollen resource use that reflected flowering phenology. Non-native plants (including invasive species) were an important resource early in the season but were replaced by native plants later in the season. Hive location was not strongly correlated with resource use, likely indicating effective long-distance foraging in the fragmented urban landscape. However, flower visitation rates and floral resource density in public urban green spaces were coupled to pollen use. Honeybees collected pollen from a small number of preferred species but also visited other species, likely for nectar. To preserve pollinator services, urban planning should consider flower resource management, with particular focus on planting native species that can act as early season resources for bees. Public campaigns and other incentive mechanisms to promote the cultivation of native plants that are resources for pollinators and the protection of urban semi-natural habitats have the potential to enhance the value of green infrastructure to support urban pollinators and pollination services.

SolBeePop: A model of solitary bee populations in agricultural landscapes

Abstract With their large diversity of species, solitary bees are important pollinators of crops and native plant communities in agricultural landscapes. Stressors such as changing landscapes, climate and pesticide exposures may affect populations differently, dependent on each species' ecological traits. We developed a population model for solitary bees, SolBeePop, which can be applied to simulate a variety of species by using species‐specific traits, including the nesting strategies. Species' phenological traits are mechanistically combined with input time series capturing temporal and spatial variability in landscape compositions. Calibration and validation of the model with empirical study data demonstrate that the model can capture realistic dynamics in bee populations. In simulations conducted representing four species, Osmia bicornis, Megachile rotundata, Nomia melanderi and Eucera pruinosa, identical conditions and assumed nesting resource limitations resulted in different population‐level outcomes, indicating the importance of interactions between external factors and species‐specific traits including phenological, survival and reproductive traits. Synthesis and applications. The publicly available model is intended as a tool for the assessment of population‐level outcomes of stressors, for instance, the limitation of floral resources in agricultural landscapes, limitation of nesting habitat and the exposure to pesticides. Realistic landscape scenarios can be tested and available data for one species can be used to estimate outcomes in other solitary bee species, informing conservation plans and risk assessment approaches to support managed and natural populations in the field.

Floral preferences of carpenter bees (Apidae: Xylocopini: Xylocopa) from Maranhão, Northeast Brazil

ABSTRACT The current study aimed to recognize the floral resources used by bees of the genus Xylocopa in transition physiognomies. We compiled the information available from biological collections and analyzed metrics of dystrophic interaction. We listed 2547 records of Xylocopa in flowers, across twelve identified bee species. The bees were collected from 109 plant species, belonging to 77 genera and 36 families. An interaction network was constructed based on 193 interactions. In which there was a significant correlation between the abundance of bees collected and the richness of plants visited. The most generalist bees were X. cearensis and X. frontalis, and the plants with the most records were Chamaecrista hispidula and C. ramosa. Significant seasonality was observed in the total number of individuals. On the other hand, there was a weak similarity among Xylocopa species according to plant species, despite the clear relationship of the bees according to physiognomies. The interaction network proved to be highly nested, indicating a functional partitioning that allows several species to occur in the same environment. The contribution made by the current work for its regional scope stands out, dealing with areas that have distinct characteristics.

Floral resources of Epicharis flava (Hymenoptera, Apidae) in an urban area, detected from the pollen spectrum in the scopae

Bees are the main pollinators of terrestrial ecosystems and, among them, we can highlight oil-collecting bees, which show different morphological and behavioral adaptations associated with plants that offer this floral resource. Floral oils are used in provisioning, building, and lining the brood cell and nests. The genus Epicharis has a neotropical distribution and females are closely associated with plants of the Malpighiaceae family, with the highest number of records in species of the genus Byrsonima. However, due to the strong seasonality of adult activity and solitary behavior, knowledge about important floral resources to Epicharis bees is still scarce. In order to identify important resource sources for a widely distributed species, the current work aimed to analyze the pollen spectrum of Epicharis flava Friese in an urban area in the Atlantic Forest domain. For this, females of E. flava were captured during five days while visiting flowers of Byrsonima sericea DC. (Malpighiaceae) in an urban area, and the pollen load in their scopae was submitted to acetolysis processing for further analysis under the microscope. In total, 71 pollen types were found, with emphasis on Fabaceae, Solanaceae, Bignoniaceae, and Malpighiaceae, considered sources of nectar, pollen, and floral oils. This study made it possible, through the analysis of pollen in the scopae, to identify a list of potentially important species for the maintenance of E. flava populations. This information is necessary for the management of urban green areas, aiming at increasing biodiversity. In addition, these data can serve as a base for further research on oil-collecting bees in the Neotropics.

Fire regime shapes butterfly communities through changes in nectar resources in an Australian tropical savanna

AbstractFire‐dependent savanna provides key habitat for butterflies globally, but we know little about how fire regimes, including fire frequency and season, affect them. These impacts are likely to be primarily indirect, through changes in overall habitat structure, the abundance of larval host plants, and/or the provision of nectar resources for adults. We examined the relationships among fire regime, butterfly abundance and diversity, and vegetation structure and floral resources within a long‐term fire experiment near Darwin in the Australian monsoon tropics. We surveyed butterflies and floral resources throughout the 2019–2020 wet season in three replicate plots of each of six experimental treatments that had been operating for 15 years. All plots subject to fire had been burned in the previous dry season. We observed 24 butterfly species and 280 individuals representing all five butterfly families found in Northern Australia. Butterfly abundance was highest under early dry‐season (June) fire regimes (mean = 11.9 individuals per plot survey) compared with a late dry‐season (October) regime (mean = 6.7) and in the long‐term absence of fire (mean = 5.3), and this was correlated with the abundance of floral resources. The distribution of butterflies was also highly associated with floral resources within plots regardless of fire treatment. Butterfly species richness was significantly higher in early dry‐season (mean = 6.8) compared with unburned (mean = 3.3) plots but did not differ between early and late dry‐season (mean = 4.7) plots. Butterfly and floral diversity were similar across all early dry‐season fire treatments regardless of whether they had been burned every 1, 2, 3, or 5 years. Our finding that early dry‐season burning promotes butterfly diversity and abundance by increasing the supply of nectar resources has important implications for biodiversity management more broadly, given that nectar is a critical resource for many animal taxa.

Religious and Cultural Use of Plant Resources by Baram Tribe

Plants have been used by the humans since the ancient times. Indigenous people have sound knowledge of using floral species in their cultural rituals and customs. The use of such resources depends on indigenous knowledge gained from ancestral experience. So this study was carried out to explore the traditional use of plant species in their culture and religious customs of Barams in their ancestral place (Barpak-Sulikot Municipality of the Gorkha district) under ethnographic research design. Total of six elder people having the socio--cultural knowledge (are also the healers) were selected purposively for the study. In-depth interview and observation with ethic perspective was done frequently from 2076 to 2078 BS. Following the qualitative technique of data analysis, information was analyzed and interpreted thematically. The result shows that Barams have rich indigenous knowledge of using plant resources. They depend on floral resources for medicine, food, fodder, timber and firewood etc. aligning with the cultural and religious use. Total of 29 species were used in total of six worships or festivals and total of 13 species were used in four different cultural rituals of the Baram.

A spatially explicit model of landscape pesticide exposure to bees: Development, exploration, and evaluation

Pesticides represent one of the greatest threats to bees and other beneficial insects in agricultural landscapes. Potential exposure is generated through compound- and crop-specific patterns of pesticide use over space and time and unique degradation behavior among compounds. Realized exposure develops through bees foraging from their nests across the spatiotemporal mosaic of floral resources and associated pesticides throughout the landscape. Despite the recognized importance of a landscape-wide approach to assessing exposure, we lack a sufficiently-evaluated predictive framework to inform mitigation decisions and environmental risk assessment for bees. We address this gap by developing a bee pesticide exposure model that incorporates spatiotemporal pesticide use patterns, estimated rates of pesticide degradation, floral resource dynamics across habitats, and bee foraging movements. We parameterized the model with pesticide use data from a public database containing crop-field- and date-specific records of uses throughout our study region over an entire year. We evaluate the model performance in predicting bee pesticide exposure using a dataset of pesticide residues in pollens gathered by bumble bees (Bombus vosnesenskii) returning to colonies across 14 spatially independent landscapes in Northern California. We applied alternative model formulations of pesticide accumulation and degradation, floral resource seasonality, and bee foraging behavior to evaluate different levels of detail for predicting observed pesticide exposure. Our best model explained 73 % of observed variation in pesticide exposure of bumble bee colonies, with generally positive correlations for the dominant compounds. Timing and location of pesticide use were integral, but more detailed parameterizations of pesticide degradation, floral resources, and bee foraging improved the predictions little if at all. Our results suggest that this approach to predict bees' pesticide exposure has value in extending from the local field scale to the landscape in environmental risk assessment and for exploring mitigation options to support bees in agricultural landscapes.

Grassland extensification enhances nest densities of ground‐nesting wild bees

Abstract Ground‐nesting wild bees provide essential pollination services in agroecosystems, but they are jeopardized by intensive agricultural management. To mitigate such negative impacts, agri‐environment schemes have been implemented. While the success of enhancing floral food resources is relatively well studied, the role of agri‐environmental schemes in providing suitable nesting habitat remains underexplored. We studied the effectiveness of meadow extensification according to the Swiss agri‐environment scheme in promoting nesting of ground‐nesting bees. Using a paired design, we quantified their nests during four rounds (March–June) in pairs of nine randomly selected extensively (i.e. no fertilizer input, postponed first mowing) and nine intensively managed meadows with similar soil properties, slope, exposure and landscape context. Nest numbers and vegetation characteristics were surveyed in areas of 250 m2. Vegetation properties were also assessed in 0.5 × 0.5 m plots around nest locations and randomly selected locations without nests within each meadow to assess their role as drivers of nesting incidence (nest presence/absence) at this plot scale. We found substantially higher nest numbers of ground‐nesting bees in extensively (mean ± SE per sampling round = 46.8 ± 14.2) compared to intensively managed meadows (0.8 ± 0.3; no nests in three of nine intensively managed meadows). Extensively managed meadows harboured nests of several dominant crop pollinator species, including aggregations of, for example, Lasioglossum malachurum contributing to high nest densities in some of them. Number of nests was negatively related to grass cover and vegetation height, which were lower in extensively compared to intensively managed meadows. Plot‐level nesting incidence increased with bare ground and moss cover, and decreased with grass cover. Synthesis and applications. Our study shows that extensively managed meadows are better nesting habitats for ground‐nesting bees than intensively managed meadows, if reduced management intensity is associated with altered vegetation characteristics such as reduced grass cover and vegetation height, and small‐scale availability of bare ground, driving these effects. This highlights that maintaining and promoting extensive management of meadows can promote ground‐nesting wild bees, including dominant crop pollinators, not only by enhancing floral resources but also by improving nesting opportunities in agroecosystems.

Assessing five decades of garden bee studies

Urban garden spaces are potentially important habitats for bee conservation. Gardens can host diverse flora, which provide floral resources across foraging seasons for bee species. Recent reviews have focused on the impacts of cityscapes on urban bee assemblages in different green spaces. Urban gardens are distinct from other urban green spaces, and bee communities in urban spaces have been an increasing topic of study over the past few decades. We reviewed 28 urban garden bee studies spanning five decades and 14 countries to compile an original metadataset of bee species' functional traits to understand the conservation value of gardens, identify gaps in bee sampling efforts, and summarize the calls to action included by their authors. Studies of urban garden bees have documented between 674 (conservative count, excluding morphospecies) and 830 (liberal count, including morphospecies) bee species. Urban garden bee communities were taxonomically and functionally diverse, although bee species that were non-eusocial, ground-nesting, generalist foragers, and native were most common in garden habitats. The proportion of parasitic bee species and specialist foragers found in urban gardens was comparable to proportions for global bee taxa. This suggests that gardens contain the hosts and forage needed to support bees with specialized life history requirements, and thus represent high quality habitat for a subset of bee communities. Garden bee research was strongly biased toward the northern hemisphere, which signifies a large gap in our understanding of garden bee communities in other regions. The variety of, and non-standard sampling methods in garden bee research makes it difficult to directly compare results between studies. In addition, both intentional low taxonomic resolution and a lack of collaboration with taxonomists constrains our understanding of bee diversity. Our analyses highlight both successes of past urban garden bee studies, and areas of opportunity for future research as we move into a sixth decade of garden bee research.

Pollen sources of Asian honeybee (Apis cerana Fabricius) in Paschim Medinipur district of West Bengal, India

The Asian honeybee (Apis cerana) occurs across the south, southeast and east Asia. The species is utilised in apicultural practices. But the available documents about their floral resources, especially pollen sources, are limited. However, it is a mandatory requirement in a sustainable honeybee management programme. In the present study, we conducted palynological analyses of pollen loads and field surveys to determine pollen sources for the honeybees in West Bengal, India. The honeybee species is regarded as a generalist forager with significant floral constancy supported by homogenous pollen loads with diverse pollen types (here 58). Important pollen-contributed plants were Acacia auriculiformis, Brassica juncea, Cocos nucifera, Eucalyptus sp., Neolamarckia cadamba, Peltophorum pterocarpum, Sesamum indicum and Tridax procumbens. In the semi-urban area of Midnapore town, honeybees mainly depend on planted trees and weeds for pollen sources. While in rural agricultural belts, they also visited wild trees and several cultivated crops. The bee-visited plants are diverse types regarding plant habits, flowering phenology and floral characteristics. These data will be helpful in the management of Asian honeybees, providing pollination services to cultivated crops and thereby enhancing crop yield.

Heather pollen is not necessarily a healthy diet for bumble bees

There is evidence that specialised metabolites of flowering plants occur in both vegetative parts and floral resources (i.e., pollen and nectar), exposing pollinators to their biological activities. While such metabolites may be toxic to bees, it may also help them to deal with environmental stressors. One example is heather nectar which has been shown to limit bumble bee infection by a trypanosomatid parasite, Crithidia sp., because of callunene activity. Besides in nectar, heather harbours high content of specialised metabolites in pollen such as flavonoids but they have been poorly investigated. In this study, we aimed to assess the impact of Crithidia sp., heather pollen and its flavonoids on bumble bees using non-parasitised and parasitised microcolonies fed either control pollen diet (i.e., willow pollen), heather pollen diet, or flavonoid-supplemented pollen diet. We found that heather pollen and its flavonoids significantly affected microcolonies by decreasing pollen collection as well as offspring production, and by increasing male fat body content while parasite exposure had no significant effect except for an increase in male fat body. We did not find any medicinal effect of heather pollen or its flavonoids on parasitised bumble bees. Our results provide insights into the impact of pollen specialised metabolites on heather-bumble bee-parasite interactions. They underline the contrasting roles of the two floral resources for bumble bees and emphasize the importance of considering both nectar and pollen when addressing medicinal effects of a plant for pollinators.

The value of twinned pollinator-pollen metabarcoding: bumblebee pollination service is weakly partitioned within a UK grassland community

Predicting ecological impact of declining bumblebee (Bombus) populations requires better understanding of interactions between pollinator partitioning of floral resources and plant partitioning of pollinator resources. Here, we combine Cytochrome Oxidase 1 (CO1) barcoding for bumblebee identification and rbcL metabarcoding of pollen carried by bees in three species-rich UK pastures. CO1 barcoding assigned 272 bees to eight species, with 33 individuals belonging to the cryptic Bombus lucorum complex (16 B. lucorum and 17 B. cryptarum). Seasonal bias in capture rates varied by species, with B. pratorum found exclusively in June/July and B. pascuorum more abundant in August. Pollen metabarcoding coupled with PERMANOVA and NMDS analyses revealed all bees carried several local pollen species and evidence of pollen resource partitioning between some species pairings, with Bombus pratorum carrying the most divergent pollen load. There was no evidence of resource partitioning between the two cryptic species present, but significantly divergent capture rates concorded with previous suggestions of separation on the basis of foraging behaviour being shaped by local/temporal differences in climatic conditions. Considering the bee carriage profile of pollen species revealed no significant difference between the nine most widely carried plant species. However, there was a sharp, tipping point change in community pollen carriage across all three sites that occurred during the transition between late July and early August. This transition resulted in a strong divergence in community pollen carriage between the two seasonal periods in both years. We conclude that the combined use of pollen and bee barcoding offers several benefits for further study of plant-pollinator interactions at the landscape scale.

Enhancing Coccinella Beetle Biological Pest Control via a Floral Approach in Cucumber Greenhouse.

Flower-rich habitats are crucial for promoting biodiversity and ecosystem services within agricultural ecosystems, such as pollination and pest control. The present study investigates the efficacy of employing floral structures as a criterion for the selection of plant species in order to enhance the attraction of natural enemies within cucumber greenhouses, consequently augmenting floral resources. The results of our study provide evidence that flower strips have a beneficial effect on the fitness of critical natural predators, while not facilitating the proliferation of detrimental insect species. These findings exhibit potential for enhancing pest-management services in the agricultural sector. The findings of our study demonstrate that pest levels within greenhouse environments closely resemble those observed in real-world commercial cropping systems. As a result, the introduction of Coccinella septempunctata and Menochilus sexmaculatus biocontrol agents is confirmed to be a reliable and efficient method for pest management. The phenomenon of predator-prey density dependency is recognized as a crucial element in the implementation of biological control strategies. Furthermore, we investigate the impact of floral resources on the reproductive capacity of indigenous predators. The impact of Coriandrum sativum on fertility is substantial, indicating that the presence of a varied plant assortment with overlapping flowering periods can prolong the availability of floral resources. This study highlights the significance of flower-rich habitats and deliberate plant selection in augmenting biodiversity, ecosystem services, and pest management within agricultural settings. The implementation of conservation biological control technologies presents supplementary ecological advantages, thus offering practical implications for the promotion of sustainable agricultural practices.

Conserved, yet disruption-prone, gut microbiomes in neotropical bumblebees.

Social bees are an important model for the ecology and evolution of gut microbiomes. These bees harbor ancient, specific, and beneficial gut microbiomes and are crucial pollinators. However, most of the research has concentrated on managed honeybees and bumblebees in the temperate zone. Here we used 16S rRNA gene sequencing to characterize gut microbiomes in wild neotropical bumblebee communities from Colombia. We also analyzed drivers of microbiome structure across our data and previously published data from temperate bumblebees. Our results show that lineages of neotropical bumblebees not only retained their ancient gut bacterial symbionts during dispersal from North America but also are prone to major disruption, a shift that is strongly associated with parasite infection. Finally, we also found that microbiomes are much more strongly structured by host phylogeny than by geography, despite the very different environmental conditions and plant communities in the two regions.

Examining spatial and temporal drivers of pollinator nutritional resources: evidence from five decades of honey bee colony productivity data

Pollinators are an essential component of terrestrial food webs and agricultural systems but are threatened by insufficient access to floral resources. Managed honey bees, as generalist foragers that hoard nectar as honey, can act as bioindicators of floral resources available to pollinators in a given landscape through their accumulation of honey. Honey yields across the United States have decreased appreciably since the 1990s, concurrent with shifts in climate, land-use, and large-scale pesticide application. While many factors can affect honey accumulation, this suggests that anthropogenic stressors may be having large-scale impacts on the floral resources that pollinators depend on for their nutrition. We used hierarchical partitioning on five decades of state-level data to parse the most important environmental factors and likely mechanisms associated with spatial and temporal variation in honey yields across the US. Climatic conditions and soil productivity were among the most important variables for estimating honey yields, with states in warm or cool regions with productive soils having the highest honey yields per colony. These findings suggest that foundational factors constrain pollinator habitat suitability and define ecoregions of low or high honey production. The most important temporally varying factors were change in herbicide use, land use (i.e. increase in intensive agriculture and reduction in land conservation programs that support pollinators) and annual weather anomalies. This study provides insights into the interplay between broad abiotic conditions and fine temporal variation on habitat suitability for honey bees and other pollinators. Our results also provide a baseline for investigating how these factors influence floral resource availability, which is essential to developing strategies for resilient plant–pollinator communities in the face of global change.

Spontaneous flowering vegetation favours hoverflies and parasitoid wasps in apple orchards but has low cascading effects on biological pest control

Floral resources support several ecosystem services in agroecosystems, such as pollination or biological control. Many beneficial organisms feed on nectar or pollen for an important part of their life cycle. Providing adequate and sufficient floral resources through the conservation of spontaneous flowering vegetation may be a strategy to improve biological pest control. However, the role of spontaneous flowering plant species has mainly been evaluated in the recruitment of natural enemies. Cascading effects on pest regulation and damage reduction are rarely studied. Here we evaluated the effect of spontaneous flowering vegetation on pest regulation in 18 Mediterranean apple orchards. We focused on two main apple pests, Cydia pomonella and Dysaphis plantaginea, and on two groups of their natural enemies depending on floral resources: hoverflies and parasitoid wasps. We combined generalised linear mixed models and piecewise structural equation models to test for direct and indirect effects of spontaneous flowering plant species on beneficial insects (hoverflies, parasitoid wasps, wild bees and honeybees) and on pest regulation. We also tested for potential negative interactions between honeybees and hoverflies, parasitoid wasps or wild bees. There was a positive and significant effect of insect-pollinated flowers on hoverflies, parasitoid wasps and bees, but small cascading effects on D. plantaginea or C. pomonella density and associated damage. There was no significant relationship between honeybees and hoverflies, parasitoid wasps or wild bees. The reduction of D. plantaginea infestation was partially mediated by hoverfly abundance. Furthermore, we observed effects of spontaneous flowering vegetation on pest regulation and damage reduction independent of hoverfly and parasitoid wasp abundances. These results highlight the importance of conserving floral resources to support biological control of apple pests. Further studies are needed to better understand interactions between spontaneous flowering vegetation and crop management practices to promote sustainable pest regulation strategies.

Urban parks as a functional area for the maintenance and diversity of bee populations

Urbanization restricts native vegetation to small fragments surrounded by paved areas, grasses and degraded areas that strongly affects several biotic communities, including pollinator populations, which are not only greatly affected, but are also declining in several parts of the world. Bees are considered to be the main organisms to perform pollination, as they need to visit a great number of flowers daily to satisfy their individual food needs, their offspring and their colony, since they depend on floral resources at all stages of their life. Thus, the aim of this study was to verify the effectiveness of urban parks as refuges for bee species, having its veracity as a hypothesis. It was considered to evaluate the diversity of bees and their foraging activities in plant species in two urban parks over a year located in the city of Dourados-MS/Brazil. Sampling was performed every two weeks, from 8:00 a.m. to 4:00 p.m. for 13 months, from 2019 to 2020. For this purpose, active samplings were carried out with an aerial entomological net. Bee species were found distributed in 5 families: Apidae, Halictidae, Colletidae, Megachilidae and Andrenidae. Apis mellifera was the most abundant species followed by Trigona spinipes. Considering the two parks, 34 species of bees visiting 33 plant species were sampled. Results suggest that urban parks represent a significant area for maintenance of bee populations in the city of Dourados - MS, protecting a very diverse fauna, confirming the hypothesis that urban parks represent relevant and functional areas for bees, helping in the diversity maintenance of these pollinating organisms.

Long‐term organic farming and floral diversity promotes stability of bee communities in agroecosystems

Abstract Increasing bee diversity promotes pollination services on farms. Yet, given the high turnover in pollinator communities, without knowledge of how pollinator communities assemble, it is difficult to conserve or increase bee diversity. Thus, a mechanistic understanding of factors mediating pollinator community assembly could promote pollinator conservation measures. To assess the determinants of pollinator community assembly and structure, we surveyed bee communities and floral resources on 36 farms ranging from 0 to 43 years in organic production. We used niche‐based and stochastic species abundance models to characterise the mechanisms driving community assembly, and an additive partition of beta diversity to evaluate resource and species turnover (i.e. community structure). We then used statistical models to assess whether resource turnover or time in organic production altered community assembly and beta diversity, and a jackknife analysis to assess the sensitivity of top models to resource and species identity. We show that bee communities on farms that practiced organic methods for longer assembled by niche‐based rather than stochastic processes and had less turnover in bee species across years. Because our model of niche‐based processes assumes resource use, these results indicate bee communities reflect underlying species‐specific resource preferences (e.g. floral and/or nesting resources) and that longer periods of organic management reduced dissimilarity mediated by species replacement. Our jackknife approach then examined the role of species identity effects in beta diversity, showing changes in floral resources increased dissimilarity driven by bee species loss, but only in landscapes simplified by urbanisation. This jackknife analysis then indicated that landscape resource replacement which was not driven by particular landscape classes, mediated bee species replacement wherein dissimilarity was driven by a generalist native bee, suggesting bee life history (e.g. flexibility in resource use) and landscape complementarity, rather than identity, underlie patterns identified using the beta diversity equations. Our results show bee communities assemble by niche‐based processes, evidenced by collinearity in resource and bee species turnover. Because niche‐based assembly indicates ecosystem health, farmers who adopt crop diversification and practice organic methods for longer may promote pollinator diversity and stability leading to improved pollination in farms. Read the free Plain Language Summary for this article on the Journal blog.

Diverse forest management strategies support functionally and temporally distinct bee communities

Abstract Forests worldwide support insect biodiversity and the ecosystem services provided by insects such as pollination. As forest health declines, management that emulates historical disturbance regimes has the potential to restore and maintain forest ecosystem functioning; however, we lack understanding of how these practices affect key mutualists like bees and the ecosystem services they provide. To fill this knowledge gap, we investigated the functional response of bee communities to temperate deciduous forest management practices that emulate historical disturbances (burning, thinning and the combination of the two). We also investigated whether seasonality has any effect on this relationship. Bee functional diversity was highest in spring compared to summer, and management did not affect this relationship. Instead, different management strategies aligned with specific bee functional traits and these relationships varied throughout the year. Managed and unmanaged areas differed in the distribution of nesting and floral resources and, as a result, altered bee functional trait composition. Thinned plots with increased floral resources promoted smaller bees with limited dispersal capacity, in addition to primitively eusocial and cavity‐excavating bees. Unmanaged habitat supported vulnerable bee groups such as cleptoparasites and specialists. Burning by itself or in combination within thinning may have eliminated crucial nesting resources such as deadwood that bees depend on in forests. Synthesis and applications: Our findings demonstrate that managing temperate forests by emulating historical disturbances can support a functionally diverse bee community and highlight the need to consider temporal variation in the environmental drivers of forest bee communities. To support year‐round bee diversity, forest management strategies should prioritize floral resources and leave behind deadwood to increase bee nesting resources, as well as maintain unmanaged habitat within the forest landscape. Overall, our study reinforces the importance of using a range of forest management strategies to enhance bee functional diversity and associated ecosystem services.