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1. Conservation insights from wild bee genetic studies: Geographic differences, susceptibility to inbreeding, and signs of local adaptation

   https://doi.org/10.1111/eva.13221  

   Kelemen, Evan P.; Rehan, Sandra M. (March 2021, Evolutionary Applications)

   Abstract Conserving bees are critical both ecologically and economically. Genetic tools are valuable for monitoring these vital pollinators since tracking these small, fast‐flying insects by traditional means is difficult. By surveying the current state of the literature, this review discusses how recent advances in landscape genetic and genomic research are elucidating how wild bees respond to anthropogenic threats. Current literature suggests that there may be geographic differences in the vulnerability of bee species to landscape changes. Populations of temperate bee species are becoming more isolated and more genetically depauperate as their landscape becomes more fragmented, but tropical bee species appear unaffected. These differences may be an artifact of historical differences in land‐use, or it suggests that different management plans are needed for temperate and tropical bee species. Encouragingly, genetic studies on invasive bee species indicate that low levels of genetic diversity may not lead to rapid extinction in bees as once predicted. Additionally, next‐generation sequencing has given researchers the power to identify potential genes under selection, which are likely critical to species’ survival in their rapidly changing environment. While genetic studies provide insights into wild bee biology, more studies focusing on a greater phylogenetic and life‐history breadth of species are needed. Therefore, caution should be taken when making broad conservation decisions based on the currently few species examined. 

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2. Relative bee abundance varies by collection method and flowering richness: Implications for understanding patterns in bee community data

   https://doi.org/10.1002/2688-8319.12071  

   Kuhlman, Marirose P.; Burrows, Skyler; Mummey, Daniel L.; Ramsey, Philip W.; Hahn, Philip G. (May 2021, Ecological Solutions and Evidence)

   Abstract Recent declines in wild bee populations have led to increases in conservation actions and monitoring of bee communities. Pan traps are a commonly used sampling method for monitoring bee populations due to their efficiency and low cost. However, potential biases inherent in different sampling techniques may result in misleading characterizations of bee communities across space and time.In this paper, we examined how bee communities sampled using pan traps and aerial nets changed seasonally, and if they were affected by the availability of floral resources.We found strong seasonal changes in the abundance, but not the richness, of bees captured in pan traps. Notably, we captured the fewest bees during weeks in spring when most flowering plant species were in bloom, suggesting that floral resource availability influences pan trap captures. We also compared patterns of bee abundance in pan traps to those captured by aerial netting. Bee richness in pans and nets was positively correlated, but relative abundances in pan and net samples were dominated by different bee genera. Furthermore, most genera decreased in pans with increasing floral richness, but patterns were mixed for nets. When using presence/absence data, rather than abundance, community composition was more similar between netted and pan‐trapped bee communities and changed less substantially across the floral richness gradient.Overall, these differences led to sampling substantially different bee community compositions in pan traps versus nets, especially when using abundance‐based methods to characterize the bee community. By examining multiple years of intensive seasonal sampling of plant and bee communities, we document potential pitfalls with methods commonly used to sample bee communities.We suggest that pan trapping and aerial netting provide similar estimates of bee species richness and community composition when using presence/absence data, but that practitioners should interpret pan‐trapped bee abundance data with caution especially when comparing bee communities between sites where plant communities may differ. 

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3. A century of wild bee sampling: historical data and neural network analysis reveal ecological traits associated with species loss

   https://doi.org/10.1098/rspb.2023.2837  

   Graham, Kelsey K; Glaum, Paul; Hartert, Joseph; Gibbs, Jason; Tucker, Erika; Isaacs, Rufus; Valdovinos, Fernanda S (August 2024, Proceedings of the Royal Society B: Biological Sciences)

   We analysed the wild bee community sampled from 1921 to 2018 at a nature preserve in southern Michigan, USA, to study long-term community shifts in a protected area. During an intensive survey in 1972 and 1973, Francis C. Evans detected 135 bee species. In the most recent intensive surveys conducted in 2017 and 2018, we recorded 90 species. Only 58 species were recorded in both sampling periods, indicating a significant shift in the bee community. We found that the bee community diversity, species richness and evenness were all lower in recent samples. Additionally, 64% of the more common species exhibited a more than 30% decline in relative abundance. Neural network analysis of species traits revealed that extirpation from the reserve was most likely for oligolectic ground-nesting bees and kleptoparasitic bees, whereas polylectic cavity-nesting bees were more likely to persist. Having longer phenological ranges also increased the chance of persistence in polylectic species. Further analysis suggests a climate response as bees in the contemporary sampling period had a more southerly overall distribution compared to the historic community. Results exhibit the utility of both long-term data and machine learning in disentangling complex indicators of bee population trajectories. 

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4. Diverse Diets with Consistent Core Microbiome in Wild Bee Pollen Provisions

   https://doi.org/10.3390/insects11080499  

   Dew, Rebecca M.; McFrederick, Quinn S.; Rehan, Sandra M. (August 2020, Insects)

   null (Ed.)

   Bees collect pollen from flowers for their offspring, and by doing so contribute critical pollination services for our crops and ecosystems. Unlike many managed bee species, wild bees are thought to obtain much of their microbiome from the environment. However, we know surprisingly little about what plant species bees visit and the microbes associated with the collected pollen. Here, we addressed the hypothesis that the pollen and microbial components of bee diets would change across the range of the bee, by amplicon sequencing pollen provisions of a widespread small carpenter bee, Ceratina calcarata, across three populations. Ceratina calcarata was found to use a diversity of floral resources across its range, but the bacterial genera associated with pollen provisions were very consistent. Acinetobacter, Erwinia, Lactobacillus, Sodalis, Sphingomonas and Wolbachia were among the top ten bacterial genera across all sites. Ceratina calcarata uses both raspberry (Rubus) and sumac (Rhus) stems as nesting substrates, however nests within these plants showed no preference for host plant pollen. Significant correlations in plant and bacterial co-occurrence differed between sites, indicating that many of the most common bacterial genera have either regional or transitory floral associations. This range-wide study suggests microbes present in brood provisions are conserved within a bee species, rather than mediated by climate or pollen composition. Moving forward, this has important implications for how these core bacteria affect larval health and whether these functions vary across space and diet. These data increase our understanding of how pollinators interact with and adjust to their changing environment. 

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5. Harnessing community science to conserve and study ground-nesting bee aggregations

   https://doi.org/10.3389/fevo.2023.1347447  

   Kueneman, Jordan G; Dobler, Cassidy N; Danforth, Bryan N (January 2024, Frontiers in Ecology and Evolution)

   Protecting diverse solitary ground-nesting bees remains a pivotal conservation concern. Ground-nesting bees are negatively impacted by anthropogenic land use change that often removes suitable nesting habitat from the landscape. Despite their enormous ecological and agricultural contributions to pollination, solitary, ground-nesting bees are often neglected, partly due to the significant obstacle of discovering exactly where these bees establish their nests. To address this limitation, we have developed a ‘community science’ project to map aggregations of ground-nesting bees globally. In certain locations, their abundances reach astounding levels, sometimes in the millions, but are scarcely known. Utilizing the iNaturalist platform, which permits geo-referencing of site observations and bee identification, we are providing public education and seeking public engagement to document bee aggregations in order to understand the nesting requirements of diverse species and open new opportunities for their conservation. Conservation priorities may then unequivocally be directed to areas of high species richness, nest densities, and nesting sites of rare bees. Such community-led efforts are vital for successful long-term management of native bees and the biotic and abiotic landscape data from nest-site localities can allow modeling to predict nest-site suitability and to readily test such predictions on the ground. Here, we summarize the progress, current limitations, and opportunities of using a global mapping project (GNBee) to direct conservation efforts and research toward solitary ground-nesting bees. 

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