Native bee species in the United States provide invaluable pollination services. Concerns about native bee declines are growing, and there are calls for a national monitoring program. Documenting species ranges at ecologically meaningful scales through coverage completeness analysis is a fundamental step to track bees from species to communities. It may take decades before all existing bee specimens are digitized, so projections are needed now to focus future research and management efforts. From 1.923 million records, we created range maps for nearly 88% (3158 species) of bee species in the contiguous United States, provided the first analysis of inventory completeness for digitized specimens of a major insect clade, and perhaps most important, estimated spatial completeness accounting for all known bee specimens in USA collections, including undigitized bee specimens. Completeness analyses were very low (3–37%) across four examined spatial resolutions when using the currently available bee specimen records. Adding a subset of observations from community science data sources did not significantly increase completeness, and adding a projected 4.7 million undigitized specimens increased completeness by only an additional 12–13%. Assessments of data, including projected specimen records, indicate persistent taxonomic and geographic deficiencies. In conjunction with expedited digitization, new inventories that integrate community science data with specimen‐based documentation will be required to close these gaps. A combined effort involving both strategic inventories and accelerated digitization campaigns is needed for a more complete understanding of USA bee distributions.

The structural patterns comprising bimodal pollination networks can help characterize plant–pollinator systems and the interactions that influence species distribution and diversity over time and space. We compare network organization of three plant–pollinator communities along the altitudinal gradient of the San Francisco Peaks in northern Arizona. We found that pollination networks become more nested, as well as exhibit lower overall network specialization, with increasing elevation. Greater weight of generalist pollinators at higher elevations of the San Francisco Peaks may result in plant–pollinator communities less vulnerable to future species loss due to changing climate or shifts in species distribution. We uncover the critical, more generalized pollinator species likely responsible for higher nestedness and stability at the higher elevation environment. The generalist species most important for network stability may be of the greatest interest for conservation efforts; preservation of the most important links in plant–pollinator networks may help secure the more specialized pollinators and maintain species redundancy in the face of ecological change, such as changing climate.

Megachilidae is one of the United States’ most diverse bee families, with 667 described species in 19 genera. Unlike other bee families, which are primarily ground nesters, most megachilid bees require biotic cavities for nesting (i.e., wood, pithy stems, etc.). For this group, the availability of woody-plant species may be as important as nectar/pollen resources in maintaining populations. We studied Megachilidae biodiversity in the continental United States. We confirmed that the highest species richness of Megachilidae was in the southwestern United States. We examined the relationship between species richness and climate, land cover, tree species richness, and flowering plant diversity. When examining environmental predictors across the conterminous United States, we found that forested habitats, but not tree diversity, strongly predicted Megachilidae richness. Additionally, Megachilidae richness was highest in areas with high temperature and low precipitation, however this was not linearly correlated and strongly positively correlated with flowering plant diversity. Our research suggests that the availability of nesting substrate (forested habitats), and not only flowering plants, is particularly important for these cavity-nesting species. Since trees and forested areas are particularly susceptible to climate change, including effects of drought, fire, and infestations, nesting substrates could become a potential limiting resource for Megachilidae populations.

To effectively protect wild bee pollinators and the services they provide, it is critical to understand habitat use patterns across a diversity of cover types. Wetlands are underrepresented in bee surveys, and although wetland restoration produces conservation benefits for birds, how hydrological management influences bee assemblages and availability of floral resources is still poorly known. In this study, actively (full or partial water drawdowns) and passively managed restored wetlands in central New York were surveyed to characterize plant and bee assemblages, June–September 2019 and 2020. Over 9,000 bees were collected using pan traps and sweep netting, representing ≥ 109 species in 25 genera. Environmental variables, e.g., percent open water and mudflat frequency, differed among management treatments, and were better predictors of entomophilous plant species composition, bee richness, and/or entomophilous plant richness and occurrence than management treatment alone. Entomophilous plant occurrence varied negatively with invasive graminoid occurrence. Although bee assemblage composition was best explained by phenological turnover, diverse moist-soil flowers in late summer and long-blooming emergent flowers were important to generalists and specialist bees. Emergent wetlands offered valuable floral resources for wild bees, making wetland restoration and management a useful pollinator conservation approach. Maintaining a complex of wetlands by cycling through different hydrological conditions, and controlling densities of invasive plants, can diversify and increase resources available for bees, while also meeting management goals for wetland wildlife.