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Bumble bees (genus Bombus) are important pollinators with more than 260 species found worldwide, many of which are in decline. Twenty-five species occur in California with the highest species abundance and diversity found in coastal, northern, and montane regions. No recent studies have examined California bumble bee diversity across large spatial scales nor explored contemporary community composition patterns across the state. To fill these gaps, we collected 1740 bumble bee individuals, representing 17 species from 17 sites (~100 bees per site) in California, using an assemblage monitoring framework. This framework is intended to provide an accurate estimate of relative abundance of more common species without negatively impacting populations through overcollection. Our sites were distributed across six ecoregions, with an emphasis on those that historically hosted high bumble bee diversity. We compared bumble bee composition among these sites to provide a snapshot of California bumble bee biodiversity in a single year. Overall, the assemblage monitoring framework that we employed successfully captured estimated relative abundance of species for most sites, but not all. This shortcoming suggests that bumble bee biodiversity monitoring in California might require multiple monitoring approaches, including greater depth of sampling in some regions, given the variable patterns in bumble bee abundance and richness throughout the state. Our study sheds light on the current status of bumble bee diversity in California, identifies some areas where greater sampling effort and conservation action should be focused in the future, and performs the first assessment of an assembly monitoring framework for bumble bee communities in the state.

Miller-Struttmann et al. (2015) suggest that, in a North American alpine ecosystem, reduced flower abundance due to climate change has driven the evolution of shorter tongues in two bumble bee species. We accept the evidence that tongue length has decreased, but are unconvinced by the adaptive explanation offered. It posits foraging responses and competitive relationships not seen in other studies and interprets phenotypic change as evidence of evolutionary adaptation. By oversimplifying a complex phenomenon, it may exaggerate the potential for bees to quickly adapt to environmental changes.

Many bumble bee species are declining globally from multiple threats including climate change. Identifying conservation priority areas with a changing climate will be important for conserving bumble bee species. Using systematic conservation planning, we identified priority areas for 44 bumble bee species in Canada under current and projected climates (year 2050). Conservation priority areas were identified as those that contained targeted amounts of each species predicted occurrence through climate envelope models, while minimizing the area cost of conserving the identified conservation priority areas. Conservation priority areas in the two periods were compared to established protected areas and land cover types to determine the area of current and future priority sites that are protected and the types of landscapes within priority areas. Notably, conservation priority areas were rarely within established protected areas. Priority areas were most often in croplands and grasslands, mainly within the mountain west, central and Southern Ontario, Northern Quebec, and Atlantic Canada under all climate scenarios. Conservation priority areas are predicted to increase in elevation and latitude with climate change. Our findings identify the most important regions in Canada for conserving bumble bee species under current and future climates including consistently selected future sites. [ABSTRACT FROM AUTHOR]

Section 7 of the Endangered Species Act requires the US Environmental Protection Agency (US EPA) to consult with the Services (US Fish and Wildlife Service and National Marine Fisheries Service) over potential pesticide impacts on federally listed species. Consultation is complicated by the large number of pesticide products and listed species, as well as by lack of consensus on best practices for conducting co‐occurrence analyses. Previous work demonstrates that probabilistic estimates of species' ranges and pesticide use patterns improve these analyses. Here we demonstrate that such estimates can be made for suites of sympatric listed species. Focusing on two watersheds, one in Iowa and the other in Mississippi, we obtained distribution records for 13 species of terrestrial and aquatic listed plants and animals occurring therein. We used maximum entropy modeling and bioclimatic, topographic, hydrographic, and land cover variables to predict species' ranges at high spatial resolution. We constructed probabilistic spatial models of use areas for two pesticides based on the US Department of Agriculture Cropland Data Layer and reduced classification errors by incorporating information on the relationships between individual pixels and their neighbors using object‐based images analysis. We then combined species distribution and crop footprint models to derive overall probability of co‐occurrence of listed species and pesticide use. For aquatic species, we also integrated an estimate of downstream residue transport. We report each separate species‐by‐use‐area co‐occurrence estimate and also combine these modeled co‐occurrence probabilities across species within watersheds to produce an overall metric of potential pesticide exposure risk for these listed species at the watershed level. We propose that the consultation process between US EPA and the Services be based on such batched estimation of probabilistic co‐occurrence for multiple listed species at a regional scale. Integr Environ Assess Manag 2022;18:1088–1100. © 2021 SETAC Key Points: Co‐occurrence assessments of pesticide use areas and listed species ranges mandated by the Endangered Species Act are impaired by data gaps and statistical issues.These co‐occurrence assessments are also inefficient, and a substantial backlog exists.We show that incorporating probabilistic estimates of both pesticide use and species distributions improves these assessments.We also demonstrate that efficiencies may be realized by batch‐processing these assessments for groups of listed species. [ABSTRACT FROM AUTHOR]

Declines of many bumble bee species have raised concerns because of their importance as pollinators and potential harbingers of declines among other insect taxa. At present, bumble bee conservation is predominantly focused on midsummer flower restoration in open habitats. However, a growing body of evidence suggests that forests may play an important role in bumble bee life history. Compared with open habitats, forests and woody edges provide food resources during phenologically distinct periods, are often preferred nesting and overwintering habitats, and can offer favorable abiotic conditions in a changing climate. Future research efforts are needed in order to anticipate how ongoing changes in forests, such as overbrowsing by deer, plant invasions, and shifting canopy demographics, affect the suitability of these habitats for bumble bees. Forested habitats are increasingly appreciated in the life cycles of many bumble bees, and they deserve greater attention from those who wish to understand bumble bee populations and aid in their conservation. [ABSTRACT FROM AUTHOR]

Floral visitor species are often assumed to act either mutualistically towards plants (as pollinators) or to exploit them (as nectar-robbers or as nectar or pollen thieves). We investigated the reproductive biology of pointleaf manzanita ( Arctostaphylos pungens K. Kunth), a regionally abundant North American shrub , in relation to the wide spectrum of behaviours displayed by its flower-visiting insects. We recorded A. pungens populationlevel flowering phenology and nectar standing crop, and conducted experiments documenting its breeding system, in an Arizona upland habitat in 1998 and 1999. Floral visitors were observed over 38 hr. We recorded frequencies of six foraging behaviours within and among individuals of each visitor species. Arctostaphylos pungens flowers in late winter. During this period it is the only abundant floral resource for a diverse array of generalist insects in its habitat. We observed 1206 floral visits by 46 taxa. Most floral visitors pursued mixed behaviours: at the species and/or individual level, they foraged both legitimately and as nectarrobbers or thieves. The most commonly mixed behaviours were legitimate pollen collection (which likely resulted in pollen transfer) and secondary nectar-robbing (which was highly unlikely to do so). As A. pungens was found to be largely self-incompatible, robbing and thieving visits should be detrimental to reproductive success. Although theoretical analyses often assume that exploiters must be punished or excluded for mutualism to persist evolutionarily, exploitation is in fact ubiquitous within cooperative interactions in nature. In manzanita, very few floral visitor species could be classified as exclusively beneficial or detrimental to plants: rather, they exhibited multiple foraging strategies, with no evidence of plant control. Such pollinator-nectar robber spectra appear to be common, and constitute an important challenge to current understanding of how mutualism can persist. [ABSTRACT FROM AUTHOR]