Population genetic diversity patterns of bumble bee (Bombus) communities in the wild lands of the Pacific Northwest

Illuminating the relationship between environmental variation and the distribution of genetic diversity is one of the underlying goals in biodiversity studies. Genetic diversity is the raw material of evolution, a reflection of neutral and adaptive processes shaping the fitness and ultimate survival of a population or species. Maintenance of genetic diversity is strongly driven in part by dispersal-mediated gene flow across wild populations. In this study we estimate population genetic structure and diversity of bumble bees (Hymenoptera: Apidae, Bombus) distributed across an elevation gradient in the Pacific Northwest of the United States with 15 microsatellite loci. We predict that high elevation species will experience reduced gene flow among populations due to decreased habitat suitability and increased resistance to disperse across suitable habitats. Our results reveal that genetic differentiation and diversity are largely determined by a species’ distribution, with bumble bee species limited to high elevations found to exhibit significant pair-wise genetic differentiation across geographic distance. As bees are critically important pollinators of wild land plants, we discuss the implications of global climate change on their ability to sustain ecological services.