The bumble bee fauna of Yosemite National Park: Patterns across a large altitudinal gradient

Yosemite National Park in the Sierra Nevada of California is home to 15 species of Bombus (bumble bees and cuckoo bumble bees), more than two-thirds (71%) of the species known from the state. Bombus morrisoni is recorded for the first time on the western slope of the Sierra Nevada. Continued persistence of the isolated alpine population of B. balteatus is documented.  Diversity of bumble bees in Yosemite can be accounted for partly by the 3200m range in elevation from 500m at El Portal to the crest of the Sierra Nevada. Bombus vosnesenskii accounted for 52% of the fauna in our study, and was the most common at all sites, except at the highest elevations (> 2500m). Identifying patterns of abundance and composition of co-occurring species in the context of community structure is a principle activity in ecology. Our study found species diversity remained constant across an elevation gradient, suggesting that community composition is relatively stable. We discuss the potential influence of a species’ biology, namely proboscis length, on the rarity and commonness of bumble bee species in Yosemite.