Faunal composition and species richness differences of bees (Hymenoptera: Apiformes) from two north American regions

Host breadth and global bee species diversity are thought to be linked. Areas where bee species richness is greatest have a greater proportion of oligolectic species and fewer social species. I compared the bee faunas of two North American regions (one mesic, one xeric) and two nearby habitats (riparian and desert scrub). Species richness is greater in the xeric than in the mesic North American region. Despite strongly bimodal bloom in the xeric region and continuous bloom in the mesic region, their bee faunas were similar in the proportion of solitary oligolectic and polylectic bees. Oligolectic species of both areas have short lifespans. Social and cleptoparasitic species made up a greater percentage of the fauna in the mesic North American region. Nearby mesic and xeric habitat both had social species but xeric habitats were richer in oligolectic species. Phylogeny and historical biogeography in combination with ecology of bees and plants will be needed to understand differences of bee faunas