Bee species in the genus Andrena (Hymenoptera: Andrenidae) isolated to sky islands of the southwestern United States and Mexico

The genus Andrena (Andrenidae) is a species rich group of ground nesting solitary bees containing ~1,500 species worldwide and with many species left to be discovered. There are about 500 species of Andrena in the United States. Sky Islands are high elevation mountain areas that have distinctly different vegetation and climates compared to the low elevations below them. Throughout the Southwestern United States and the inland areas of North to Central Mexico there are many of these high elevation Sky Island mountains scattered throughout vast stretches of low elevation desert environments. However, the melittofauna from these mountain areas are still poorly known. During this study, we discovered six species of Andrena isolated to these Sky Island environments. Two of these species have strong evidence of being isolated completely to these environments, while three other species seem to be geographically isolated , but possess less locality records to support this claim. The distribution of the remaining species is ambiguous but locality data generally supports isolation. Evidence for what is keeping these species isolated to these Sky Islands, as well as how these species became isolated, is addressed. This research has opened many potential future research opportunities including species origins, diversification, genetics/gene flow between populations, and implications of climate change on these Sky Island environments.