Montane Central Appalachian Forests Provide Refuge for the Critically Endangered Rusty Patched Bumble Bee (Bombus affinis)

Abstract

The mountains of Central Appalachia are rich with environmental variance and host a wide variety of community types and diverse flora and fauna. The once common Rusty-Patched Bumble Bee (RPBB, Bombus affinis) has experienced widespread declines and was believed to have been extirpated throughout the Lower Midwest, Northeast and Appalachian regions of the United States (U.S.). We document the occurrence and environmental associations of a contemporary population within Central Appalachia using a dataset of 274 observations spanning nine years and over 2,000 surveys. We show that Appalachian RPBB are strongly associated with high elevation, heavily forested landscapes, especially those with West to Northwest facing aspects. Measures of forest species composition are also associated with RPBB observations. While only 38 percent of surveys occurred on U.S. National Forest lands, 84 percent of observations occurred in these areas, suggesting distinct forest habitat conditions associated with U.S. Forest Service lands play a role in the persistence of this species. The Appalachian region is rugged and difficult to systematically survey, and our analysis represents the first assessment of the species presence and habitat associations within the region. Appalachian RPBB populations are likely geographically and genetically isolated from Upper Midwest populations and additional research is needed to prioritize future conservation efforts across the current and potential range of the species.