1st Place: D3084: Bumble bee pathogens across an urban to rural gradient

Bumble bees are important pollinators of economically significant crops but in the past 20 years, there has been a decline in several North American species, including the federally endangered rusty patched bumble bee (Bombus affinis). Once common throughout its range in the upper Midwest and Eastern U.S., B. affinis is now absent from 87% of its historical range. Pathogens, particularly those originating from commercial colonies, have been implicated in this decline and are an immediate concern for conservationists. However, pathogen distribution across the rusty patched bumble bee’s range and how land use affects pathogen prevalence is unknown. Madison, WI is a large metropolitan area, within the extant range of the rusty patched bumble bee and is bordered by suburbs, exurbs, agriculture, and forested areas. Approximately 2,100 bees were collected from 20 sites along an urban to rural gradient during the summer of 2019 and 2020. We screened each bee for 3 microparasites (Vairimorpha sp., Crithidia sp., and Apicystis sp.) using a multiplex PCR panel. Conopidae sp. (Order Diptera) and Mermithidae sp. (Order Mermithida), both large endoparasitoids, were found in nearly 12% of collected bees. Microparasite prevalence varied across sites. Bombus impatiens, the most abundant species, had the highest pathogen prevalence. This study was the first to document the pathogen profile across a land-use gradient within the rusty patched bumble bee’s current range.