D3085: Bumble bee parasites in spring queens across an elevational gradient

Elevational gradients are useful for estimating the effects of climate change on species distributions. Bumble bees (Bombus spp.) have annual life cycles, thus parasites must infect an overwintering gyne to persist from year to year. Cold temperatures are often a barrier to the distributions of many parasites, which may expand with increasing temperatures. Using non-destructive sampling, Bombus queens were opportunistically netted across several locations in Boulder County, Colorado, USA from April to June, 2024. Collection sites ranged from 1,500 meters to 3,200 meters. Queen feces were swabbed from petri dishes and placed in cold storage prior to sample processing. After a sample was collected, the queen was identified to species, paint-marked (to avoid recapture) and released. DNA was extracted from the fecal samples, and the prevalence of three common Bombus parasites (Crithidia bombi, Vairimorpha bombi, and Apicystis bombi) was determined through PCR. We predict a decreasing trend in parasite prevalence with elevation; colder winter temperatures may decrease parasite viability and persistence to the next season, while also promoting host health during overwintering. However, queen dispersal distances, under-studied for most North American Bombus species, may interfere with the observed patterns. These data allow us to better understand how climate change will affect the interactions between bumble bees and their parasites.