Recovery Of An Alpine Bombus Community Following Drought-Mediated Population Contractions

Worldwide pollinator decline has increased the urgency of assessing nativepollinator abundance and genetic fitness of existing populations. In 2012, anextreme drought in the intermountain US caused severe population contractionswithin a Bombus community at Pennsylvania Mountain Natural Area, Park County,Colorado. This study aimed to measure the post-drought recovery of the alpineBombus community, measure “effective population size”, and search for evidenceof a corresponding genetic bottleneck.I sampled Bombus workers during 2013 and tested for pre- and post-droughtdifferences in community composition, species diversity and richness, and tonguelength. The 2013-year yielded the highest rate of forager capture, and no change inany community measurements. This suggests that alpine bees may havemechanisms to recover quickly from severe population contractions and that theremay be source populations responsible for replenishing the community.To assess genetic impacts, I genotyped foragers of one species, B. balteatus,following PCR amplification of microsatellite markers. Ne estimates didn’t differfrom pre-drought estimate. None of the bottleneck tests revealed any evidence of agenetic bottleneck in the 2013 Bombus balteatus population. This suggests thatimmigration and dispersal to high alpine mountaintops rates are high, andmountaintops may be less isolated than previously thought.