D3475: A population genomic analysis of a widespread North American bumble bee, Bombus huntii

Bumble bees (genus Bombus) are ecologically and agriculturally important pollinators. As many bumble bees face declining populations, it is increasingly important to identify species of concern, including better understanding taxonomy and phylogeography. Bombus huntii is a widespread North American bumble bee, ranging from Canada to southern Mexico. A previous study using microsatellites by Koch et al. identified signatures of population structure between B. huntii populations in Canada and the U.S. and populations in Mexico. Here, we utilize the newly sequenced chromosome-level B. huntii genome assembly to re-analyze populations from Koch et al. using whole-genome resequencing to gain a better understanding of the population genetic history of the species. We aim to determine if the Mexican populations of B. huntii warrant classification as a separate species from the northern populations. Based on prior results, we would expect to observe the Mexico samples in their own cluster separate from the U.S. and Canada samples if they are distinct species. Our population structure analyses supported previous findings with the U.S. and Canada populations and Mexico populations being split into distinct genetic clusters. Additionally, we present analysis of a whole-genome phylogeny of all samples and outgroups to further test our hypothesis. We also evaluate patterns of genetic diversity, predicting that the Mexican populations will exhibit decreased genetic diversity due to their geographic isolation.