Gene flow and dispersal ability of bumble bees in mountain habitats: using genomic methods to test the influence of landscape features

Background/Question/Methods

The ability of species to track changing habitats can be an important component of persistence in the face of climate change. Bumble bee species ranges are changing on a global scale, but many species have not shown range expansion to higher latitudes and elevations at the rate expected based on climate change. This could be due to an inability to disperse to new locations, or to a failure to adapt and survive at new locations. We aim to assess current and historical dispersal of bumble bees through mountain habitats to better understand whether dispersal is limited by landscape features, and which landscape features act to either hinder or aid movement. Our experimental design includes sampling bumble bees from 70 different sites across roughly 40,000 square kilometers in the Columbia and Rocky Mountains. We extracted DNA from two different species of bumble bees, and use single nucleotide polymorphisms (SNPs) to measure relatedness and gene flow to assess dispersal between sites. We test different prediction-based dispersal models including isolation by distance and landscape resistance models against existing patterns of genomic population structure.

Results/Conclusions

We have characterized over 13,000 SNP loci from 186 Bombus melanopygus and 80 Bombus sylvicola individuals. Preliminary results suggest that B. melanopygus may have limited dispersal between foothill and mountain sites, while B. sylvicola populations appear to have genomic separation along a north-south gradient. Understanding how bees have been moving between locations and which landscape features might constrain dispersal will be important in evaluating the ability of bumble bee populations and species to track predicted habitat and range changes in the present and future.