Host use does not drive genetic structure of mountain pine beetles in western North America

Abstract

The mountain pine beetle (MPB) is one component of an intensively studied co-evolved host-pest system. We investigated the spatial genetic structure of MPB within its historic and recent geographic range expansion as it relates to host use in western North America using 13 pre-selected microsatellite loci. AMOVA shows that genetic structure is not correlated with the host tree species, arguing against the formation of host-race within this species. STRUCTURE analysis shows 4 main clusters in western North America: Northern - Northern British Columbia/Alberta; Central - Southern British Columbia/Alberta/Washington/Idaho/Montana; Southwest - Oregon/California/Nevada and; Southeast - Utah/Wyoming/Arizona/Colorado/South Dakota. Heterozygosity, allelic richness, and number of private alleles is greatest in the Southwest cluster. This cluster correlates with one of the three refugia hypothesized from a recent analysis of neo-Y haplotypes by Dowle and colleagues and represents an important reservoir of MPB genetic diversity.