Genetic Variation and Admixture in the Pallid-Dotted Blue Butterfly (Euphilotes pallescens) within the Great Basin of the Western United States
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Quantifying genomic variation provides information that can be used to understand the evolutionary history of populations. Here, I examined populations of Euphilotes pallescens, a species of butterfly that lives within the Great Basin of western North America. I genotyped 376 butterflies at over 90,000 loci to address questions surrounding gene exchange among lineages of E. pallescens and other geographically proximate Euphilotes species. I also investigated what relative contributions of historical and contemporary admixture to the patterns I saw. I stratified loci into "common" and "rare" loci based on minor allele frequencies to investigate historical and contemporary genetic structure, respectively. I used a Bayesian hierarchical model to visualize and quantify genetic variation in two analyses: one included only E. pallescens populations, while the second analysis was performed at the genus-level. I found evidence of both historical and contemporary gene exchange among subspecies within E. pallescens and among Euphilotes species. However, there was little evidence of a history of admixture between the Great Basin populations of E. pallescens and other Euphilotes species. I also found conflict between the patterns of genomic differentiation in these butterflies and their nominal taxonomy. My investigation of the evolutionary history of these butterflies revealed complex relationships and patterns of gene exchange between lineages that suggest the organization of biological diversity is not always strictly hierarchical and the history of divergence is not always strictly bifurcating.