Population structure and genetic diversity
To summarize population structure, we relied on all LD-filtered autosomal SNPs and used Bayesian clustering as implemented in STRUCTURE v.2.3.4 (Pritchard et al., 2000). We considered K values from 1 to 10. For each K value, we used 20 independent replicates. Each replicate used the first 150,000 iterations as burn-in, followed 150,000 MCMC repetitions. We then used the pophelper (v.2.3.0; Francis, 2017) R package to estimate the most likely number of clusters in our data based on the delta K method (Evanno et al., 2005) and to plot the STRUCTURE results. We supplemented these analyses with a discriminant analysis of principal components (DAPC) performed using theadegenet R package (v. 2.1.1; Jombart & Ahmed, 2011). We further calculated heterozygosity as the percent heterozygous SNPs out of all SNPs with data for a given individual.