Population structure
Population structure was analyzed using principal components as well as hierarchical clustering analysis. A covariance matrix was calculated using PCAngsd and then we used RStudio v. 1.3.1093 (RStudio Team, 2018) with R v. 3.6.0 (R Core Team, 2019) to conduct eigenvector decomposition and created plots comparing principal components axes (PCs). We used clustering in NGSadmix to infer the “best” number of populations and estimate ancestry proportions. We ran NGSadmix five times each with population numbers (i.e. K values) ranging from one to six. We used the Evanno method implemented in CLUMPAK to determine the best fit K value (accessed at http://clumpak.tau.ac.il/bestK.html).