Fig. 2.

Population differentiation is shown by PCoAs of Nei’s genetic distance from all quality-filtered SNPs (a, c, e) and covariance (Ω) matrices represented as heatmaps (b, d, f), shown for C. punctatus (a, b), P. angulosus (c, d), and S. granularis (e, f). Letters in the PCoAs (a, c, e) correspond to the sample sites shown in Fig. 1, with darker shaded letters corresponding to western sites, and lighter shaded letters corresponding to eastern sites