Global selection at SNP loci
The global G’ST values for 9 microsatellite and 101 SNP loci across the six populations (221 individuals) were 0.203 and 0.0393, respectively. Per-locus G’ST values ranged from 0.0454 to 0.535 for the microsatellite markers, and from -0.0789 to 0.267 for the SNP markers. Global differentiation patterns showed 94 out of 101 SNP loci to be consistent with stabilizing selection, as their level of divergence was lower than the neutral expectation (Figure 3; Supplementary Material S7). The seven remaining SNP loci showed divergence levels consistent with neutral processes (Figure 3; Supplementary Material S7). The SNP loci showing a global neutral pattern of divergence belonged to four gene function categories: immune response (1 SNP); lipid metabolism (2 SNPs); nervous system development (1 SNP) and reproduction (3 SNPs). We did not detect any SNP loci showing a population divergence pattern consistent with divergent selection across all six populations (i.e., globalG’ST values), possibly due to inconsistent patterns of selection acting among the populations, making a pairwise analysis important to assess divergence patterns.