Testing effects of post glacial population structure
Compared to the estimation of divergence time, the fixation indexF ST is more sensitive to gene flow among
populations, where paired populations experiencing gene flow are
expected to have lower F ST values (in a 0 to 1
scale). Therefore, if gene flow occurred across drainage basins after
populations recolonized high elevation areas (i.e. across mountain
ridges), we expect to see little to no discrepancy in comparisons of
populations from the same or different watersheds. For the same set of
population pairs of the best model in the TMRCA analysis, we calculated
the means of Weir & Cockerham’s F ST in VCFtools
version 0.1.17 (Weir & Cockerham 1984, Danecek et al., 2011) using thesemi-filtered dataset . Similar to the TMRCA, the ANCOVA was used
to test whether population pairs from different drainages show higherF ST, with geographic distance between paired
populations as a covariate.