Fig. 7

Inference of historic admixture between Western Speckled Dace populations. We tested for evidence of historic gene flow between diverging populations by measuring the D₃-statistic among population trios. In each case, population A is more closely related to B than to C. D3 measures the discordance in branch lengths with D₃ = 0 means no gene flow, D₃ > 0 indicates gene flow between A and C, whereas D₃ < 0 represents gene flow between B and C. We estimated D₃ statistics for tree topologies where A Coleman Creek was sister to Foskett Spring and Deep Creek and B-C Deep Creek was sister to Foskett Spring and Coleman Creek. We find strong evidence of gene flow (shown by arrows) between Foskett Dace and Coleman Creek (A) and weak evidence of gene flow between Coleman Creek and Deep Creek (B-C). Numbers below each figure indicate mean D₃ for the given topology with 95% CI around the mean given in brackets. Thickness of arrows represents strength of gene flow. These results indicate that Foskett Dace likely diverged most recently from the Coleman Creek population, and that the Coleman Creek population experienced post-divergence gene flow with Deep Creek, possibly via secondary contact