Fig. 4

Evidence for secondary contact over Bass Strait. a TreeMix analysis on the unlinked variants (961 SNPs) allowing for one migration event, showing admixture across Bass Strait from Eden to Melbourne (yellow arrow). The analysis is based on allele frequencies of populations using all individuals. Branch lengths are proportional to the amount of inferred genetic drift. b Results from HyDe analysis showing the strongest signal of introgression between Melbourne and Eden. Only comparisons which were statistically significant after BH correction are shown. For each putative hybrid individual (P2), a Gamma of 0.5 is expected for hybrids between two parental populations (P1, P3), while values closer to 0 indicate a higher contribution is from P1, and values closer to 1 arise from a higher contribution of P3. Fractions under population labels indicate how many individuals of the potential hybrid population showed a significant signal of introgression. c Estimated parameters for the favored scenario using DIYABC Random Forest, supporting secondary contact across Bass Strait. Shown are mean values (quantiles in Additional File 1: Table S2)