Introgressive Hybridization between Southern Asian Dolly Varden, Salvelinus curilus, and Northern Dolly Varden, S. malma malma, on Sakhalin Island

Genetic characteristics of the southern Asian Dolly Varden, Salvelinus curilus, and northern Dolly Varden, S. malma malma, in northeastern Asia and the Aleutian Islands were examined using mitochondrial (mt) and microsatellite (ms) DNA markers. The maximum-likelihood tree based on mtDNA control region haplotypes showed two well-supported monophyletic lineages for these species, but the haplotypes found in the Sakhalin Island populations were an admixture of the two mtDNA lineages. Bayesian clustering using msDNA indicated that all individuals from Sakhalin Island grouped with the S. curilus populations, regardless of their mtDNA haplotype. Incongruence between mtDNA and msDNA markers provided strong evidence of historical mtDNA introgression from S. m. malma to S. curilus. Secondary contact by postglacial colonization from different refugia is a plausible explanation for the introgressive hybridization detected in Sakhalin Island.

Automated summary

The study revealed inconsistent genetic characteristics between the southern Asian Dolly Varden and northern Dolly Varden populations on Sakhalin Island, indicating historical mtDNA introgression. This suggests that introgressive hybridization may have been caused by postglacial colonization from different refugia.