Genetic Variation of Mitochondrial DNA and Demographic History in Coho Salmon (Oncorhynchus kisutch Walbaum, 1792) Populations from Northeastern Russia

To assess the genetic variation of coho salmon (Oncorhynchus kisutch (Walbaum, 1792)) from rivers of northeastern Russia, polymorphism of nucleotide sequences of the NADH dehydrogenase subunit 2 and cytochrome b oxidase mtDNA genes with a total length of 2112 bp was analyzed. In nine samples over different years, 16 haplotypes at 17 polymorphic sites were identified in 133 coho salmon specimens. The purifying selection in the studied genes was detected with a high probability by the Neutrality tests and the Bayesian approximation method. The median network showed the existence of two haplogroups separated by five mutation steps. According to the chronogram inferred from Bayesian dating analysis, the initial stage of divergence of haplogroups began about 182 ka ago. Within the haplogroups, several periods of haplotype divergence were identified within time intervals of 54.3–40.4, 16–12, and 8–7 ka ago. Bayesian skyline data showed an increase in median effective population sizes (NeT) within 10–8 ka ago. The history of haplotype divergence in coho salmon populations reflects paleoclimatic oscillations in the region.