A comparative analysis of mitochondrial DNA genetic variation and demographic history in populations of even- and odd-year broodline pink salmon, Oncorhynchus gorbuscha (Walbaum, 1792), from Sakhalin Island

To assess genetic variation in pink salmon (Oncorhynchus gorbuscha), the polymorphism of nucleotide sequences of the ND2 and Cytb (mtDNA) genes has been analyzed in 404 individuals of even- and odd-year broodlines from 10 temporal samples collected in different years from one river. The data that earlier indicated a high level of genetic differences between samples of the broodlines spawning in even- and odd-numbered years have been confirmed. Genetic differences between samples of early- and late-run fish was detected in a number of cases. A high probability of purifying selection of the studied genes in both broodlines of pink salmon was found using neutrality tests and models based on likelihood methods and Bayesian approach. A median network of haplotypes based on combined mtDNA sequences for even- and odd-year broodlines have revealed the star-like genealogies and the incomplete "sorting" of haplotypes between them. The analysis of distribution of pairwise nucleotide substitutions, neutrality tests, and Bayesian skyline data support the model of expansion for the population of both pink salmon broodlines that occurred at almost the same time. A study of the history of haplotype divergence inferred from the Bayesian chronogram show the similarity of demographic histories in the populations of both broodlines as a reflection of paleoclimate changes in the region.