Population genetic structure and phylogeography of masu salmon (Oncorhynchus masou masou) inferred from mitochondrial and microsatellite DNA analyses.

The population genetic structure and phylogeography of masu salmon were investigated by using variation in the mitochondrial NADH dehydrogenase subunit 5 gene (ND5) and six polymorphic microsatellite loci among a total of 895 fish representing 18 populations collected from Japan (9), Russia (7), and Korea (2) from 2000 to 2008. An analysis of ND5 nucleotide sequences revealed 22 variable sites in about 560 bp in the 5' half of the gene, which defined 20 haplotypes, including some associated with geographical regions. Haplotype and nucleotide diversities were greater in the populations in Japan and Korea than in those in Russia, indicating greater genetic diversity in the Japanese and Korean populations than in the Russian populations. All the microsatellite loci examined showed a high level of variation, but the expected heterozygosity indicated a similar level of genetic diversity among the populations of the three regions, contrary to the results for ND5. However, AMOVA and pairwise population F (ST) estimates for both ND5 and the microsatellite markers indicated a similar pattern of moderate genetic differentiation among populations of the three regions, and large population groups on the coasts of the Sea of Japan, Sea of Okhotsk, and Pacific Ocean in the Far East. From a mismatch distribution analysis and neutrality test, the observed genetic structure appears to have been influenced primarily by bottlenecks during glacial periods and population expansions during interglacial periods in the late Pleistocene.