The phylogeography of the asian sockeye salmon Oncorhynchus nerka, inferred from the data on the variability of mitochondrial SNP loci: Analysis of scenarios for post-glacial expansion of the species over the asian coast of the pacific ocean

Abstract

The variability of three single nucleotide polymorphism (SNP) loci in the mitochondrial DNA (mtSNP) is analyzed for sockeye salmon populations over a major part of the species range, from Chukotka to the Kuril Islands. Two basic mtSNP haplotypes, GCC and GTT, have been revealed in 20 sockeye samples from 15 lake–river systems on the Asian coast of the Pacific Ocean. In most of the samples, the ratio of the haplotypes is approximately equal. The GTT haplotype dominates the populations from the Kuril Islands (except Shumshu Island); only the GCC haplotype has been found in the sample from the Commander Islands. This geographic pattern of haplotype distribution was presumably caused by the historico-demographic events related to the formation of the Asian sockeye range in the Middle–Late Pleistocene, viz., fragmentation of the species range and subsequent secondary contact between previously diverged populations. These data provide a basis to consider different scenarios for the formation of the modern diversity of sockeye mtSNP haplotypes, all of which suggest multiple expansions of the species to Asian waters during the periods of oceanic transgression after the Pleistocene glaciations.