Phylogeography of asian sockeye salmon Oncorhynchus nerka from the data on variability of mitochondrial SNP loci: analysis of scenarios for post-glacial expansion of the species over Asian Pacific coast

Abstract

Variability of three SNP loci allocated in the mitochondrial DNA ( One_CO1, One_Cytb_17, One_Cytb_26 ) is analyzed for sockeye salmon from its different habitats from Chukotka to Kuril Islands. Two basic haplotypes (GCC and GTT) are revealed in 20 samples of sockeye ( n = 33-100) from 15 lake-river systems. Their ratio is mostly equal, but GTT haplotype prevails in the populations from Kuril Islands (except Shumshu Island) and is absent in the sample from Commander Islands. This geographical pattern is presumably caused by historical-demographic events related to the species range formation in the middle-late Pleistocene: fragmentation of the areal and subsequent secondary contact between early diverged populations. Two scenarios are discussed, both with multiple expansions of the species to Asia during periods of oceanic transgression after Pleistocene glaciation. According to one of the scenarios, the GTT haplotype has more ancient origin somewhere on the mainland, whereas the GCC appeared much later in the central Kamchatka refugia. The second scenario presumes the origin of both haplotypes on Beringia Bridge where they diverged in the times of middle-Pleistocene (Wurm) glaciation.