Phylogeography and demographic history of the Pacific smelt Osmerus dentex inferred from mitochondrial DNA variation

The Pacific smelt Osmerus dentex is widely distributed in the North Pacific and Arctic seas and belongs to the species that may shed light on the biogeography and evolutionary history of Arctic marine fauna. O. dentex came into existence in the northwestern Pacific at the Pliocene-Pleistocene border and could widely spread along the Eurasian and North American coasts. We assessed the impact of global climatic and geological changes on the formation of the genetic structure of O. dentex in the Eurasian parts of the species area using a variety of phylogenetic methods and molecular dating. The results were interpreted in conjunction with paleoclimatic evidence. Phylogeographic patterns based on cytb and coI sequences, and RFLP ND3/ND4L/ND4 and A8/A6/COIII/ND3 mtDNA regions for 462 Pacific smelts from 25 Eurasian locations were analyzed. Our results suggest that (1) geographical distribution observed for mtDNA haplotypes resulted from influences of historical range expansions, episodes of long-distance colonization and restricted dispersal; (2) the main refugium was located in the northwestern Pacific and the genetic similarities observed among and within geographical regions probably originated from postglacial recolonization from common sources; (3) an additional small refugium in the White Sea existed in the Late Pleistocene.