Genetic Diversity and Phylogeography of Polar Cod Boreogadus Saida (gadidae) Based on Polymorphism of Mitochondrial Markers in the Pacific Arctic and Beyond

Results of analyses of genetic diversity and phylogeography for polar cod Boreogadus saida in the Pacific Arctic are presented. Analyses leverage polymorphism of Cyt b and COI gene fragments obtained from samples in the Russian Arctic, as well as samples available in open databases. According to these markers, although polar cod demonstrates high haplotype diversity, our results suggest no clear population structure within the Russian Arctic, the Beaufort Sea, and the North Atlantic. This may be explained by the peculiarities of the life cycle of polar cod, particularly oceanographic mechanisms related to the mixing of pelagic eggs and the dispersal of early juveniles by currents and their movement following ice drift within the open waters of the studied area. Results are presented within the context and consideration of existing hypotheses of the origin of the common ancestor of Boreogadus, Arctogadus and Gadus, hypotheses of the divergence of these genera, the formation of the modern range of polar cod and the causes of the genetic diversity of its mitochondrial DNA. We also provide a reconstruction of the evolution of mitochondrial lineages of polar cod, according to one of the possible scenarios of its evolutionary history.