An assessment of mitochondrial variation in Arctic gadoids

Climatic changes during the quaternary history in Arctic regions have shaped the genetic variation and genealogies of Arctic species. Several studies have been conducted in recent years on genetic diversity of Arctic organisms, but marine fishes are largely underrepresented in these studies. Here, we present a study on mitochondrial variation in three Arctic gadoids: Arctic cod (Arctogadus glacialis), Greenland cod (Gadus ogac), and Polar cod (Boreogadus saida). In addition, geographic variation in Polar cod is presented. The sequence variation at the mtDNA presents similar patterns as observed for other related marine fishes. Variation in these three species reflects rather different historic processes, due to colonization and climatic changes than differences in life histories. In Polar cod, a deeper genealogy is observed and variation is dependent on both latitude and longitude. The deep genealogy indicates either admixture of separate lineages or a population, which has been stable in size during alternating cold and warm periods of the pleistocene.