Genetic population structure and demographic history of a pelagic lumpsucker, Aptocyclus ventricosus

The population structure and demographic history of a pelagic lumpsucker, Aptocyclus ventricosus , were investigated on the basis of sequence variation in the mitochondrial cytochrome b gene (1038 bp). The haplotype network clearly recovered two haplotype groups, consisting of western and eastern North Pacific individuals, except for some specimens collected from offshore of Tohoku, northern Japan. The geographic distribution of haplotypes suggests that the ocean currents in the North Pacific have shaped the population structure of the species after historical vicariant events between the Kuril Islands and Kamchatka Peninsula. In addition, the demographic histories of the two haplotype groups were quite different, suggesting that the western North Pacific group experienced a population expansion starting around 10,000 years ago, while the population size of the eastern North Pacific group has remained more stable.