High genetic connectivity and Population Expansion of Scomber japonicus in the Northern Humboldt Current System revealed by mitochondrial control region sequences

The chub mackerel, Scomber japonicus supports an important fshery in the Southeast Pacifc, however, its population genetics is currently unknown. In the present study, we examined the genetic structure, the gene flow and the historical demography of this species in the Northern Humboldt Current System. Samples were collected during summer of years 2013-2014 from three fshing points (Paita, Ventanilla and Ilo), covering 12 degrees of latitude along the coast of Peru. A 532 bp segment of the mitochondrial control region was sequenced in 72 individuals, which allowed us to detect a total of 29 polymorphic sites, 35 haplotypes, moderate-to-high levels of haplotype diversity (0.793-0.969) and very low levels of nucleotide diversity (0.004-0.008). Gene flow analysis showed high levels of connectivity among populations in the sampling areas. Analysis of molecular variance (·_ST = 0.00868, P = 0.1837), population pairwise ·_ST comparisons and genetic diflerentiation tests confrmed the lack of genetic structuring among the three localities. These analyses suggest that sampling sites analyzed can be considered as a single gene pool. Migratory behavior, the high dispersal potential of early stages and the lack of oceanographic barriers may explain its genetic homogeneity along the Peruvian sea. Historical demography was also examined. Neutrality tests, mismatch distribution and Bayesian skyline plot suggested a population expansion scenario that took place during the Late Pleistocene. This study provides novel information on population genetics of the chub mackerel in the Southeast Pacifc.