Population demography and genetic structure of the fat greenling (Hexagrammos otakii) inferred from mtDNA control region sequence analyses

Pleistocene ice ages in addition to geographical and geological modifications have affected the natural range and habitat of marine organisms in Northwestern Pacific. The effects of glacial events have left a genomic signature, resulting in concordant phylogeographical structures among many species. To investigate the effects of Quaternary climatic changes on the evolution in H. otakii, fragments of 471 bp at the 5′ end of mitochondrial DNA control region were sequenced for 275 individuals from 10 localities in the Northern China and Japan. Both mismatch distribution analyses and neutrality tests suggested recent population expansion (64,000–227,000 years ago). Although estimated value of pairwise population differentiation (F_ST) was low, half (23 of 45) of the comparisons showed statistically significant. Coalescent-based estimates show that gene flow was asymmetric or directional, most of all comparisons (57 of 65) among populations showed low evaluation value of N_m (N_m < 10). Analysis of molecular variance (AMOVA) showed genetic structuring among groups when the data was partitioned into six groups in this study. The defined pattern of genetic variation suggested a crucial role of habitat requirement, marine current, marine gyres and history process. Absence of genetic structure over hundreds of kilometers between AO and assemblage of QD, RZ and GY might imply the common coalescent other than current gene flow. Specific exchange mechanism and fine scale genetic structure need further research using faster evolution molecular markers (microsatellite markers) and further sampling.