Genetic variation and population structure of willowy flounder Tanakius kitaharai collected from Aomori, Ibaraki and Niigata in Northern Japan

Abstract

The first hypervariable region (HVR-1) of the mitochondrial DNA control region was utilized for determination of genetic variation and population structure in willowy flounder (Tanakius kitaharai) collected from Aomori, Ibaraki and Niigata. A total of 35 haplotypes were detected among 66 individuals with a total of 30 variable sites out of 387 bp sequenced. Average sequence differences between populations (1.0 - 1.1%) were comparable to those within populations (0.9 - 1.2%), suggesting no genetic heterogeneity among samples. The pattern of distribution of genetic variability with high level of haplotype diversity (h = 0.94) and moderate nucleotide diversity ( = 1.0%) was also detected in the
HVR-1 region of the mitochondrial DNA control region. AMOVA tests and the conventional population st comparisons revealed no significant genetic structure among the populations. Partitioning populations into coherent geographic groups divided willowy flounder samples (ct = -0.007, P > 0.05) into two major groups: a Sea of Japan group composed of Aomori and Niigata populations; a Pacific Ocean group composed of Ibaraki populations. The minimum spanning tree constructed with 35 haplotypes showed four low-divergent clades, corresponding to those defined in the NJ tree. However, these clades did not appear to have geographic structure. Altogether, the results indicate that willowy flounder is panmictic throughout the examined range in Aomori, Ibaraki and Niigata.