Full Length Research Paper

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

Yongshuang Xiao¹, Masakazu Takahashi⁴, Takashi Yanagimoto², Yan Zhang³, Tianxiang Gao¹*, Mamoru Yabe⁴ and Yasunori Sakurai⁴

¹Key Laboratory of Mariculture, Ministry of Education of China, Ocean University of China, Qingdao, 266003, China.

²National Research Institute of Far Seas Fisheries, Fukuura, Kanazawa-ku, Yokohama, 236-8648, Japan.

³Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Qingdao, 266071, China.

⁴Graduate School of Fisheries Sciences, Hokkaido University, Minato-cho, Hakodate, Hokkaido, 041-8611, Japan.

*Corresponding author. E-mail: gaozhang@ouc.edu.cn.

Abbreviation: HVR-1, The first hypervariable region; AMOVA, Analysis of molecular variance.

Accepted 3 July, 2008

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 (л = 1.0%) was also detected in the HVR-1 region of the mitochondrial DNA control region. AMOVA tests and the conventional population Φ_st comparisons revealed no significant genetic structure among the populations. Partitioning populations into coherent geographic groups divided willowy flounder samples (Φ_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.

Key words: Tanakius kitaharai, mitochondrial DNA control region, genetic variability, genetic structure.