基于线粒体Cyt b基因的龙头鱼群体遗传结构分析

在我国黄海、东海和南海海岸带上, 选取青岛、南通、舟山、三门、宁德、泉州和湛江共7个群体164尾龙头鱼(Harpadon nehereus)为研究对象, 通过PCR扩增共获得长度为1112 bp的线粒体DNA细胞色素b (Cyt b)基因序列, 共检测到32个变异位点, 其中单变异位点27个, 简约信息位点1个。164条序列定义了29个单倍型, 平均单倍型多样性(H_d)和核苷酸多样性(π)分别为0.3026±0.0479和0.000371±0.000379, 其中泉州群体的单倍型多样性和核苷酸多样性均最低。分析比较了不同龙头鱼群体间遗传变异情况, 发现群体间平均遗传距离为0.00035, 遗传分化指数F_ST值均小于0.05, 群体间没有发生明显的遗传分化。AMOVA分析结果显示龙头鱼群体遗传差异主要来源于群体内个体间的变异。中性检验的Tajima’s D和Fu’s F_s统计值均为负值且显著偏离中性, 核苷酸不配对分布图呈现明显的单峰分布, 表明龙头鱼历史上经历了群体扩张事件, 参考已知海洋鱼类Cyt b基因2%每百万年的进化速率, 估算群体扩张发生的时间大约在0.08—0.32百万年前的第四纪更新世中晚期。

THE GENETIC STRUCTURE OF THE BOMBAY DUCK (HARPADON NEHEREUS) BASED ON MITOCHONDRIAL CYT B GENE

To explore genetic structure of 164 Bombay duck (Harpadon nehereus), fishes from Qingdao, Nantong, Zhoushan, Sanmen, Ningde, Quanzhou and Zhanjiang in the coastal areas of the Yellow Sea, East China Sea and South China Sea were collected to sequence the mitochondrial DNA cytochrome b (Cyt b) gene fragment. Thirty-two mutation sites, including 27 single mutation sites and 1 simple mutation site were detected. The 164 sequences defined a total of 29 haplotypes. The average haplotype diversity (H_d) and nucleotide diversity (π) were (0.3026±0.0479) and (0.000371±0.000379), respectively, and both the lowest haplotype diversity and the lowest nucleotide diversity were Quanzhou population. The average genetic distance among different populations was 0.00035 and the genetic differentiation index F_ST value was less than 0.05, indicating no obvious genetic differentiation among the populations. The re-sults of AMOVA showed that the genetic difference of Bombay duck populations was mainly from the variation among individuals within the population. The values of Tajima’s D and Fu’s F_s tests were both negatively and significantly deviated from neutral test. The nucleotide mismatch distribution showed distinct unimodal, indicating that Bombay duck experienced a population expansion event in history. We estimated that the population expansion occurred about 0.08—0.32 million years ago in the middle and late Quaternary Pleistocene based on the evolutionary rate of Cyt b gene 2%/Ma (millions years) in marine fishes.