基于Cyt b基因序列的黄斑蓝子鱼群体遗传多样性分析

Genetic diversity analysis among Siganus oramin populations from coastal sea of southeast China based on mitochondrial genome Cyt b gene sequence

  • 摘要: 黄斑蓝子鱼 (Siganus oramin) 养殖群体已出现经济性状衰退和遗传多样性下降问题。为保护野生种质资源,对采自中国东南沿海7个地理群体 (湛江北部湾BB、海南文昌WC、阳江沙扒湾SB、深圳大鹏湾DP、深圳大亚湾DY、漳州东山湾DS和宁德三沙湾SS)的197尾样本进行线粒体Cyt b基因测序分析,旨在评估野生群体的遗传多样性状况。结果显示,黄斑蓝子鱼的线粒体Cyt b基因全序列长度为1 141 bp,包含140个变异位点,81个单倍型,表现出高单倍型多样性 (Hd=0.921±0.014) 和低核苷酸多样性 (Pi=0.006 4±0.001 0) 的特点。遗传距离和遗传分化结果均显示黄斑蓝子鱼群体间未发生明显分化,各地理群体亲缘关系较近。基于Cyt b基因序列构建的NJ树显示,81个单倍型散落分布在一个支系,各群体均未形成明显单系群。单倍型网络分析结果亦表明不同地理区的黄斑蓝子鱼群体间未发生明显分化。AMOVA分析表明,黄斑蓝子鱼遗传分化主要来自群体内部 (99.83%)。中性检验结果显示,Fu's Fs值为显著的负值 (−24.605, p<0.05);贝叶斯天际线图表明黄斑蓝子鱼短时间内经历了瓶颈效应以及种群扩张事件,推测其扩张时间约为1.577万年前。

     

    Abstract: The cultured populations of Siganus oramin have shown declining economic traits and reduced genetic diversity. To conserve wild germplasm resources, we analyzed mitochondrial Cyt b gene sequences from 197 specimens collected from seven geographic populations along China's southeastern coast (Beibu Gulf-Zhanjiang BB, Wenchang-Hainan WC, Shaba Bay-Yangjiang SB, Dapeng Bay-Shenzhen DP, Daya Bay-Shenzhen DY, Dongshan Bay-Zhangzhou DS, and Sansha Bay-Ningde SS),aiming to assess the genetic diversity status of wild populations.The Cyt b gene sequence was 1 141 base pairs in length, containing 140 variable sites and defining 81 haplotypes. The overall haplotype diversity was 0.921±0.014, and the nucleotide diversity was 0.006 4±0.001 0. The genetic distance and differentiation indexes showed no significant genetic differentiation among the seven populations, and both the neighbor-joining tree and haplotype network structure suggest little genetic differentiation. AMOVA analysis reveals that most variation (99.83%) was found within populations. The results of the neutral test show that the Fu's Fs value was significantly negative (−24.605, p<0.05) and the Bayesian skyline plot analysis reveals that the S. oramin population underwent a demographic bottleneck followed by a rapid population expansion over a short evolutionary time span, which suggests that S. oramin might have experienced a bottleneck effect and population expansion within a short period of time, with the estimated expansion time being about 15.77 thousand years ago.

     

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