基于线粒体Cytb和D-Loop序列的大獭蛤5个地理群体遗传多样性研究

Analysis of genetic diversity among five populations of Lutraria Maxima based on mtDNA Cytb and D-Loop sequences

为揭示中国大獭蛤(Lutraria maxima)遗传多样性现状,基于线粒体Cytb和D-Loop序列,分析了北海、涠洲岛、湛江、厦门、福州大獭蛤5个地理群体的遗传多样性及遗传结构。结果显示:基于Cytb和D-Loop序列获得的单倍型数分别为73和27,总体单倍型多样性指数/核苷酸多样性指数分别为0.8345±0.0303/0.0023±0.0014、0.4456±0.0498/0.0014±0.0013。分子变异分析(analysis of molecular variance,AMOVA)结果显示,99.68%(Cytb)和101.16%(D-Loop)变异来自群体内,0.32%(Cytb)和-1.16%(D-Loop)变异来自群体间;遗传距离分别为0.0018~0.0029(Cytb)和0.0008~0.0020(D-Loop),群体间分化指数Fst值分别为-0.0080~0.0101(Cytb)和-0.0143^-0.0072(D-Loop),且均无显著分化(P>0.05)。中性检验Tajima’s D和Fu’s FS值均为负值(P<0.05),核苷酸不配对分布曲线呈现单峰型,这些都表明大獭蛤种群在近期经历过扩张现象,扩张时间约在更新世晚期,距今约为1.3×104~6.6×104年。上述结果表明,大獭蛤具有较高的单倍型多样性指数和较低的核苷酸多样性指数的特征,群体间无明显遗传分化,可作为一个管理保护单位。研究可为中国东、南海沿岸地区大獭蛤资源保护和持续发展与利用提供基础的参考材料。

In order to analyze the genetic diversity of Lutraria maxima in China, genetic diversity and phylogenetic relationships of L. maxima from five populations(Beihai, Weizhou Island, Zhanjiang, Fuzhou, Xiamen) were investigated based on mitochondrial cytochrome b(Cytb) and control region(D-Loop) sequences. The results showed the Cytb and D-Loop haplotypes in five populations were 73 and 27, respectively, and the haplotype diversity index and nucleotide diversity index were 0.834 5±0.030 3/0.002 3±0.001 4 and 0.445 6±0.049 8/0.001 4±0.001 3, respectively. Analysis of molecular variance(AMOVA) demonstrated that variation among population accounted for 99.68%(Cytb) and 101.16%(D-Loop) of the total variation, while the variation within populations was only 0.32%(Cytb), and-1.16%(D-Loop). The genetic distances were 0.001 8-0.002 9(Cytb) and 0.000 8-0.002 0(D-Loop), respectively. Fixation indexes Fst value among five populations were-0.008 0-0.010 1(Cytb) and-0.014 3-0.007 2(D-Loop), respectively, and there was no significant differentiation(P>0.05). Neutrality test Tajima’s D and Fu’s FS values were negative(P<0.05) and mismatch distribution curves showed a unimodal shape, indicating that L. maxima populations had experienced a population expansion possibly during the last 13 000-66 000 years. On the whole, L. maxima has a high haplotype diversity index and low nucleotide diversity index, and there is no obvious genetic differentiation among populations, which can be used as a management protection unit. These findings could be usefully applied to scientific strategies for the protection, sustainable development and commercial utilization of germplasm resources of L. maxima.