基于线粒体Cytb基因序列的西江流域广西境内卷口鱼遗传多样性分析

Genetic diversity analysis of Ptychidio jordani in Xijiang River flowing through Guangxi Province based on mitochondrial Cytb gene sequence

为了解西江流域广西境内卷口鱼(Ptychidio jordani)种群遗传结构及分化程度,采用线粒体Cytb基因序列对西江流域广西境内6个江段的139尾野生卷口鱼的遗传多样性进行了分析。结果显示,线粒体Cytb基因长度为1053 bp,碱基T、C、A、G的平均含量分别为29.1%、27.7%、29.3%、13.9%,其中A+T(58.4%)高于C+G(41.6%)。共定义20个单倍型,并聚为2个分支,未观察到明显的地理聚群。6个卷口鱼群体的平均单倍型多样性和平均核苷酸多样性分别为0.7682、0.0023,其中红水河群体(单倍型多样性h=0.7487,核苷酸多样性π=0.0033)遗传多样性最高,柳江群体(h=0.2744,π=0.0004)和左江群体(h=0.3747,π=0.0003)的遗传多样性相对较低。卷口鱼总体的遗传分化指数(FST)为0.4614(P<0.01),表现出较大的遗传分化。两两群体间遗传分化结果显示,左江和柳江种群之间的遗传分化程度最大,而柳江和西江之间最小。AMOVA分析表明西江流域的卷口鱼群体遗传变异一半来自群体内(53.86%),一半来自群体间(46.14%)。中性检验(Tajima's D=−1.0828,P>0.05;Fu's Fs=−6.5725,0.01<P<0.05)与碱基错配分布分析表明西江流域卷口鱼种群大约在0.07~0.187 Ma经历了种群扩张。综上,西江流域广西境内的卷口鱼柳江群体和左江群体遗传多样性较低,总群体分化程度较大,但仍属于一个种群,其中空间距离与地理阻隔对卷口鱼的遗传分化具有一定的促进作用。

In order to explore the genetic structure and differentiation degree among different Ptychidio jordani populations in Xijiang River flowing through Guangxi Province,we collected 139 individuals from six wild P.jordani populations(HSH,LIUJ,XIJ,YOUJ,YUJ,ZJ)and analyzed their genetic structure with Cytb sequences.The length of Cytb gene was 1053 bp,and the average contents of T,C,A and G were 29.1%,27.7%,29.3%and 13.9%,respectively.Besides,the A+T content(58.4%)was significantly higher than the C+G content(41.6%).A total of 20 haplotypes were defined,clustering into two branches without significant geographic clusters.The average haplotype diversity and nucleotide diversity of the six populations were 0.7682 and 0.0023,respectively.The highest genetic diversity was detected in HSH population(h=0.7487,π=0.0033),while the relatively low genetic diversity was found in LIUJ(h=0.2744,π=0.0004)and ZJ(h=0.3747,π=0.0003).The genetic differentiation index(FST)of six P.jordani populations was 0.4614(P<0.001),showing a great genetic differentiation.The degree of genetic differentiation between ZJ and LIUJ populations was the greatest,while that between LIUJ and XJ populations was the smallest.AMOVA analysis shows that part of the genetic variation was within the populations(53.86%),and part came from different populations(46.14%).Neutral test(Tajima's D=−1.0828,P>0.05;Fu's Fs=−6.5725,0.01<P<0.05)and base mismatch distribution analysis show that the P.jordani population in Xijiang River experienced population expansion 0.07−0.187 million years ago(Ma).In conclusion,the genetic diversity of P.jordani between LIUJ and ZJ populations is low in Guangxi Xijiang River;the total population differentiation degree is high,but still belongs to a population,and the spatial distance and geographical barrier can promote the genetic differentiation.