基于线粒体Cytb基因序列的褐石斑鱼种群遗传多样性分析

Genetic Diversity Analysis of Epinephelus bruneus Grouper Populations Based on Mitochondrial Cytb Gene Sequences

为评估种质资源状况被世界自然保护联盟(International Union for Conservation of Nature, IUCN)评定为易危物种的褐石斑鱼(Epinephelus bruneus)野生种群的遗传多样性和遗传分化水平,采用PCR方法测定褐石斑鱼西太平洋海区的中国海南岛(HN)、福建厦门(XM)和韩国济州岛(HG)3个地理群体的线粒体细胞色素b(Cytb)基因的部分序列,并对其基因序列遗传变异、谱系结构和群体扩张历史特征进行分析。结果显示,褐石斑鱼3个地理种群(88个个体)共检测出18个多态位点,共有7种单倍型;各地理群体遗传多样性水平较低,而且单倍型在群体间分布不均,韩国群体遗传多样性最高,中国海南和厦门群体遗传多样性较低。地理距离最远的韩国群体和中国海南群体遗传分化最高(F_(ST)=0.177 5),地理距离最近的中国海南群体和厦门群体的遗传分化最低(F_(ST)=0.013 4)。Mantel检验结果显示,3个褐石斑鱼群体间遗传距离和地理距离间存在显著相关,距离隔离(Isolation by Distance, IBD)是褐石斑鱼群体遗传分化的主要因素。褐石斑鱼群体遗传变异主要来源于群体内,群体间存在中度遗传分化(F_(ST)=0.097 1)。褐石斑鱼Cytb基因单倍型网络图表现为简单星形结构,符合群体扩张的历史特征。Tajima′s D和Fu′s Fs中性检验结果也证实西太平洋海区褐石斑鱼群体存在扩张的历史特征。本研究结果表明,西太平洋海区的褐石斑鱼总体遗传多样性水平较低,野生种质资源极易受到渔业捕捞和气候变化的影响而衰退,在全球气候变化的背景下,急需加强其种质资源的保护工作。

In order to evaluate the genetic diversity and genetic differentiation level of the wild population of Epinephelus bruneus,which was assessed as a vulnerable species by the International Union for Conservation of Nature(IUCN),the partial sequences of mitochondrial Cytochrome b(Cytb)gene in three geographical populations of Hainan Island(HN),Xiamen(XM),China and Jeju Island(HG)in the western Pacific Ocean were determined by Polymerase Chain Reaction(PCR)technique.The genetic variation,phylogenetic structure and population expansion history of the gene sequence were analyzed.The results showed that a total of 18 polymorphic loci and 7 haplotypes were detected in 3 geographical populations(88 individuals)of E.fuscoguttatus.The genetic diversity level of each geographical population in China was low,and the haplotypes were unevenly distributed among the populations.The genetic diversity of the Korean population was the highest,and the genetic diversity of the Hainan and Xiamen populations was lower.The genetic differentiation of the Korean population and the Hainan population in China with the farthest geographical distance was the highest(F ST=0.1775),and the genetic differentiation of the Hainan population and the Xiamen population with the closest geographical distance was the lowest(F ST=0.0134).The results of Mantel test showed that there was a significant correlation between genetic distance and geographical distance among the three populations,and Isolation by Distance(IBD)was the main factor for the genetic differentiation of E.bruneus grouper populations.The genetic variation of E.bruneus grouper population was mainly derived from within the population,and there was moderate genetic differentiation among the populations(F ST=0.0971).The haplotype network of Cytb gene of E.bruneus showed a simple star structure,which was consistent with the historical characteristics of population expansion.The results of Tajima′s D and Fu′s Fs neutrality tests also confirmed the historical expansion of the E.bruneus population in the Western Pacific Ocean.The results of this study show that the overall genetic diversity level of E.bruneus in the Western Pacific Ocean is low,and the wild germplasm resources are highly vulnerable to the impact of fishing and climate change.Under the background of global climate change,it is urgent to strengthen the protection of germplasm resources.