多基因解析长江与珠江鳤的遗传结构

Genetic structure analysis of Ochetobius elongatus between Yangtze River and Pearl River using multiple loci

为保护极濒危物种鳤(Ochetobius elongatus)的遗传多样性,通过野外调查在长江获得了7尾鳤样本,利用Sanger测序技术测定了其2个线粒体基因[细胞色素b(Cytb)和酰胺腺嘌呤二核苷酸(NADH)脱氧酶亚单位2(ND2)]和2个核基因[肌球蛋白重链6(myh6)和重组激活基因2(RAG2)]的序列,结合已公开发表的52尾珠江鳤的4个基因序列,采用系统发育分析、单倍型网状图构建、分化时间估算等方法,对珠江和长江鳤的遗传结构和分化历史展开研究。系统发育分析和单倍型网状图表明,珠江和长江鳤群体分别形成了高度分化的遗传谱系,并且在核基因水平上形成了特有的等位基因型,表明这两个水系的鳤群体独立进化且不存在基因交流。分化时间估算表明珠江和长江鳤两谱系在0.38~0.76 Ma(百万年前)分化,中更新世青藏高原的快速隆升很可能是促进其分化的重要因素。鉴于珠江和长江的鳤群体在线粒体基因和核基因层面上存在严格的地理分化,建议将这两个群体看作不同的演化显著单位(Evolutionary Significant Unit,ESU)进行区别管理和保护。

To protect the genetic diversity of a critically endangered species Ochetobius elongatus,taking seven individuals of O.elongatus collected from the field investigation in the Yangtze River as samples,we sequenced two mitochondrial genes(Cytb and ND2)and two nuclear genes(mhy6 and RAG2)for the seven samples by Sanger sequencing technique.Combining with the published four gene sequences of 52 O.elongatus samples in the Pearl River,we explored the genetic structure of O.elongatus between the Pearl River and the Yangtze River,so as to provide scientific support for its conservation.We applied phylogenetic analyses,haplotype networks and divergence time estimation.Phylogenetic analyses and haplotype networks reveal that O.elongatus populations in the two rivers generated two deep and independent lineages,and formed private alleles at the nuclear gene level.The results suggest that O.elongatus populations in the two rivers evolved independently without agene flow.The rapid lifting of the Qinghai-Xizang Plateau during the middle Pleistocene might be an important factor that triggered the split of O.elongatus populations in the two rivers 0.38~0.76 million years ago(Ma).In view of the strictly geographical division of O.elongatus populations between the two rivers at both mitochondrial and nuclear gene levels,we suggest that these two populations should be regarded as two evolutionary significant units,and targeted strategies should be urgently put forward to manage and protect its resources.