基于线粒体COX1和ND1基因顺序的黄河上游大鼻吻鮈遗传多样性分析

Genetic diversity analysis of Rhinogobio nasutus in the upper Yellow River based on mtDNA COX 1 and ND 1 gene sequences

为探究黄河上游大鼻吻鮈(Rhinogobio nasutus)群体遗传多样性和遗传分化现状,本研究以永宁、平罗、磴口3个不同地理群体145尾大鼻吻鮈为研究对象,利用线粒体DNA COX1和ND1基因序列进行了遗传多样性分析。结果显示:COX1和ND1基因序列长度分别为1 466 bp、975 bp, A+T含量(57.25%,56.81%)均高于G+C(42.75%,43.19%)含量,具有明显的碱基组成偏向性;3个群体145尾样本中分别界定了11个和9个单倍型,均存在共享单倍型现象。在COX1和ND1基因序列中3个群体的平均单倍型多样性(Hd)、核苷酸多样性(π)及平均核苷酸差异(K)分别为0.745 3、0.001 3、1.841和0.364、0.000 48、0.472,3个群体遗传多样性呈现出磴口群体最高、平罗群体次之、永宁群体最小的特征。基于COX1和ND1的遗传变异分析(AMOVA),表明3个群体中遗传变异均主要来自群体内,且COX1基因序列中磴口群体与永宁群体之间存在显著性明显的遗传分化。基于线粒体COX1和ND1基因单倍型序列,采用邻近法(Neighbor Joining, NJ)构建系统进化树与单倍型网络结过具有一致性,表明3个群体之间无明显的谱系分化,结构比较单一,未发现形成单独分支的群体。中性检验结果显示,大鼻吻鮈进化历程符合中性进化假设,且可能存在群体扩张。因此,为了有效地保护大鼻吻鮈野生资源,建议将大鼻吻鮈从整体上进行就地保护。

Genus Rhinogobio was erected by Bleeker in 1870,and belongs to Cyprinidae,Cypriniformes,and Teleostei.A total of five species were recognized by Yue(1998),with two species of Rhinogobio distributed in the Yellow River drainage area.R.nasutus is a species restricted to China′s Yellow River drainages.However,in recent years,the number of wild populations have declined sharply.To investigate the genetic diversity and genetic differentiation of R.nasutus in the middle and upper reaches of the Yellow River,147 R.nasutus were selected from three different geographical populations,Yongning(YN),Pingluo(PL)and Dengkou(DK).Mitochondrial DNA cytochrome c oxidase subunit 1(COX 1)and NADH dehydrogenase subunit 1(ND 1)gene sequences were utilized to analyze the genetic diversity.The results showed that COX1 and ND1 gene sequences length were 1466 bp and 975 bp,respectively.A+T content(57.25%,56.81%)were more significant than G+C(42.75%,43.19%),and the base composition had apparent bias.Among 146 samples from the three populations,11 and 9 haplotypes were defined,respectively,and shared haplotypes existed in all of them.The mean haplotype diversity(H d),nucleotide diversity(π)and mean nucleotide difference(K)in COX 1 and ND 1 were 0.7453,0.0013,1.841 and 0.364,0.00048,0.472,respectively.The highest genetic diversity of the three populations was noted in the DK population,followed by the PL population and YN population.Molecular variation analysis(AMOVA)based on COX 1 and ND 1 showed that the genetic variation in the two populations mainly came from within the population,and there was significant genetic differentiation between DK and YN populations in COX 1 gene sequence.Based on the haplotype sequences of mitochondrial COX 1 and ND 1 genes obtained,the phylogenetic tree was built by Neighbor Joining(NJ)method and the structure of the haplotype network diagram was consistent.All of them showed that there was no recognizable lineage differentiation between the three populations,and the structure was relatively simple.The results of the neutral test showed that the evolutionary history of R.nasutus was consistent with the hypothesis of neutral evolution,and there might be population expansion.No group forming a separate branch was found.These results effectively fill the gap in the field of conservation genetics of R.nasutus,and grasp its population structure,genetic diversity and phylogenetic status.They also provide basis for germplasm identification and species classification and provide data support for further development of more scientific conservation strategies.Therefore,it is recommended to strengthen the protection of R.nasutus as a whole,establish effective protection measures,increase publicity and protection efforts,mainly strengthen in-situ protection,improve its habitat environment,and gradually improve the protection measures for R.nasutus,so as to effectively restore its germplasm resources.