梯级水利工程背景下的嘉陵江干流蛇鮈群体遗传多样性和遗传结构

Genetic diversity and population structure of Saurogobio dabryi under cascade water conservancy projects in the Jialing River

随着嘉陵江航道渠化工程建设逐步完成,由此造成的嘉陵江水生生境破碎化、鱼类资源衰退等问题日益凸显。在这种情形下,鱼类的遗传多样性是否受到影响,是非常令人关心的问题。2018年7–12月于嘉陵江干流朝天区(CT)、苍溪县(CX)、蓬安县(PA)、合川区(HC)4个区域采集蛇鮈(Saurogobio dabryi)样本113尾,以线粒体控制区序列和微卫星位点为分子标记,研究梯级水利工程背景下蛇鮈种群的遗传多样性与遗传结构。结果显示:在遗传多样性分析中,无论是线粒体数据还是微卫星标记,下游江段HC种群的遗传多样性参数(PIC=0.543,π=0.0264,Hd=0.940)均显著高于中上游江段CT、CX和PA种群,推测这种现象可能与HC种群地处于长江干流交汇口有关;相反处于上游江段的CT种群的遗传多样性和单倍型数量均较高,推测可能与近期种群扩张有关;在种群结构分析中,CT、CX和PA处于同一分支,HC种群成为独立一支,单倍型网络图和系统发育分析显示同样结果,推测与水利工程导致的地理隔离与开闸放水形成向下的基因流向有关。

Aims:In recent years,with nearing the completion of channelization project of the Jialing River,the fragmentation of aquatic habitats,the decline of fish resources and other issues caused by the dams are becoming increasingly acute.Under the circumstances,it has been a worrying problem that whether the fish genetic diversity has been affected.The aim of this study is to analyze the genetic diversity and genetic structure of Saurogobio dabryi population under the background of cascade water conservancy project in the Jialing River by using mitochondrial control region sequence and microsatellite loci as molecular markers.Methods:From July to December in 2018,113 tails of S.dabryi were collected from Jialing River where the sampled sites were Chaotian District(CT),Cangxi County(CX),Peng’an County(PA)and Hechuan District(HC),respectively.The genetic diversity and genetic structure of S.dabryi population under the background of cascade water conservancy project were studied by using the mtDNA control region sequences and 10 microsatellite loci.Results:The results showed that in genetic diversity analysis,whether mitochondria data or microsatellite marker,the genetic diversity parameters of HC population(PIC=0.543,π=0.0264,Hd=0.940)were significantly higher than upstream and midstream(CT,CX and PA)populations.It was speculated that this phenomenon may be associated with HC population was located in the Yangtze river mainstream intersection.On the contrary,the genetic diversity and haploid number of CT population was higher,which may be associated with the population expansion in CT population,recently.In the analysis of population structure,CT,CX and PA populations were in the same branch and HC population in an independent branch.Haplotype network diagram and phylogenetic analysis showed the same result,which might be related to the geographical isolation caused by water conservancy projects and the formation of downward gene flow caused by water release.Conclusion:The research results not only reveal the genetic diversity characteristics,population structure and population dynamics of S.dabryi population in each section of Jialing River under the background of cascade water conservancy project development,but also provide basic data for the genetic research of small and medium-sized fish in Jialing River in the future.By comparing the results of this study with the morphological differences,it was verified that there were also significant genetic differences in the population of S.dabryi in each section of Jialing River under the condition of significant differences in external morphology,so the phenomenon indicates that the natural geographical differences and genetic differences shaped the genetic pattern of species together.