泉水鱼长江流域3个地理群体的遗传结构分析

Genetic Structure Analysis of Three Pseudogyrincheilus procheilus Populations in the Yangtze River Basin

水电开发造成的栖息地片段化可能导致鱼类群体间出现生殖隔离,对流域内重要经济和特有鱼类的群体遗传结构产生不利影响。为探究长江流域梯级水电开发可能对泉水鱼（Pseudogyrincheilus procheilus）群体产生的遗传影响,利用线粒体控制区对泉水鱼长江流域的乌江、金沙江、大渡河3个地理群体的遗传结构进行了分析。结果表明,乌江群体的遗传多样性最高,平均核苷酸差异（k）和核苷酸多样性指数（Pi）分别为4.893和0.00668;金沙江群体遗传多样性最小,k和Pi值分别为0.561和0.00077,大渡河群体遗传多样性与乌江群体相近。泉水鱼3个地理群体之间有显著的遗传分化。乌江群体和大渡河群体间的基因流大于金沙江群体和其他2个群体间的基因流,金沙江群体和其他2个群体间有着较远的遗传距离。Fu＇s Fs检验结果显示,3个地理群体的Fs值均为负值,核苷酸不配对分布均呈现明显的单峰型,揭示了各个泉水鱼群体均经历了明显的群体扩张。研究结果反映出泉水鱼遗传多样性较为丰富,金沙江群体和其他群体间显著的遗传差异可能是由于历史扩张而非自然选择造成的,泉水鱼存在区域化适应的地理群体,可预见梯级水电开发对其遗传结构的影响将十分有限。

Habitat fragmentation resulting from hydropower development isolates fish populations,adversely affecting their genetic structure. Pseudogyrincheilus procheilus is a peculiar cyprinid,the only species in its genus,and an important economic fish in China. The fish widely inhabits the main stem and tributaries of the Yangtze River above Yichang and the Wujiang River. To explore the potential genetic effects of cascade hydropower development on local fish populations in the Yangtze River basin,we analyzed the genetic structure of three P. procheilus populations in the Wujiang,Jinsha and Dadu Rivers using the mt DNA control-region. P. procheilus specimens from the three populations were collected from the Wujiang River,the Panzhihua section of Jinsha River and the Leshan section of Dadu River in 2009. Twenty-three individuals of different body length,body weight and ages were collected from each population. Among the three populations,the Wujiang River population displayed the highest genetic diversity,with an average of 4. 893 nucleotide differences and a mean nucleotide diversity index of 0. 00668. The Jinsha River population presented the lowest genetic diversity,with an average of 0. 561 nucleotide differences and a nucleotide diversity index of 0. 00077. The genetic diversity of Dadu River population was similar to that of the Wujiang River. Gene flow between Wujiang River and Dadu River populations was larger than that between the Jinsha River and the other two populations,indicating a larger genetic difference in the Jinsha River population. The neighbor-joining phylogenetic tree of the three P. prochilus populations shows that the individuals of Jinsha River cluster into one group,while the individuals of Wujiang River and Dadu River mutually clustered and crossed,also indicating a large genetic distance between the Jinsha River population and the other two. The Tajima D-test,Fu Ftest and mismatch distribution analysis clearly shows an expansion of all three P. procheilus populations and high genetic diversity in the P. procheilus populations of the Yangtze River basin. The significant genetic difference between the Jinsha River population and other two populations could result from historical expansion rather than natural selection. Because P. procheilus displays a geographically adapted population,we predict that the impact of hydropower development on the genetic structure of the species will be limited.