泉水鱼长江流域3个地理群体的遗传结构分析

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。

Genetic structure analysis of three populations of Pseudogyrincheilus procheilus in Yangtze River

Fragmentation of habitats resulting from hydropower development may lead to reproductive segregation among fish populations and adversely affect the population genetic structure of important economic and endemic local fishes. To explore the genetic effects of cascade hydropower development in the Yangtze River Basin may have on local fish populations, we analyzed genetic structure of three populations of Pseudogyrincheilus procheilus in Wujiang River, Jinsha River and Dadu River of Yangtze River using mtDNA control-region. The results showed that Wujiang River population showed highest genetic diversity among three populations, the average number of nucleotide differences index was 4.893 while nucleotide diversity index was 0.00668. Jinsha River population showed lowest genetic diversity among three populations, the average number of nucleotide differences index was 0.561 while nucleotide diversity index was 0.00077. Gene flow between Wujiang River population and Dadu River population was larger than the gene flow between Jinsha River population and two other populations. Jinsha River population and the other two groups have a far greater genetic distance. Neutrality tests and mismatch distribution analysis suggested a latest population expansion of P. procheilus. The results of this study reflected abundant genetic diversity of P. procheilus, moreover, the significant genetic differentiation between Jinsha River population and other populations might be caused by historical population expansion rather than natural selection. P. procheilus had geographically adapted populations, therefore we could predict that the impact of hydropower development on its population genetic structure will be very limited.