Data from: Fish population genetic structure shaped by hydroelectric power plants in the upper Rhine catchment

The Rhine catchment in Switzerland has been transformed by a chain of hydroelectric power stations. We addressed the impact of fragmentation on the genetic structure of fish populations by focusing on the European chub (Squalius cephalus). This fish species is not stocked and copes well with altered habitats, enabling an assessment of the effects of fragmentation per se. Using microsatellites, we genotyped 2133 chub from 47 sites within the catchment fragmented by 37 hydroelectric power stations, two weirs and the Rhine Falls. The shallow genetic population structure reflected drainage topology and was affected significantly by barriers to migration. The effect of power stations equipped with fishpasses on genetic differentiation was detectable, albeit weaker than that of man-made barriers without fishpasses. The Rhine Falls as the only long-standing natural obstacle (formed 14 000 to 17 000 years ago) also had a strong effect. Man-made barriers also exacerbated the upstream decrease in allelic diversity in the catchment, particularly when lacking fishpasses. Thus, existing fishpasses do have the desired effect of mitigating fragmentation, but barriers still reduce population connectivity in a fish that traverses fishpasses better than many other species. Less mobile species are likely to be affected more severely.

瑞士境内的莱茵河流域已被一系列水力发电站改造重塑。本研究以欧洲鳊（Squalius cephalus）为研究对象，探究了生境片段化对鱼类种群遗传结构的影响。该物种未经过人工增殖放流，且可较好适应改造后的生境，这使得我们能够直接评估生境片段化本身的效应。利用微卫星（microsatellites）分子标记，我们对该流域内47个采样点的2133尾欧洲鳊进行了基因分型，这些采样点所在的流域被37座水力发电站、2座堰坝以及莱茵瀑布所分割。研究显示，种群微弱的遗传分化特征既反映了流域的水文拓扑格局，同时也显著受到迁移障碍的影响。配备过鱼设施（fishpasses）的水力发电站对种群遗传分化的影响虽可被检测到，但弱于未配备过鱼设施的人工障碍。作为该流域唯一一处形成于1.4万至1.7万年前的古老天然障碍，莱茵瀑布同样对种群遗传结构产生了强烈影响。人工障碍还加剧了该流域内沿上游方向的等位基因多样性下降趋势，在未配备过鱼设施的情况下尤为显著。综上，现有的过鱼设施确实能够达到缓解生境片段化的预期效果，但对于这种比多数其他鱼类更擅长通过过鱼设施的物种而言，人工障碍仍会降低其种群间的连通性。活动能力较弱的鱼类物种则可能受到更为严重的影响。