1. The presence of a dam disturbs river flow, which in turn directly affects the communities and evolutionary potential of riverine species. To detect the ecological effects of a dam on genetic diversity, genetic structure, and their progress in time, two riverine fishes living upstream and downstream of an irrigation reservoir were studied at two periods after its construction in 2004 in central Chile.
2. Samples of the Neotropical silverside Basilichthys microlepidotus and the pencil catfish Trichomycterus areolatus were obtained 2 and 7 years after the Corrales Dam was built. The microsatellite DNA variability of both species upstream and downstream of the dam was analysed.
3. Fish analysed 2 years after dam construction did not show genetic differences between upstream and downstream populations; however, fish obtained 7 years after dam construction showed differences between populations above and below the dam and differences from individuals collected 5 years earlier.
4. The current effective population sizes of both species were smaller in samples obtained upstream than in samples obtained downstream. Simulations showed a migration equal to zero as most probable after reservoir construction, suggesting that the dam is an impermeable barrier to the movement of individuals of these species. These results showed that population fragmentation in time could be related to the barrier imposed by the dam.
5. In a scenario of no new contact between populations located upstream and downstream of the dam, the simulation predicts a reduction of genetic diversity ranging from 3.98 to 8.09% over the next 60 years.
6. Analyses suggest that the Corrales Reservoir may be affecting the evolutionary potential of the populations upstream and downstream from the dam.

中文翻译：

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堰塞河：智利中部地中海气候下河流中鱼类栖息的短期和长期后果

1. 大坝的存在干扰了河流的流动，进而直接影响了河流物种的群落和进化潜力。为了检测水坝对遗传多样性，遗传结构及其及时进展的生态影响，在2004年智利中部修建了两个水库之后，研究了两个生活在灌溉水库上游和下游的河鱼。
2. 在建造Corrales大坝2年和7年后，获得了新热带银边的Basilichthys microlepidotus和铅笔cat鱼Trichomycterus areolatus的样品。分析了大坝上游和下游物种的微卫星DNA变异性。
3. 在大坝建设两年后分析的鱼没有显示上游和下游种群之间的遗传差异；但是，在水坝建设7年后获得的鱼显示出水坝上下种群之间的差异，以及5年前收集的个体之间的差异。
4. 在上游获得的样本中，两种物种的当前有效种群数量均小于下游获得的样本。模拟显示，在水库建设之后，迁移最可能为零，这表明大坝是这些物种个体运动的不可渗透的屏障。这些结果表明，人口及时分散可能与大坝施加的障碍有关。
5. 在大坝上游和下游种群之间没有新接触的情况下，模拟预测在未来60年内，遗传多样性将减少3.98％至8.09％。
6. 分析表明，科拉莱斯水库可能会影响大坝上游和下游种群的进化潜力。