Rapid morphological divergence of a stream fish in response to changes in water flow

Recent evidence indicates that evolution can occur on a contemporary time scale. However, the precise timing and patterns of phenotypic change are not well known. Reservoir construction severely alters selective regimes in aquatic habitats due to abrupt cessation of water flow. We examined the spatial and temporal patterns of evolution of a widespread North American stream fish (Pimephales vigilax) in response to stream impoundment. Gross morphological changes occurred in P. vigilax populations following dam construction in each of seven different rivers. Significant changes in body depth, head shape and fin placement were observed relative to fish populations that occupied the rivers prior to dam construction. These changes occurred over a very small number of generations and independent populations exhibited common responses to similar selective pressures. The magnitude of change was observed to be greatest in the first 15 generations post-impoundment, followed by continued but more g...

最新研究证据表明，演化可以在当代时间尺度上发生。然而，表型变化的确切时机与模式仍未得到充分阐明。由于水流突然中断，水库建设会严重改变水生栖息地的选择格局。我们针对北美广布溪流鱼类斑尾胖头鱥（Pimephales vigilax）对溪流筑坝的响应，研究了其演化的时空模式。在7条不同河流筑坝后，斑尾胖头鱥种群均出现了整体形态学变化。与筑坝前栖息于该河流的种群相比，其体高、头部形态及鳍的着生位置均发生了显著变化。这些变化仅经历了少数世代便已出现，且不同独立种群对相似选择压力展现出了一致的响应模式。研究观察到，变化幅度在筑坝后的前15个世代达到峰值，后续虽仍有持续变化，但变化速率更趋...