Data from: Genetic and phenotypic population divergence on a microgeographic scale in brown trout

Salmonid populations of many rivers are rapidly declining. One possible explanation is that habitat fragmentation increases genetic drift and reduces the populations’ potential to adapt to changing environmental conditions. We measured the genetic and eco-morphological diversity of brown trout (Salmo trutta) in a Swiss stream system, using multivariate statistics and Bayesian clustering. We found large genetic and phenotypic variation within only 40 km of stream length. Eighty-eight percent of all pairwise FST comparisons and 50% of the population comparisons in body shape were significant. High success rates of population assignment tests confirmed the distinctiveness of populations in both genotype and phenotype. Spatial analysis revealed that divergence increased with waterway distance, the number of weirs, and stretches of poor habitat between sampling locations, but effects of isolation-by-distance and habitat fragmentation could not be fully disentangled. Stocking intensity varied between streams but did not appear to erode genetic diversity within populations. A lack of association between phenotypic and genetic divergence points to a role of local adaptation or phenotypically plastic responses to habitat heterogeneity. Indeed, body shape could be largely explained by topographic stream slope, and variation in overall phenotype matched the flow regimes of the respective habitats.

诸多河流中的鲑科鱼类种群正快速衰退。其中一种可能的解释是，生境破碎化加剧了遗传漂变，并降低了种群适应环境变化的潜力。本研究针对瑞士某溪流水系中的褐鳟（Salmo trutta），采用多元统计与贝叶斯聚类方法，对其遗传与生态形态多样性展开了测定。研究发现，仅在40公里的溪流长度范围内，便存在显著的遗传与表型变异。所有两两FST比较中，有88%的结果具有统计学显著性；而针对体型的种群比较中，该比例为50%。种群归属检验的高成功率，证实了各种群在基因型与表型层面均存在显著分化。空间分析结果显示，种群分化程度随采样点位间的河道距离、堰坝数量以及劣质生境片段长度的增加而升高，但距离隔离与生境破碎化的影响难以完全厘清。各溪流的增殖放流强度存在差异，但似乎并未降低种群内部的遗传多样性。表型分化与遗传分化之间缺乏关联，这表明局部适应或表型可塑性响应在栖息地异质性中发挥了作用。进一步分析显示，褐鳟的体型差异可在很大程度上由溪流地形坡度解释，而整体表型变异与各栖息地的水流动态特征高度吻合。