Department of Fish Ecology and Evolution, EAWAG Swiss Federal Institute of Aquatic Science and Technology, Center of Ecology, Evolution and Biogeochemistry, Seestrasse 79, Kastanienbaum, Switzerland.
BMC Evol Biol. 2012 Oct 27;12:210. doi: 10.1186/1471-2148-12-210.
The European trout (Salmo trutta species complex) occurs across a very wide altitudinal range from lowland rivers to alpine streams. Historically, the major European river systems contained different, evolutionarily distinct trout lineages, and some of this genetic diversity has persisted in spite of extensive human-mediated translocations. We used AFLP-based genome scans to investigate the extent of potentially adaptive divergence among major drainages and along altitudinal gradients replicated in several rivers.
The proportion of loci showing evidence of divergent selection was larger between drainages than along altitudinal transects within drainages. This suggests divergent selection is stronger between drainages, or adaptive divergence is constrained by gene flow among populations within drainages, although the latter could not be confirmed at a more local scale. Still, altitudinal divergence occurred and, at approximately 2% of the markers, parallel changes of the AFLP band frequencies with altitude were observed suggesting that altitude may well be an important source of divergent selection within rivers.
Our results indicate that adaptive genetic divergence is common both between major European river systems and along altitudinal gradients within drainages. Alpine trout appear to be a promising model system to investigate the relative roles of divergent selection and gene flow in promoting or preventing adaptation to climate gradients.
欧洲鳟鱼（鲑鱼属物种复合体）分布范围广泛，从低地河流到高山溪流，海拔跨度很大。历史上，欧洲主要的河流系统中存在着不同的、进化上不同的鳟鱼谱系，尽管经历了广泛的人为介导的迁移，但其中一些遗传多样性仍然存在。我们使用基于 AFLP 的基因组扫描来研究主要流域之间以及在几条河流中复制的海拔梯度上潜在适应性分歧的程度。
与流域内的海拔梯度相比，显示出分歧选择证据的基因座比例在流域之间更大。这表明分歧选择在流域之间更强，或者适应性分歧受到流域内种群间基因流动的限制，尽管在更局部的尺度上无法证实后者。尽管如此，仍然发生了海拔分歧，并且大约 2%的标记与海拔的 AFLP 带频率的平行变化表明，海拔很可能是河流内部分歧选择的重要来源。
我们的研究结果表明，适应性遗传分歧在欧洲主要河流系统之间以及流域内的海拔梯度上都很常见。高山鳟鱼似乎是一个很有前途的模型系统，可以研究分歧选择和基因流动在促进或阻止对气候梯度的适应方面的相对作用。
