INRA, UMR 0985 Ecology and Health of Ecosystems, 35042 Rennes, France.
Mol Ecol. 2011 Oct;20(20):4231-45. doi: 10.1111/j.1365-294X.2011.05266.x. Epub 2011 Sep 14.
Disentangling the effects of natural environmental features and anthropogenic factors on the genetic structure of endangered populations is an important challenge for conservation biology. Here, we investigated the combined influences of major environmental features and stocking with non-native fish on the genetic structure and local adaptation of Atlantic salmon (Salmo salar) populations. We used 17 microsatellite loci to genotype 975 individuals originating from 34 French rivers. Bayesian analyses revealed a hierarchical genetic structure into five geographically distinct clusters. Coastal distance, geological substrate and river length were strong predictors of population structure. Gene flow was higher among rivers with similar geologies, suggesting local adaptation to geological substrate. The effect of river length was mainly owing to one highly differentiated population that has the farthest spawning grounds off the river mouth (up to 900km) and the largest fish, suggesting local adaptation to river length. We detected high levels of admixture in stocked populations but also in neighbouring ones, implying large-scale impacts of stocking through dispersal of non-native individuals. However, we found relatively few admixed individuals suggesting a lower fitness of stocked fish and/or some reproductive isolation between wild and stocked individuals. When excluding stocked populations, genetic structure increased as did its correlation with environmental factors. This study overall indicates that geological substrate and river length are major environmental factors influencing gene flow and potential local adaptation among Atlantic salmon populations but that stocking with non-native individuals may ultimately disrupt these natural patterns of gene flow among locally adapted populations.
厘清自然环境特征和人为因素对濒危种群遗传结构的影响，是保护生物学的一个重要挑战。在这里，我们调查了主要环境特征和非本地鱼类放养对大西洋鲑（Salmo salar）种群遗传结构和局部适应的综合影响。我们使用了 17 个微卫星标记来对源自法国 34 条河流的 975 个个体进行基因分型。贝叶斯分析显示出具有五个地理上不同集群的分层遗传结构。沿海距离、地质基质和河流长度是种群结构的重要预测因子。具有相似地质的河流之间的基因流动更高，这表明了对地质基质的局部适应。河流长度的影响主要归因于一个高度分化的种群，该种群的产卵场离河口最远（可达 900 公里），而且鱼类个体最大，这表明了对河流长度的局部适应。我们在放养种群中检测到了高水平的杂交，但在邻近的种群中也检测到了，这意味着通过非本地个体的扩散，放养对这些种群产生了大规模的影响。然而，我们发现杂交个体相对较少，这表明放养鱼类的适应性较低，或者野生和放养个体之间存在一定的生殖隔离。当排除放养种群时，遗传结构增加了，与环境因素的相关性也增加了。本研究总体表明，地质基质和河流长度是影响大西洋鲑种群基因流动和潜在局部适应的主要环境因素，但非本地个体的放养可能最终会破坏这些局部适应种群之间自然的基因流动模式。
