Dionne Mélanie, Caron François, Dodson Julian J, Bernatchez Louis
Département de Biologie, Université Laval, Québec, Canada G1V 0A6.
Mol Ecol. 2008 May;17(10):2382-96. doi: 10.1111/j.1365-294X.2008.03771.x. Epub 2008 Apr 21.
Disentangling evolutionary forces that may interact to determine the patterns of genetic differentiation within and among wild populations is a major challenge in evolutionary biology. The objective of this study was to assess the genetic structure and the potential influence of several ecological variables on the extent of genetic differentiation at multiple spatial scales in a widely distributed species, the Atlantic salmon, Salmo salar. A total of 2775 anadromous fish were sampled from 51 rivers along the North American Atlantic coast and were genotyped using 13 microsatellites. A Bayesian analysis clustered these populations into seven genetically and geographically distinct groups, characterized by different environmental and ecological factors, mainly temperature. These groups were also characterized by different extent of genetic differentiation among populations. Dispersal was relatively high and of the same magnitude within compared to among regional groups, which contrasted with the maintenance of a regional genetic structure. However, genetic differentiation was lower among populations exchanging similar rates of local as opposed to inter-regional migrants, over the same geographical scale. This raised the hypothesis that gene flow could be constrained by local adaptation at the regional scale. Both coastal distance and temperature regime were found to influence the observed genetic structure according to landscape genetic analyses. The influence of other factors such as latitude, river length and altitude, migration tactic, and stocking was not significant at any spatial scale. Overall, these results suggested that the interaction between gene flow and thermal regime adaptation mainly explained the hierarchical genetic structure observed among Atlantic salmon populations.
厘清可能相互作用以决定野生种群内部和种群间遗传分化模式的进化力量，是进化生物学中的一项重大挑战。本研究的目的是评估广泛分布的物种大西洋鲑（Salmo salar）在多个空间尺度上的遗传结构，以及若干生态变量对遗传分化程度的潜在影响。从北美大西洋沿岸的51条河流中总共采集了2775条溯河产卵鱼类样本，并使用13个微卫星进行基因分型。贝叶斯分析将这些种群聚类为七个遗传和地理上不同的群体，这些群体具有不同的环境和生态因素，主要是温度。这些群体在种群间的遗传分化程度也有所不同。与区域群体之间相比，区域内部的扩散相对较高且幅度相同，这与区域遗传结构的维持形成对比。然而，在相同地理尺度上，交换相似本地迁移率而非区域间迁移率的种群之间的遗传分化较低。这就提出了一个假设，即基因流可能受到区域尺度上局部适应的限制。根据景观遗传学分析，发现沿海距离和温度状况都会影响观察到的遗传结构。在任何空间尺度上，纬度、河流长度、海拔、洄游策略和放流等其他因素的影响都不显著。总体而言，这些结果表明，基因流与热状况适应之间的相互作用主要解释了在大西洋鲑种群中观察到的层次遗传结构。
