Genetic divergence and diversity reflect a predominant freshwater resident life history in Rainbow Trout from southwestern Alaska

Rainbow Trout Oncorhynchus mykiss in southwestern Alaska occupy coastal watersheds near the northern boundary of the species native range and support a world class wild trout sport fishery. Although low freshwater temperatures and a short growing season in this region may favor anadromy, these populations appear to exhibit a freshwater resident life history strategy. In this study we used genetic data to evaluate two hypotheses regarding the influence of the presumed migratory behavior of these Rainbow Trout on reproductive isolation among and within watersheds. The results were largely consistent with the predictions but there were exceptions. The data supported the hypothesis that the freshwater resident behavior precludes marine-mediated gene flow resulting in large genetic divergence and low admixture among watersheds. The estimate of FCT (among-watershed differentiation, 0.350) was large and reflected over 96% of the variation among all sampled aggregations (FST = 0.363). However, ...栖息于阿拉斯加西南部的虹鳟（Rainbow Trout，学名Oncorhynchus mykiss）分布于该物种自然分布范围北界附近的沿海流域，支撑着世界级的野生鳟鱼休闲渔业。尽管该区域较低的淡水水温与较短的生长季可能有利于溯河洄游行为，但这些种群却呈现出淡水定居的生活史策略。本研究利用遗传数据，评估了两项关于虹鳟假定洄游行为对流域间及流域内生殖隔离影响的假说。研究结果大体与预测相符，但也存在例外情况。数据支持如下假说：淡水定居行为阻断了海洋介导的基因交流，进而导致流域间产生显著的遗传分化，且流域间的遗传混合度较低。流域间分化指数FCT（among-watershed differentiation）的估算值为0.350，该值较高，且反映了所有采样种群集群间96%以上的遗传变异（群体分化指数FST=0.363）。然而……