Data from: Assessing reproductive isolation using a contact zone between parapatric lake-stream stickleback ecotypes

Ecological speciation occurs when populations evolve reproductive isolation as a result of divergent natural selection. This isolation can be influenced by many potential reproductive barriers, including selection against hybrids, selection against migrants, and assortative mating. How and when these barriers act and interact in nature is understood for relatively few empirical systems. We used a mark-recapture experiment in a contact zone between lake and stream three-spined sticklebacks (Gasterosteus aculeatus, Linnaeus) to evaluate the occurrence of hybrids (allowing inferences about reproductive isolation), the inter-annual survival of hybrids (allowing inferences about selection against hybrids), and the shift in lake-like versus stream-like characteristics (allowing inferences about selection against migrants). Genetic and morphological data suggest the occurrence of hybrids and no selection against hybrids in general, a result contradictory to a number of other studies of sticklebacks. However, we did find selection against more lake-like individuals, suggesting a barrier to gene flow from the lake into the stream. Combined with previous work on this system, our results suggest that multiple (most weakly and often asymmetric) barriers must be combining to yield substantial restrictions on gene flow. This work provides evidence of a reproductive barrier in lake-stream sticklebacks and highlights the value of assessing multiple reproductive barriers in natural contexts.

生态物种形成（Ecological speciation）指种群因趋异自然选择演化出生殖隔离的过程。此类生殖隔离可受多种潜在生殖屏障的影响，包括杂交个体选择淘汰、迁入个体选择淘汰以及选型交配（assortative mating）。目前仅在极少数实证研究体系中，我们才明确这些屏障在自然环境中如何发挥作用并相互影响。
我们在湖溪三刺鱼（Gasterosteus aculeatus Linnaeus）的接触带开展标记-重捕实验，以评估杂交个体的存在情况（可用于推断生殖隔离）、杂交个体的年际存活率（可用于推断杂交个体选择淘汰的强度）以及类湖型与类溪型特征的转变（可用于推断迁入个体选择淘汰的强度）。
遗传与形态学数据显示，总体存在杂交个体且未出现普遍的杂交个体选择淘汰现象，这一结果与多项针对三刺鱼的其他研究结论相悖。
但我们确实发现了对类湖型个体的选择淘汰，这表明存在从湖泊向溪流的基因流屏障。
结合该研究体系此前的研究成果，我们的结果表明，多种（多数作用较弱且常呈不对称性）生殖屏障共同作用，才对基因流形成了显著限制。
本研究为湖溪三刺鱼种群中存在生殖屏障提供了直接证据，并强调了在自然环境中评估多种生殖屏障的重要学术价值。