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隔离障碍的影响，包括对杂种的选择淘汰、对迁入个体的选择淘汰以及选型交配（assortative mating）。目前仅在极少数实证研究系统中，我们才明确这些障碍在自然环境中的作用模式与相互作用机制。我们在湖栖与溪栖三棘刺鱼（Gasterosteus aculeatus, Linnaeus）的接触带开展标记-重捕实验，以评估杂种的出现情况（可用于推断生殖隔离）、杂种的年际存活率（可用于推断对杂种的选择淘汰）以及湖栖型与溪栖型特征的转变（可用于推断对迁入个体的选择淘汰）。遗传与形态学数据表明，总体上存在杂种且未出现对杂种的选择淘汰，这一结果与多项其他刺鱼相关研究的结论相悖。但我们确实观测到对更偏向湖栖型个体的选择淘汰，这表明存在从湖泊向溪流的基因流障碍。结合该研究系统此前的研究成果，我们的结果表明，多种（多数作用较弱且常呈不对称性）障碍共同作用，才对基因流形成了显著限制。本研究为湖栖-溪栖三棘刺鱼的生殖隔离障碍提供了实证依据，并强调了在自然环境中评估多种生殖隔离障碍的重要价值。