Data from: Genetic differentiation and selection against migrants in evolutionarily replicated extreme environments

We investigated mechanisms of reproductive isolation in livebearing fishes (genus Poecilia) inhabiting sulfidic and nonsulfidic habitats in three replicate river drainages. Although sulfide spring fish convergently evolved divergent phenotypes, it was unclear if mechanisms of reproductive isolation also evolved convergently. Using microsatellites, we found strongly reduced gene flow between adjacent populations from different habitat types, suggesting that local adaptation to sulfidic habitats repeatedly caused the emergence of reproductive isolation. Reciprocal translocation experiments indicate strong selection against immigrants into sulfidic waters, but also variation among drainages in the strength of selection against immigrants into nonsulfidic waters. Mate choice experiments revealed the evolution of assortative mating preferences in females from nonsulfidic but not from sulfidic habitats. The inferred strength of sexual selection against immigrants (RIs) was negatively correlated with the strength of natural selection (RIm), a pattern that could be attributed to reinforcement, whereby natural selection strengthens behavioral isolation due to reduced hybrid fitness. Overall, reproductive isolation and genetic differentiation appear to be replicated and direct consequences of local adaptation to sulfide spring environments, but the relative contributions of different mechanisms of reproductive isolation vary across these evolutionarily independent replicates, highlighting both convergent and nonconvergent evolutionary trajectories of populations in each drainage.

我们针对栖息于三个独立重复河流流域内硫化物生境（sulfidic habitats）与非硫化物生境（nonsulfidic habitats）中的胎生鱼类（livebearing fishes）花鳉属（Poecilia）的生殖隔离（reproductive isolation）机制展开了研究。尽管硫化泉鱼类已趋同演化出差异化表型，但生殖隔离机制是否同样发生了趋同演化仍尚不明确。借助微卫星标记（microsatellites）分析，我们发现不同生境类型的相邻种群间基因流（gene flow）显著降低，这表明对硫化物生境的局部适应反复推动了生殖隔离的形成。互易移植实验（reciprocal translocation experiments）结果显示，外来个体进入硫化水环境会受到强烈的选择压，而不同流域中，外来个体进入非硫化水环境的选择压强度存在差异。配偶选择实验表明，非硫化物生境的雌性个体演化出了选型交配偏好（assortative mating preferences），而硫化物生境的雌性个体则未出现该偏好。我们推断，针对外来个体的性选择（sexual selection）强度（RIs）与自然选择（natural selection）强度（RIm）呈负相关，这一模式可归因于强化选择（reinforcement）：即当杂交适合度（hybrid fitness）降低时，自然选择会强化行为隔离。总体而言，生殖隔离与遗传分化（genetic differentiation）似乎是对硫化泉生境局部适应的可重复直接结果，但不同生殖隔离机制的相对贡献在这些演化独立的重复种群中存在差异，这凸显了各流域内种群演化轨迹兼具趋同性与非趋同性的特征。