Prevalence of disruptive selection predicts extent of species differentiation in Lake Victoria cichlids

Theory suggests that speciation with gene flow is most likely when both sexual and ecological selection are divergent or disruptive. Divergent sexual and natural selection on the visual system have been demonstrated before in sympatric, morphologically similar, sister species of Lake Victoria cichlids, but this does not explain the subtle morphological differences between them. To investigate the significance of natural selection on morphology during speciation, we here ask whether the prevalence of disruptive ecological selection differs between sympatric sister species that are at different stages of speciation. Some of our species pairs do (Pundamilia) and others do not (Neochromis) differ distinctively in sexually selected male nuptial coloration. We find that 1) evidence for disruptive selection and for evolutionary response to it, is prevalent in traits that are differentiated between sister species; 2) prevalence of both predicts the extent of genetic differentiation; 3) genetic ...

理论表明，当性选择与生态选择均呈分化或破坏性时，伴随基因流的物种形成最有可能发生。此前已有研究证实，维多利亚湖慈鲷中同域分布、形态相似的姐妹物种，其视觉系统受到分化性的性选择与自然选择，但这无法解释它们之间细微的形态差异。为探究物种形成过程中自然选择对形态性状的重要性，本研究旨在明确：处于物种形成不同阶段的同域姐妹物种间，破坏性生态选择的普遍性是否存在差异。我们选取的部分物种对（如Pundamilia属）在性选择相关的雄性婚色上存在显著差异，而另一些物种对（如Neochromis属）则无此明显分化。研究发现：1）在姐妹物种间已分化的性状中，破坏性选择及其进化响应的证据普遍存在；2）二者的普遍性可预测遗传分化程度；3）遗传...