Butlin Roger K, Saura Maria, Charrier Grégory, Jackson Benjamin, André Carl, Caballero Armando, Coyne Jerry A, Galindo Juan, Grahame John W, Hollander Johan, Kemppainen Petri, Martínez-Fernández Mónica, Panova Marina, Quesada Humberto, Johannesson Kerstin, Rolán-Alvarez Emilio
Animal and Plant Sciences, The University of Sheffield, Sheffield S10 2TN, United Kingdom; Biological and Environmental Sciences-Tjärnö, University of Gothenburg, SE-452 96, Strömstad, Sweden.
Evolution. 2014 Apr;68(4):935-49. doi: 10.1111/evo.12329. Epub 2013 Dec 23.
Parallel evolution of similar phenotypes provides strong evidence for the operation of natural selection. Where these phenotypes contribute to reproductive isolation, they further support a role for divergent, habitat-associated selection in speciation. However, the observation of pairs of divergent ecotypes currently occupying contrasting habitats in distinct geographical regions is not sufficient to infer parallel origins. Here we show striking parallel phenotypic divergence between populations of the rocky-shore gastropod, Littorina saxatilis, occupying contrasting habitats exposed to either wave action or crab predation. This divergence is associated with barriers to gene exchange but, nevertheless, genetic variation is more strongly structured by geography than by ecotype. Using approximate Bayesian analysis of sequence data and amplified fragment length polymorphism markers, we show that the ecotypes are likely to have arisen in the face of continuous gene flow and that the demographic separation of ecotypes has occurred in parallel at both regional and local scales. Parameter estimates suggest a long delay between colonization of a locality and ecotype formation, perhaps because the postglacial spread of crab populations was slower than the spread of snails. Adaptive differentiation may not be fully genetically independent despite being demographically parallel. These results provide new insight into a major model of ecologically driven speciation.
相似表型的平行进化为自然选择的作用提供了有力证据。当这些表型导致生殖隔离时，它们进一步支持了在物种形成过程中与栖息地相关的分歧选择的作用。然而，观察目前在不同地理区域占据不同栖息地的成对分歧生态型，并不足以推断其平行起源。在这里，我们展示了岩岸腹足动物滨螺（Littorina saxatilis）种群之间惊人的平行表型分歧，这些种群占据了暴露于波浪作用或螃蟹捕食的不同栖息地。这种分歧与基因交流的障碍有关，然而，遗传变异在地理上的结构化程度比在生态型上更强。使用序列数据的近似贝叶斯分析和扩增片段长度多态性标记，我们表明生态型可能是在持续基因流的情况下出现的，并且生态型的种群分离在区域和局部尺度上都是平行发生的。参数估计表明，一个地点的定殖与生态型形成之间存在很长的延迟，这可能是因为螃蟹种群的冰后期扩散比蜗牛的扩散要慢。尽管在种群统计学上是平行的，但适应性分化在基因上可能并不完全独立。这些结果为生态驱动物种形成的一个主要模型提供了新的见解。
