Mechanisms of speciation in sympatry in polymorphic crater lake cichlid fish: the Neotropical Amphilophus citrinellus species complex

最近，关于共域物种形成的理论和经验证据都表明，某些进化条件有利于共域物种形成。金龟子的物种复合体符合这些模型的几个关键特征--基于颜色的多态进行强烈的分类交配，以及基于它们咽部的多态进行营养和生态分化。这种物种复合体是物种形成过程中的一种年轻的辐射。我们计划使用微卫星标记和一段mtDNA控制区来研究尼加拉瓜三个火山口和两个大湖的Midas cichlid物种复合体的多态种群的种群遗传学。众所周知，所有种群都在地理上存在强烈的遗传分化。到目前为止，现有的证据表明，即使在火山口湖泊的完全共处条件下，遗传分离也更强烈地基于颜色，我们没有发现基于营养差异和颌骨形态之间生态位分离的显著遗传结构。因此，初步数据支持这样一种假设，即在物种形成过程中，性选择比生态分离对物种形成的贡献更大或更早。在这个项目中，我们计划增加对橘红双亲及其近缘物种的采样和生态特征，以研究平行生态系统中的分歧率(遗传和表型)和重复共处物种形成的机制。

Recently, both theoretical and empirical evidence for sympatric speciation suggested that some evolutionary conditions are conducive to speciation in sympatry. The Midas cichlid species complex (Amphilophus citrinellus) fits several of the key characteristics of these models - with strong assortative mating on the basis of a color polymorphism coupled with trophic and ecological differentiation based on a polymorphism in their pharyngeal jaws. This species complex is a young radiation in the process of speciation. We plan to use microsatellite markers and a segment of the mtDNA control region to study the population-genetics of polymorphic populations of the Midas cichlid species complex from three crater lakes and two large lakes in Nicaragua. All populations are known to be strongly genetically differentiated on the basis of geography. So far the available evidence suggests that genetic separation, even in fully sympatric conditions of the crater lakes, is more strongly based on color and we failed to find significant genetic structuring based on trophic differences and ecological niche separation between jaw morphs. Preliminary data therefore support the hypothesis that sexual selection contributes more strongly or earlier during the process of speciation than ecological separation. In this project we plan to increase the sampling and the ecological characterization of both morphs of Amphilophus citrinellus, and its closely related species, to investigate the rates of divergence (genetically and phenotypically - through morphometrics) and the mechanisms of repeated sympatric speciation in parallel ecological systems.