Arnegard Matthew E, Kondrashov Alexey S
Department of Neurobiology and Behavior, Cornell University, Ithaca, New York 14853, USA.
Evolution. 2004 Feb;58(2):222-37.
According to Darwin, sympatric speciation is driven by disruptive, frequency-dependent natural selection caused by competition for diverse resources. Recently, several authors have argued that disruptive sexual selection can also cause sympatric speciation. Here, we use hypergeometric phenotypic and individual-based genotypic models to explore sympatric speciation by sexual selection under a broad range of conditions. If variabilities of preference and display traits are each caused by more than one or two polymorphic loci, sympatric speciation requires rather strong sexual selection when females exert preferences for extreme male phenotypes. Under this kind of mate choice, speciation can occur only if initial distributions of preference and display are close to symmetric. Otherwise, the population rapidly loses variability. Thus, unless allele replacements at very few loci are enough for reproductive isolation, female preferences for extreme male displays are unlikely to drive sympatric speciation. By contrast, similarity-based female preferences that do not cause sexual selection are less destabilizing to the maintenance of genetic variability and may result in sympatric speciation across a broader range of initial conditions. Certain groups of African cichlids have served as the exclusive motivation for the hypothesis of sympatric speciation by sexual selection. Mate choice in these fishes appears to be driven by female preferences for extreme male phenotypes rather than similarity-based preferences, and the evolution of premating reproductive isolation commonly involves at least several genes. Therefore, differences in female preferences and male display in cichlids and other species of sympatric origin are more likely to have evolved as isolating mechanisms under disruptive natural selection.
根据达尔文的观点，同域物种形成是由对多种资源的竞争所导致的分裂性、频率依赖型自然选择驱动的。最近，一些作者认为分裂性性选择也能导致同域物种形成。在此，我们使用超几何表型模型和基于个体的基因型模型，在广泛的条件下探究性选择导致的同域物种形成。如果偏好性状和展示性状的变异性均由不止一两个多态位点引起，那么当雌性偏好极端雄性表型时，同域物种形成需要相当强烈的性选择。在这种配偶选择方式下，只有当偏好和展示的初始分布接近对称时，物种形成才会发生。否则，种群会迅速丧失变异性。因此，除非极少数位点的等位基因替换足以实现生殖隔离，否则雌性对极端雄性展示的偏好不太可能驱动同域物种形成。相比之下，不会导致性选择的基于相似性的雌性偏好对遗传变异性的维持造成的破坏较小，并且可能在更广泛的初始条件下导致同域物种形成。某些非洲丽鱼科鱼类群体一直是性选择导致同域物种形成这一假说的唯一推动因素。这些鱼类的配偶选择似乎是由雌性对极端雄性表型的偏好而非基于相似性的偏好驱动的，并且交配前生殖隔离的进化通常涉及至少几个基因。因此，丽鱼科鱼类及其他同域起源物种中雌性偏好和雄性展示的差异更有可能是在分裂性自然选择下作为隔离机制进化而来的。
