Kappeler Peter M
Department of Zoology, Duke University, Durham, North Carolina.
Am J Primatol. 1990;21(3):201-214. doi: 10.1002/ajp.1350210304.
The four major hypotheses advanced to explain the evolution of sexually dimorphic characters invoke sexual selection, natural selection, allometry, and phylogenetic inertia. In this paper, each of these hypotheses is examined for its usefulness in explaining the inter-specific variation in sexual size dimorphism among prosimian primates. Data on body weight and the degree of sexual dimorphism were obtained for 32 prosimian and 95 simian species. Although prosimians exhibited significantly less sexual dimorphism than simians, there was nevertheless significant variation in dimorphism among them. The degree of sexual dimorphism in prosimians did not show significant variance at any taxonomic level, but the majority of variance occurred within genera. Thus, sexual dimorphism in size among prosimians is probably not constrained by phylogeny at the generic level and above. There was no significant correlation between body size and the degree of sexual dimorphism in prosimians, suggesting the absence of an allometric effect. Similarly there was no relationship between body size and sexual dimorphism among simians in this size range. This result suggested that the expression of sexual dimorphism may nevertheless be influenced by absolute size. In prosimians, inter-specific differences in sexual dimorphism were not correlated with variance in male reproductive success. It is suggested that speed and agility of males, rather than size and strength, might have been favored by intra-sexual selection in most prosimians. It seems also plausible that the relative monomorphism of most prosimians, especially in the Lemuriformes, might be a result of increased female size favored by natural selection. Consideration of all natural and sexual selective pressures that affect size in both sexes separately is required to understand the adaptive function and evolution of primate size dimorphism.
为解释两性异形特征的进化而提出的四个主要假说是性选择、自然选择、异速生长和系统发育惯性。在本文中，对这些假说中的每一个在解释原猴亚目灵长类动物两性大小异形的种间变异方面的实用性进行了检验。获取了32种原猴亚目动物和95种猴亚目动物的体重及两性异形程度的数据。尽管原猴亚目动物表现出的两性异形比猴亚目动物明显要少，但它们之间的异形程度仍存在显著差异。原猴亚目动物的两性异形程度在任何分类水平上都没有表现出显著差异，但大多数差异发生在属内。因此，原猴亚目动物在属及以上分类水平上的大小两性异形可能不受系统发育的限制。原猴亚目动物的体型与两性异形程度之间没有显著相关性，这表明不存在异速生长效应。同样，在这个体型范围内，猴亚目动物的体型与两性异形之间也没有关系。这一结果表明，两性异形的表现可能仍然受到绝对体型的影响。在原猴亚目动物中，两性异形的种间差异与雄性繁殖成功率的差异没有相关性。有人认为，在大多数原猴亚目动物中，雄性的速度和敏捷性，而非体型和力量，可能受到了同性选择的青睐。大多数原猴亚目动物，尤其是狐猴科动物相对单一的两性形态，可能是自然选择有利于雌性体型增大的结果。要理解灵长类动物大小异形的适应功能和进化，需要分别考虑影响两性体型的所有自然选择和性选择压力。
