Shine R
Zoology Department, University of Sydney, New South Wales, Australia.
Q Rev Biol. 1989 Dec;64(4):419-61. doi: 10.1086/416458.
Can sexual dimorphism evolve because of ecological differences between the sexes? Although several examples of this phenomenon are well known from studies on birds, the idea has often been dismissed as lacking general applicability. This dismissal does not stem from contradictory data so much as from the difficulties inherent in testing the hypothesis, and its apparent lack of parsimony, in comparison to the alternative explanation of sexual selection. The only unequivocal evidence for the evolution of sexual dimorphism through intersexual niche partitioning would be disproportionate dimorphism in trophic structures (e.g., mouthparts). This criterion offers a minimum estimate of the importance of ecological causes for dimorphism, because it may fail to identify most cases. A review of published literature reveals examples of sexually dimorphic trophic structures in most animal phyla. Many of these examples seem to be attributable to sexual selection, but others reflect adaptations for niche divergence between the sexes. For example, dwarf non-feeding males without functional mouthparts have evolved independently in many taxa. In other cases, males and females differ in trophic structures apparently because of differences in diets. Such divergence may often reflect specific nutritional requirements for reproduction in females, or extreme (sexually selected?) differences between males and females in habitats or body sizes. Ecological competition between the sexes may be responsible for intersexual niche divergence in some cases, but the independent evolution of foraging specializations by each sex may be of more general importance. If ecological causation for dimorphism can be demonstrated in so many cases, despite the inadequacies of the available criteria, the degree of sexual size dimorphism in many other animal species may well also have been influenced by ecological factors. Hence, it may be premature to dismiss this hypothesis, despite the difficulty of testing it.
两性异形会因为两性之间的生态差异而进化吗？尽管从对鸟类的研究中可以熟知这一现象的几个例子，但这个观点常常因缺乏普遍适用性而被摒弃。这种摒弃并非源于相互矛盾的数据，而是源于检验该假设所固有的困难，以及与性选择的另一种解释相比，它明显缺乏简约性。通过两性生态位划分实现两性异形进化的唯一明确证据是营养结构（如口器）中不成比例的两性异形。这一标准为生态因素对两性异形的重要性提供了一个最低估计，因为它可能无法识别大多数情况。对已发表文献的回顾揭示了大多数动物门类中存在两性异形营养结构的例子。这些例子中的许多似乎可归因于性选择，但其他例子则反映了两性为生态位分化而做出的适应。例如，没有功能性口器的矮小非摄食型雄性在许多分类群中独立进化。在其他情况下，雄性和雌性在营养结构上存在差异显然是由于饮食不同。这种差异通常可能反映了雌性繁殖对特定营养的需求，或者雄性和雌性在栖息地或体型上的极端（性选择的？）差异。在某些情况下，两性之间的生态竞争可能导致两性生态位分化，但两性各自觅食特化的独立进化可能具有更普遍的重要性。如果尽管现有标准存在不足，但在如此多的情况下都能证明两性异形的生态成因，那么许多其他动物物种的两性体型差异程度很可能也受到了生态因素的影响。因此，尽管难以检验这一假设，但现在就摒弃它可能为时过早。
