Tobias J A, Seddon N
Department of Zoology, Edward Grey Institute, University of Oxford, Oxford, UK.
J Evol Biol. 2009 Mar;22(3):623-36. doi: 10.1111/j.1420-9101.2008.01678.x. Epub 2009 Jan 29.
Sexual selection is thought to counteract natural selection on the grounds that secondary sexual traits are inherently costly and evolve at the expense of naturally selected traits. It is therefore commonly predicted that increased sexual selection is associated with decreased physiological tolerance or ecological plasticity. Using phylogenetic comparative methods, we test this prediction by exploring relationships between traits assumed to be sexually selected (plumage dichromatism and song structure) and traits assumed to be naturally selected (altitudinal range and habitat range) in a diverse family of tropical birds. Contrary to expectations, we find that taxa with higher levels of dichromatism, and lower song pitch, occupy a wider variety of habitats and elevations. In other words, indices of sexual selection are positively related to two standard measures of ecological generalism. One interpretation of this pattern is that sexual selection combines synergistically with natural selection, thereby increasing physiological tolerance or the propensity to adapt to novel environments. An alternative possibility is that ecological generalism increases population density, which in turn promotes sexual selection in the form of greater competition for mates. Overall, our results suggest that a synergism between natural selection and sexual selection may be widespread, but the processes underlying this pattern remain to be investigated.
性选择被认为会抵消自然选择，理由是第二性征本质上代价高昂，且是以牺牲自然选择的性状为代价而进化的。因此，人们普遍预测，性选择的增强与生理耐受性或生态可塑性的降低有关。我们运用系统发育比较方法，通过探究一个多样化的热带鸟类家族中假定为性选择的性状（羽毛两性异形和鸣叫结构）与假定为自然选择的性状（海拔范围和栖息地范围）之间的关系，来检验这一预测。与预期相反，我们发现，羽毛两性异形程度较高且鸣叫音调较低的类群，占据着更为多样的栖息地和海拔高度。换句话说，性选择指标与生态适应性的两个标准衡量指标呈正相关。对这一模式的一种解释是，性选择与自然选择协同作用，从而提高生理耐受性或适应新环境的倾向。另一种可能性是，生态适应性会增加种群密度，进而以对配偶的更大竞争形式促进性选择。总体而言，我们的结果表明，自然选择和性选择之间的协同作用可能很普遍，但这种模式背后的过程仍有待研究。
