一项研究发现，自然选择可能限制雄性果蝇的性吸引力。Emma Hine及其同事设计了一个果蝇种群，此种群中的具有能力释放雌性果蝇最喜爱的一组信息素的雄性果蝇过多。为了进行比较，这组科研人员还建立了第二组果蝇，这组果蝇中的占据支配地位的雄性含有较少的刺激性化学素。这组作者说，第一个种群中的具有信息素吸引力的雄性数量尽管在初期多一些，在经过了7代的选择性培育之后数量稳定了下来。在之后的这个种群自然繁殖时期，这组科研人员观察到，仅仅经过了5代，人为化增强雄性吸引力的效应就下降了一半。在第二组中，不出所料，雌性与性吸引力不强的雄性交配的频率显著小于与其它雄性交配的频率。这组作者说，这些发现提示让雄性果蝇具有性吸引力的性状可能减少这种昆虫的总体适应度，并有效地将种群中具有吸引力的雄性的比例控制到一定程度。

原文出处：

PNAS  doi: 10.1073/pnas.1011876108

Natural selection stops the evolution of male attractiveness

Emma Hine1, Katrina McGuigan, and Mark W. Blows

Abstract

Sexual selection in natural populations acts on highly heritable traits and tends to be relatively strong, implicating sexual selection as a causal agent in many phenotypic radiations. Sexual selection appears to be ineffectual in promoting phenotypic divergence among contemporary natural populations, however, and there is little evidence from artificial selection experiments that sexual fitness can evolve. Here, we demonstrate that a multivariate male trait preferred by Drosophila serrata females can respond to selection and results in the maintenance of male mating success. The response to selection was associated with a gene of major effect increasing in frequency from 12 to 35% in seven generations. No further response to selection, or increase in frequency of the major gene, was observed between generations 7 and 11, indicating an evolutionary limit had been reached. Genetic analyses excluded both depletion of genetic variation and overdominance as causes of the evolutionary limit. Relaxing artificial selection resulted in the loss of 52% of the selection response after a further five generations, demonstrating that the response under artificial sexual selection was opposed by antagonistic natural selection. We conclude that male D. serrata sexually selected traits, and attractiveness to D. serrata females conferred by these traits, were held at an evolutionary limit by the lack of genetic variation that would allow an increase in sexual fitness while simultaneously maintaining nonsexual fitness. Our results suggest that sexual selection is unlikely to cause divergence among natural populations without a concomitant change in natural selection, a conclusion consistent with observational evidence from natural populations.