Cockburn Andrew, Osmond Helen L, Double Michael C
Evolutionary Ecology Group, School of Botany and Zoology, Australian National University, Canberra, Australian Capital Territory 0200, Australia.
Proc Biol Sci. 2008 Mar 22;275(1635):605-12. doi: 10.1098/rspb.2007.0916.
Signals used in mate attraction are predicted to be highly condition dependent, and thus should be sensitive to environmental contributions to condition. However, the effects of temporal fluctuations in the environment on sexual selection in long-lived animals have been largely ignored. Female superb fairy-wrens, Malurus cyaneus, use the time that males moult into nuptial plumage prior to the onset of the breeding season to distinguish between the extra-group sires that dominate paternity. Although moult varies predictably with age, and shows marked differences between males, the phenotypic distribution also changes radically with climate; so after dry summers few males can attempt early moult. We use the recently introduced de-lifing technique to examine sexual selection gradients over 15 years of selection. Overall, there was strong evidence of directional sexual selection for early moult. However, sexual selection was much stronger when the conditions were favourable (rainfall was high), and selection was undetectable in some years. The contribution of early moulting males to population growth increased when many males moulted early, decreased when early moulting males suffered disproportionate mortality and decreased when females lacked subordinate helpers, forcing them to cede paternity to their social partner. These data suggest that short-term and laboratory studies of mate choice and sexual selection may misrepresent or underestimate the complexity of the sexual selection landscape.
用于配偶吸引的信号预计高度依赖于个体状况，因此应该对环境对个体状况的影响敏感。然而，环境的时间波动对长寿动物的性选择的影响在很大程度上被忽视了。雌性华丽细尾鹩莺（Malurus cyaneus）利用雄性在繁殖季节开始前换羽成婚羽的时间来区分主导父权的外部群体雄性。虽然换羽随年龄有可预测的变化，并且雄性之间存在显著差异，但表型分布也会随着气候发生根本变化；所以在干燥的夏季过后，很少有雄性能够尝试提前换羽。我们使用最近引入的去除寿命影响的技术来研究15年选择过程中的性选择梯度。总体而言，有强有力的证据表明存在对提前换羽的定向性选择。然而，当条件有利（降雨量高）时，性选择要强得多，并且在某些年份中检测不到选择作用。当许多雄性提前换羽时，提前换羽的雄性对种群增长的贡献增加；当提前换羽的雄性遭受不成比例的死亡率时，以及当雌性缺乏从属帮手，迫使它们将父权让给其社会伴侣时，这种贡献会减少。这些数据表明，对配偶选择和性选择的短期和实验室研究可能会错误呈现或低估性选择格局的复杂性。
