Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada.
Am Nat. 2010 Apr;175(4):401-14. doi: 10.1086/650719.
A widely held view is that the strength and form of natural selection varies in time and space in response to varying ecological forces; however, adequate quantitative evaluations of this are relatively scarce. In this study, we measured the strength and form of sexual selection acting on a suite of male morphological traits in a wild ambush bug (Phymata americana) population at 10 sampling dates over 2 years. We tested the prediction that the strength and direction of sexual selection would be associated with one or more important ecological variables. We found that patterns of multivariate selection varied considerably over time, and even within a season. Yet, for this population, a sexually dimorphic color pattern trait was consistently a target of directional selection. The strength of sexual selection on this trait was related to both sex ratio and density, which is consistent with the idea that ecological factors can play an important role in generating patterns of sexual selection. We also demonstrate that the median strength of linear selection obtained from replicated cross-sectional methods was qualitatively similar to the estimates obtained from longitudinal methods, providing multiple lines of evidence that the evolution of sexual color dimorphism in this species is attributable to sexual selection.
一种普遍的观点认为，自然选择的强度和形式会随时间和空间的变化而变化，以适应不断变化的生态力量；然而，对此进行充分的定量评估相对较少。在这项研究中，我们在两年内的 10 个采样日期测量了一套雄性形态特征在野外伏击虫（Phymata americana）种群中所受到的性选择的强度和形式。我们检验了这样一个预测，即性选择的强度和方向将与一个或多个重要的生态变量相关。我们发现，多变量选择的模式在时间上有很大的变化，甚至在一个季节内也是如此。然而，对于这个种群来说，一种性二态的颜色模式特征一直是定向选择的目标。这个特征的性选择强度与性别比例和密度有关，这与生态因素在产生性选择模式方面发挥重要作用的观点是一致的。我们还证明，从重复的横截面方法中获得的线性选择的中位数强度与从纵向方法中获得的估计值在定性上是相似的，这提供了多条证据表明，该物种的性色彩二态性的进化归因于性选择。
