Department of Neurobiology and Behavior, Cornell University, Ithaca, NY, USA.
Proc Biol Sci. 2013 May 1;280(1761):20130482. doi: 10.1098/rspb.2013.0482. Print 2013 Jun 22.
Estimating the fitness surface of rapidly evolving secondary sexual traits can elucidate the origins of sexual isolation and thus speciation. Evidence suggests that sexual selection is highly complex in nature, often acting on multivariate sexual characters that sometimes include non-heritable components of variation, thus presenting a challenge for predicting patterns of sexual trait evolution. Laupala crickets have undergone an explosive species radiation marked by divergence in male courtship song and associated female preferences, yet patterns of sexual selection that might explain this diversification remain unknown. We used female phonotaxis trials to estimate the fitness surface for acoustic characters within one population of Laupala cerasina, a species with marked geographical variation in male song and female preferences. Results suggested significant directional sexual selection on three major song traits, while canonical rotation of the matrix of nonlinear selection coefficients (γ) revealed the presence of significant convex (stabilizing) sexual selection along combinations of characters. Analysis of song variation within and among males indicated significantly higher repeatability along the canonical axis of greatest stabilizing selection than along the axis of greatest linear selection. These results are largely consistent with patterns of song divergence that characterize speciation and suggest that different song characters have the potential to indicate distinct information to females during courtship.
估算快速进化的次要性征的适应度表面可以阐明性隔离的起源，从而揭示物种形成的过程。有证据表明，性选择在自然界中非常复杂，通常作用于多元的性特征，这些特征有时包括可遗传的变异成分，因此预测性特征进化的模式具有一定的挑战性。拉帕拉蟋蟀经历了一次爆炸式的物种辐射，其特征是雄性求偶歌曲和相关的雌性偏好发生分歧，但仍不清楚哪些性选择模式可能解释了这种多样化。我们使用雌性声诱试验来估计拉帕拉蜡蝉（Laupala cerasina）一个种群内的声学特征的适应度表面，该物种的雄性歌曲和雌性偏好存在明显的地理变异。结果表明，三个主要的歌曲特征存在显著的定向性选择，而非线性选择系数矩阵（γ）的典型旋转显示出在特征组合上存在显著的凸（稳定）性选择。对雄性内部和雄性之间的歌曲变异的分析表明，沿着最大稳定选择的典型轴的可重复性显著高于沿着最大线性选择的轴的可重复性。这些结果在很大程度上与特征分化的模式一致，表明不同的歌曲特征有可能在求偶过程中向雌性传达不同的信息。
