Data from: Evolutionary optimum for male sexual traits characterized using the multivariate Robertson–Price Identity

Phenotypes tend to remain relatively constant in natural populations, suggesting a limit to trait evolution. Although stationary phenotypes suggest stabilizing selection, directional selection is more commonly reported. However, selection on phenotypes will have no evolutionary consequence if the traits do not genetically covary with fitness, a covariance known as the Robertson–Price Identity. The nature of this genetic covariance determines if phenotypes will evolve directionally or whether they reside at an evolutionary optimum. Here, we show how a set of traits can be shown to be under net stabilizing selection through an application of the multivariate Robertson–Price Identity. We characterize how a suite of male sexual displays genetically covaries with fitness in a population of Drosophila serrata. Despite strong directional sexual selection on these phenotypes directly and significant genetic variance in them, little genetic covariance was detected with overall fitness. Instead, genetic analysis of trait deviations showed substantial stabilizing selection on the genetic variance of these traits with respect to overall fitness, indicating that they reside at an evolutionary optimum. In the presence of widespread pleiotropy, stabilizing selection on focal traits will arise through the net effects of selection on other, often unmeasured, traits and will tend to be stronger on trait combinations than single traits. Such selection may be difficult to detect in phenotypic analyses if the environmental covariance between the traits and fitness obscures the underlying genetic associations. The genetic analysis of trait deviations provides a way of detecting the missing stabilizing selection inferred by recent metaanalyses.

表型（phenotype）在自然种群中往往保持相对恒定，这表明性状进化存在一定限制。尽管稳定表型提示存在稳定选择（stabilizing selection），但定向选择（directional selection）的相关报道更为常见。然而，若性状与适合度（fitness）不存在遗传协方差，则对表型的选择不会产生进化效应，这种协方差被称为罗伯逊-普莱斯恒等式（Robertson–Price Identity）。该遗传协方差的本质决定了表型是会发生定向进化，还是会停留在进化最优值处。本研究展示了如何通过应用多变量罗伯逊-普莱斯恒等式（multivariate Robertson–Price Identity），证实一组性状处于净稳定选择作用之下。我们对斑翅果蝇（Drosophila serrata）种群中一系列雄性性展示（male sexual displays）性状与适合度的遗传协方差进行了表征。尽管这些表型直接受到强烈的定向性选择作用，且自身存在显著的遗传方差（genetic variance），但未检测到其与整体适合度间存在明显遗传协方差。取而代之的是，对性状偏差的遗传分析显示，这些性状的遗传方差相对于整体适合度存在显著的稳定选择，表明它们处于进化最优值处。在普遍存在多效性（pleiotropy）的情况下，对目标性状的稳定选择会通过选择作用于其他（通常未被测定的）性状的净效应产生，且相较于单个性状，这种选择对性状组合的作用往往更强。若性状与适合度间的环境协方差掩盖了潜在的遗传关联，则在表型分析中往往难以检测到这类选择。对性状偏差的遗传分析为检测近期元分析（metaanalyses）中所推断的缺失稳定选择提供了可行途径。