Data from: Reduced genetic variance among high fitness individuals: inferring stabilizing selection on male sexual displays in D. serrata

Directional selection is prevalent in nature yet phenotypes tend to remain relatively constant, suggesting a limit to trait evolution. However, the genetic basis of this limit is unresolved. Given widespread pleiotropy, opposing selection on a trait may arise from the effects of the underlying alleles on other traits under selection, generating net stabilizing selection on trait genetic variance. These pleiotropic costs of trait exaggeration may arise through any number of other traits, making them hard to detect in phenotypic analyses. Stabilizing selection can be inferred, however, if genetic variance is greater among low compared to high fitness individuals. We extend a recently suggested approach to provide a direct test of a difference in genetic variance for a suite of cuticular hydrocarbons (CHCs) in Drosophila serrata. Despite strong directional sexual selection on these traits, genetic variance differed between high and low fitness individuals and was greater among the low fitness males for seven of eight CHCs, significantly more than expected by chance. Univariate tests of a difference in genetic variance were non-significant but likely have low power. Our results suggest that further CHC exaggeration in D. serrata in response to sexual selection is limited by pleiotropic costs mediated through other traits.

定向选择（Directional selection）在自然界中普遍存在，但生物表型往往维持相对稳定，这暗示性状进化存在上限。然而，这一上限的遗传基础尚未阐明。鉴于多效性（pleiotropy）广泛存在，某一性状所受的对立选择，可能源于控制该性状的等位基因（alleles）对其他受选择性状的作用，最终对该性状的遗传方差（genetic variance）产生净稳定选择（stabilizing selection）效应。这类性状强化过程中的多效性代价可通过任意数量的其他性状产生，因此在表型分析中难以被检测。不过，若低适合度（fitness）个体的遗传方差高于高适合度个体，则可推断存在稳定选择。我们拓展了近期提出的研究方法，对果蝇Drosophila serrata的一组表皮碳氢化合物（cuticular hydrocarbons, CHCs）的遗传方差差异开展直接检验。尽管这些性状受到强烈的定向性选择，但高、低适合度个体的遗传方差仍存在显著差异：低适合度雄性的8种表皮碳氢化合物中有7种的遗传方差更高，这一结果显著高于随机预期水平。单变量（univariate）遗传方差差异检验未达到统计学显著性，但该检验的效力大概率较低。本研究结果表明，在性选择（sexual selection）驱动下，果蝇Drosophila serrata表皮碳氢化合物的进一步强化受到了通过其他性状介导的多效性代价的限制。