Data from: Insect mating signal and mate preference phenotypes covary among host plant genotypes

Sexual selection acting on small initial differences in mating signals and mate preferences can enhance signal-preference co-divergence and reproductive isolation during speciation. However, the origin of initial differences in sexual traits remains unclear. We asked whether biotic environments, a source of variation in sexual traits, may provide a general solution to this problem. Specifically, we asked whether genetic variation in biotic environments provided by host plants can result in signal-preference phenotypic covariance in a host-specific, plant-feeding insect. We used a member of the Enchenopa binotata species complex of treehoppers (Hemiptera: Membracidae) to assess patterns of variation in male mating signals and female mate preferences induced by genetic variation in host plants. We employed a novel implementation of a quantitative genetics method, rearing field-collected treehoppers on a sample of naturally-occurring replicated host plant clone lines. We found remarkably high signal-preference covariance among host plant genotypes. Thus, genetic variation in biotic environments influences the sexual phenotypes of organisms living on those environment in a way that promotes assortative mating among environments. This consequence arises from conditions likely to be common in nature (phenotypic plasticity and variation in biotic environments). It therefore offers a general answer to how divergent sexual selection may begin.

性选择（Sexual selection）作用于交配信号与配偶偏好的初始微小差异时，可在物种形成过程中推动信号-偏好协同分化与生殖隔离的强化。然而，性征初始差异的起源至今仍未阐明。我们针对“作为性征变异来源的生物环境（biotic environments）能否为该问题提供普适性解答”这一问题展开探究。具体而言，我们旨在明确：寄主植物所赋予的生物环境的遗传变异，是否能在一种寄主专一性植食性昆虫中引发信号-偏好表型协方差（signal-preference phenotypic covariance）。我们选取半翅目（Hemiptera）角蝉科（Membracidae）二点埃蝉（Enchenopa binotata）物种复合体中的一个类群，用以评估寄主植物遗传变异所诱导的雄性交配信号与雌性交配偏好的变异模式。我们采用了一种创新性的数量遗传学（quantitative genetics）方法应用路径：将野外采集的角蝉饲养于一组自然存在的重复寄主植物无性系株系中。实验结果显示，不同寄主植物基因型间的信号-偏好协方差极高。由此可见，生物环境的遗传变异会对栖息于此类环境中的生物的性表型产生影响，其作用机制可促进不同环境间的选型交配（assortative mating）。这一结论源于自然界中普遍存在的两类条件——表型可塑性（phenotypic plasticity）与生物环境变异，因此为歧化性选择（divergent sexual selection）的起始机制提供了普适性解答。