Department of Neurobiology and Behavior, Cornell University, Ithaca, New York, USA.
J Evol Biol. 2022 Jan;35(1):109-123. doi: 10.1111/jeb.13951. Epub 2021 Oct 28.
Sexual signalling traits are often observed to diverge rapidly among populations, thereby playing a potentially key early role in the evolution of reproductive isolation. While often assumed to reflect divergent sexual selection among populations, patterns of sexual trait diversification might sometimes be biased along axes of standing additive genetic variation and covariation among trait components. Additionally, theory predicts that environmentally induced phenotypic variation might facilitate rapid trait evolution, suggesting that patterns of divergence between populations should mirror phenotypic plasticity within populations. Here, we evaluate the concordance between observed axes of multivariate sexual trait divergence and predicted divergence based on (1) interpopulation variation in sexual selection, (2) additive genetic variances and (3) temperature-related phenotypic plasticity in male courtship song among geographically isolated populations of the Hawaiian swordtail cricket, Laupala cerasina, which exhibit sexual isolation due acoustic signalling traits. The major axis of multivariate divergence, d , accounted for 76% of variation among population male song trait means and was moderately correlated with interpopulation differences in directional sexual selection based on female preferences. However, the majority of additive genetic variance was largely oriented away from the direction of divergence, suggesting that standing genetic variation may not play a dominant role in the patterning of signal divergence. In contrast, the axis of phenotypic plasticity strongly mirrored patterns of interpopulation phenotypic divergence, which is consistent with a role for temperature-related plasticity in facilitating instead of inhibiting male song evolution and sexual isolation in these incipient species. We propose potential mechanisms by which sexual selection might interact with phenotypic plasticity to facilitate the rapid acoustic diversification observed in this species and clade.
性信号特征通常在种群之间迅速分化，因此在生殖隔离的进化中发挥了潜在的关键早期作用。虽然通常假定反映了种群之间不同的性选择，但性特征多样化的模式有时可能会沿着种群的附加遗传变异和特征成分之间的协变的轴发生偏差。此外，理论预测环境诱导的表型变异可能促进快速的特征进化，这表明种群之间的分歧模式应该反映种群内部的表型可塑性。在这里，我们评估了观察到的多元性特征分歧的轴与基于（1）性选择中的种群间变异，（2）加性遗传方差和（3）温度相关的表型可塑性在地理隔离的夏威夷剑尾蟋蟀，Laupala cerasina 种群之间的分歧的预测分歧之间的一致性，这些种群由于声学信号特征而表现出性隔离。多元分歧的主轴，d，占种群雄性歌曲特征平均值差异的 76%，并且与基于雌性偏好的种群间定向性选择的差异中度相关。然而，大部分加性遗传方差主要偏离分歧的方向，这表明现有遗传变异可能在信号分歧的模式中没有起主导作用。相比之下，表型可塑性的轴强烈反映了种群间表型分歧的模式，这与温度相关的可塑性在促进而不是抑制雄性歌曲进化和这些初生物种的性隔离中的作用一致。我们提出了性选择可能与表型可塑性相互作用的潜在机制，以促进该物种和类群中观察到的快速声学多样化。
