Sexual selection and population divergence II. divergence in different sexual traits and signal modalities in field crickets (Teleogryllus oceanicus)

Sexual selection can target many different types of traits. However, the relative influence of different sexually-selected traits during evolutionary divergence is poorly understood. We used the field cricket Teleogryllus oceanicus to quantify and compare how five traits from each of three sexual signal modalities and components diverge among allopatric populations: male advertisement song, cuticular hydrocarbon (CHC) profiles and forewing morphology. Population divergence was unexpectedly consistent: we estimated the among-population (genetic) variance-covariance matrix, D, for all 15 traits, and Dmax explained nearly two-thirds of its variation. CHC and wing traits were most tightly integrated, whereas song varied more independently. We modelled the dependence of among-population trait divergence on genetic distance estimated from neutral markers to test for signatures of selection vs. neutral divergence. For all three sexual trait types, phenotypic variation among populations was largely explained by a neutral model of divergence. Our findings illustrate how phenotypic integration across different types of sexual traits might impose constraints on the evolution of mating isolation and divergence via sexual selection.

性选择可作用于多种不同的性状类型。然而，在进化分化过程中，不同经性选择塑造的性状的相对影响仍不甚明晰。本研究以田野蟋蟀（Teleogllus oceanicus）为研究对象，定量比较了三类性信号模态及其组分中各5个性状在异域种群间的分化模式：雄性广告鸣曲、表皮碳氢化合物（CHC）谱以及前翅形态。种群分化模式出乎意料地一致：我们为全部15个性状估算了种群间（遗传）方差-协方差矩阵D，其中Dmax可解释该矩阵近三分之二的变异。表皮碳氢化合物与翅部性状的整合程度最高，而鸣曲性状的变异则相对更为独立。我们构建了种群间性状分化对基于中性遗传标记估算的遗传距离的依赖模型，以检验分化是受选择作用还是中性分化的信号。针对三类性性状类型，种群间的表型变异在很大程度上可通过中性分化模型得到解释。本研究结果阐明了不同类型性性状间的表型整合可能如何对交配隔离的进化以及性选择驱动的分化施加约束。