Evolution of divergent female mating preference in response to experimental sexual selection

Sexual selection is predicted to drive the coevolution of mating signals and preferences (mating traits) within populations, and could play a role in speciation if sexual isolation arises due to mating trait divergence between populations. However, few studies have demonstrated that differences in mating traits between populations result from sexual selection alone. Experimental evolution is a promising approach to directly examine the action of sexual selection on mating trait divergence among populations. We manipulated the opportunity for sexual selection (low versus high) in populations of Drosophila pseudoobscura. Previous studies on these experimental populations have shown that sexual selection manipulation resulted in the divergence between sexual selection treatments of several courtship song parameters, including IPI (inter-pulse interval) which markedly influences male mating success. Here, we measure female preference for IPI using a playback design to test for preference divergence between the sexual selection treatments after 130 generations of experimental sexual selection. The results suggest that female preference has coevolved with male signal, in opposite directions between the sexual selection treatments, providing direct evidence of the ability of sexual selection to drive the divergent coevolution of mating traits between populations. We discuss the implications in the context sexual selection and speciation.

性选择被认为会推动种群内交配信号与交配偏好（统称交配性状）的协同演化；若种群间因交配性状分化产生性隔离，则性选择可能在物种形成过程中发挥作用。然而，鲜有研究证实种群间的交配性状差异仅由性选择所致。实验演化是直接探究性选择对种群间交配性状分化作用的极具前景的研究手段。我们在伪暗果蝇（Drosophila pseudoobscura）种群中操控了性选择的作用强度（分为低、高两组）。过往针对这些实验种群的研究表明，对性选择的操控已导致两组性选择处理下的多项求偶鸣声参数出现分化，其中包括显著影响雄性交配成功率的IPI（脉冲间间隔，inter-pulse interval）。本研究通过回放实验设计，量化雌性对IPI的偏好，以检验经过130代实验性选择后，两组性选择处理下的雌性偏好是否出现分化。结果显示，雌性偏好与雄性信号发生了协同演化，且两组性选择处理下的演化方向相反，这为性选择能够推动种群间交配性状的分化性协同演化提供了直接证据。我们将在性选择与物种形成的研究框架下，探讨本研究的理论启示。