Data from: Sexual selection and assortative mating: an experimental test

Mate choice and mate competition can both influence the evolution of sexual isolation between populations. Assortative mating may arise if traits and preferences diverge in step, and, alternatively, mate competition may counteract mating preferences and decrease assortative mating. Here, we examine potential assortative mating between populations of Drosophila pseudoobscura that have experimentally evolved under either increased (‘polyandry’) or decreased (‘monogamy’) sexual selection intensity for 100 generations. These populations have evolved differences in numerous traits, including a male signal and female preference traits. We use a two males: one female design, allowing both mate choice and competition to influence mating outcomes, to test for assortative mating between our populations. Mating latency shows subtle effects of male and female interactions, with females from the monogamous populations appearing reluctant to mate with males from the polyandrous populations. However, males from the polyandrous populations have a significantly higher probability of mating regardless of the female's population. Our results suggest that if populations differ in the intensity of sexual selection, effects on mate competition may overcome mate choice.

配偶选择与配偶竞争均可影响种群间性隔离的演化进程。若性状与配偶偏好同步分化，则可能出现选型交配（assortative mating）；反之，配偶竞争或可抵消配偶偏好，削弱选型交配的发生。本研究以经历100代实验演化的伪暗果蝇（Drosophila pseudoobscura）种群为研究对象，这些种群分别在增强性选择强度（多配制polyandry）或减弱性选择强度（单配制monogamy）的条件下完成演化。目前，这些种群已在诸多性状上产生演化差异，涵盖雄性信号与雌性偏好性状。我们采用两雄一雌实验设计，使配偶选择与配偶竞争均可对交配结果产生影响，以此检验各试验种群间是否存在选型交配。交配潜伏期体现了雌雄个体间交互作用的细微效应，单配制种群的雌性表现出不愿与多配制种群雄性交配的倾向。但无论雌性的种群来源如何，多配制种群的雄性均具有显著更高的交配成功率。本研究结果表明，若不同种群的性选择强度存在差异，配偶竞争所带来的效应或可凌驾于配偶选择之上。