Data from: Sexual selection on song and cuticular hydrocarbons in two distinct populations of Drosophila montana

Sexual selection has the potential to contribute to population divergence and speciation. Most studies of sexual selection in Drosophila have concentrated on a single signaling modality, usually either courtship song or cuticular hydrocarbons (CHCs), which can act as contact pheromones. We have examined the relationship between both signal types and reproductive success using F1-3 offspring of wild-collected flies, raised in the lab. We used two populations of the Holarctic species Drosophila montana, that represent different phylogeographic clades which have been separate for ca. 0.5 MY, and which differ to some extent in both traits. Here we characterise the nature and identify the targets of sexual selection on song, CHCs and both traits combined within the populations. Three measures of courtship outcome were used as fitness proxies. They were the probability of mating, mating latency and the production of rejection song by females and showed patterns of association with different traits that included both linear and quadratic selection. Courtship song predicted courtship outcome better than CHCs and the signal modalities acted in an additive rather than synergistic manner. Selection was generally consistent in direction and strength between the two populations and favoured males that sang more vigorously. Sexual selection differed in the extent, strength and nature on some of the traits between populations. However, the differences in the directionality of selection detected were not a good predictor of population differences. In addition, a character previously shown to be important for species recognition, interpulse interval, was found to be under sexual selection. Our results highlight the complexity of understanding the relationship between within-population sexual selection and population differences. Sexual selection alone cannot predict differences between populations.

性选择有可能推动种群分化与物种形成。目前针对果蝇属（Drosophila）性选择的多数研究仅聚焦于单一信号模态，通常为求偶歌或可作为接触信息素的表皮碳氢化合物（cuticular hydrocarbons, CHCs）。本研究以野外采集、实验室饲养的野生果蝇F1至F3代后代为实验材料，探究了这两类信号类型与繁殖成功率之间的关联。实验所用的全北界物种山生果蝇（Drosophila montana）的两个种群分属不同的系统地理支系，二者分化时长约为50万年，且在上述两类性状上均存在一定差异。本研究在两个种群内部分别解析了针对求偶歌、表皮碳氢化合物（CHCs）以及二者组合的性选择本质，并确定了其作用靶标。研究采用三项求偶结局指标作为适合度替代指标，分别为交配成功率、交配潜伏期以及雌性拒绝鸣唱的产生情况，这些指标与不同性状的关联模式涵盖了线性选择与二次选择。结果显示，求偶歌对求偶结局的预测能力优于表皮碳氢化合物（CHCs），且两类信号的作用方式为加性效应而非协同效应。两个种群的性选择在方向与强度上总体保持一致，均青睐鸣唱更旺盛的雄性；但不同种群间在部分性状上的性选择范围、强度及本质存在差异。然而，本研究观测到的选择方向差异，并不能有效预测种群间的分化差异。此外，此前被证实与物种识别相关的性状——脉冲间期（interpulse interval）——被发现处于性选择的作用之下。本研究结果凸显了解析种群内性选择与种群分化之间关联的复杂性，仅依靠性选择无法准确预测种群间的分化差异。