Data from: Rapid divergence of wing volatile profiles between subspecies of the butterfly Pieris rapae (Lepidoptera: Pieridae)

Complex signaling traits such as pheromone profiles can play an important role in the early stages of reproductive isolation between populations. These signals can diverge along multiple trait axes, and signal receivers are often sensitive to subtle differences in signal properties. In the Lepidoptera, prior research has highlighted that natural selection can drive rapid chemical signal divergence, for instance via mate recognition to maintain species boundaries. Much less is known about the occurrence of such changes for predominantly sexually-selected chemical signals, such as those released by many male lepidopterans. We evaluated the divergence in male and female wing volatile profiles between two recently-isolated subspecies of the pierid butterfly Pieris rapae: Pieris rapae rapae and Pieris rapae crucivora. In laboratory settings, these subspecies exhibit strong pre-mating isolation, with females rejecting males of the opposite subspecies despite the fact that males direct equivalent courtship effort toward females of either subspecies. Using gas chromatography-mass spectrometry, we analyzed the volatile chemical profiles of individual males and females of each subspecies. We find that males of each subspecies differ in their wing volatile profiles, including quantitative differences in a male sex pheromone, ferrulactone. In contrast, female wing volatiles profiles have diverged significantly less. These sex-specific patterns suggest that male chemical profiles may play a role in the observed pre-mating isolation between these two subspecies, providing support for future investigations of sexually-selected chemical traits in population divergence.

诸如信息素谱（pheromone profiles）这类复杂的信号性状，在种群间生殖隔离的早期阶段可发挥关键作用。这类信号可沿多个性状维度发生分化，而信号接收者往往对信号属性的细微差异极为敏感。在鳞翅目（Lepidoptera）昆虫中，既往研究已证实自然选择可推动化学信号快速分化——例如通过配偶识别机制维系物种边界。然而，针对多数由性选择主导的化学信号（如多数雄鳞翅目昆虫释放的信号）而言，这类分化的发生情况仍鲜有研究。本研究针对粉蝶科（Pieridae）菜粉蝶（Pieris rapae）的两个新近分化亚种：菜粉蝶指名亚种（Pieris rapae rapae）与菜粉蝶十字纹亚种（Pieris rapae crucivora），分析了雌雄个体翅部挥发性谱的分化情况。实验室条件下，这两个亚种表现出强烈的交配前生殖隔离：尽管雄蝶对两个亚种的雌蝶均投入同等的求偶行为，但雌蝶会拒绝异亚种的雄蝶。本研究采用气相色谱-质谱联用法（gas chromatography-mass spectrometry），对两个亚种雌雄个体的翅部挥发性化学谱进行了分析。结果显示，各亚种雄蝶的翅部挥发性谱存在显著差异，其中包括雄虫性信息素阿魏酸内酯（ferrulactone）的含量差异。相较而言，雌蝶的翅部挥发性谱分化程度则显著更低。这种性特异性分化模式表明，雄蝶的化学信号谱可能在上述两个亚种间的交配前生殖隔离中发挥作用，为后续探索性选择化学性状在种群分化中的作用提供了研究支撑。