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 equiva...