Hairpencil volatiles influence interspecific courtship and mating between two related moth species

Reproductive isolation between sympatric, closely related species can be accomplished through a variety of pre-zygotic isolating mechanisms, including courtship-signaling behavior that involves pheromones. In the moths Heliothis virescens and H. subflexa, males display abdominal hairpencils (HP), which release volatile chemicals during courtship. In this study, we demonstrated that HP volatiles released by male H. subflexa function to improve mating success with conspecific females. Interspecific mating experiments were conducted to determine any influence of HP volatiles on species isolation. Female H. virescens and H. subflexa were observed during courtship with males of the other species, following either sham-operation or ablation of HPs, both with and without concurrent presentation of HP volatiles. Mating success was improved by co-presentation of HP extract from males of the same species during courtship. Ablation of HPs improved mating between H. subflexa females and H. virescens males. During interspecific matings, male H. virescens attempted copulation less frequently in the presence of H. virescens HP extract, though H. subflexa males were not affected by the presence of H. subflexa HP extract. This suggests that HP volatiles produced by males of each species may inhibit mating between species through effects on males (H. virescens) and females (H. subflexa).