Inbreeding in horsenettle (Solanum carolinense) alters nocturnal plant volatile emissions that guide oviposition by specialist herbivores

Plants release volatile organic compounds in the course their normal physiological activities, and these constitutive emissions can serve as foraging and oviposition cues for insect herbivores. It is, however, not known whether within species genetic variation for volatile emission affects the foraging or oviposition behavior of herbivores. Here, we examined the nocturnal volatile compounds emitted by inbred and outbred plants from three families of horsenettle plants, Solanum carolinense. We found that the outbred plants produced more total volatiles and a greater number of volatile compounds than the inbred plants, including some that are known moth repellants and some that attract predaceous insects. We next examined the oviposition preferences of Manduca sexta moths, whose larvae are specialists on the Solanaceae. We found that the moths overwhelmingly chose to oviposit on the inbred plants and spent significantly more time on inbred plants. In the second oviposition preference test, the plants were enclosed in several layers of green bridal veil that permit volatiles to escape but prevent tactile or taste perception by the moths. We found that the moths overwhelmingly chose to oviposit on the bridal veil enclosing inbred plants, suggesting that the moths were responding to the volatiles emitted from inbred and outbred plants. These findings, when combined with our previous studies showing that inbreeding reduces herbivore resistance under field conditions and that larvae feeding on inbred plants grow faster than larvae on outbred plants, suggest that volatiles contain information on the suitability of the plants as food sources for offspring.