Complex Chemical Information Networks in Tritrophic Communities

Abstract

In response of damage by herbivores, plants are known to emit volatiles that enhance the effectiveness of carnivorous natural enemies of herbivores. Studies on plant-carnivore interactions mediated by such infochemicals have focused on tritrophic systems in which plants are infested by a single herbivore species. In natural ecosystems, however, plants are often simultaneously infested by several herbivorous species. Here, we focus on two herbivore species that simultaneously attack crucifer plants, and their respective specialist parasitic wasps. We first show the specific responses of the two specialist parasitic wasps to infochemicals originated from cabbage plants infested by each of their respective host larvae. We then coupled the two tritrophic systems on the same plants. These experiments demonstrated the presence of indirect interactions between the two herbivore species. Overall, the results indicate the presence of infochemical-mediated indirect interaction networks on a single plant, and a filed community of herbivores can be better understood from the perspective of such interaction networks.