Abstract
Ecological communities are profoundly structured by indirect interactions among species. Understanding how these interactions work, provides important insights into community organisation and how we could interfere with community function to achieve sustainable pest management in agro-ecosystems. In plant-insect associations, indirect interactions are frequently mediated by the plant. For example, plants respond to herbivory by producing herbivore-induced plant volatiles (HIPVs) that may attract enemies of the herbivore such as parasitic wasps (parasitoids) widely used in biological control. However, also hyperparasitoids that lay eggs in the larvae of parasitoids may rely on HIPVs in host location. Caterpillars in which parasitoid larvae develop induce different HIPVs than healthy caterpillars and the interaction network of parasitoid-herbivore-plant thereby allows hyperparasitoids to locate their host. The mechanisms that underlie the interaction network are largely unknown. Our exciting unpublished data hint that parasitic wasps affect elicitors in caterpillar saliva that affect HIPV emission. Also aphids, which induce widely different responses in plants compared to caterpillars, host communities of hyperparasitoids. Our pilot studies suggest that similar interaction networks may shape plant-aphid-parasitoid-hyperparasitoid trophic chains. By using a multidisciplinary approach that integrates molecular, chemical, behavioural and field ecology, this proposed project aims to mechanistically understand interaction networks involved in hyperparasitoid host location. It will unravel how parasitoids of caterpillars and aphids initiate interaction networks across four trophic levels. The project thereby provides novel mechanistic fundamental insights into the role of indirect interaction networks in community organisation and these insights will aid in tackling the negative impact of hyperparasitoids on biological control.
Netherlands