Multi-trophic interactions involving plant defenses against herbivores (mostly chemical, but other traits as well) and their interactions with parasitoids. I am very interested in how the functions of these trophic relationships compare in native and introduced habitats (e.g. Copidosoma sosares, parsnip webworms, and wild parsnip in western Europe and western US) as well as between natural and agricultural settings (e.g. comparing tri-trophic interactions among native, introduced and cultivated populations of crucifers, their herbivores, and their natural enemies; comparing tri-trophic interactions involving wild and cultivated populations of sunflower).