Crop domestication is the process of artificially selecting plants to increase their suitability to human requirements: taste, yield, storage, and cultivation practices. There is increasing evidence that crop domestication can profoundly alter interactions among plants, herbivores, and their natural enemies. Overall, little is known about how these interactions are affected by domestication in the geographical ranges where these crops originate, where they are sympatric with the ancestral plant and share the associated arthropod community. In general, domestication consistently has reduced chemical resistance against herbivorous insects, improving herbivore and natural enemy performance on crop plants. More studies are needed to understand how changes in morphology and resistance-related traits arising from domestication may interact with environmental variation to affect species interactions across multiple scales in agroecosystems and natural ecosystems.

Parasitoids are insects that spend their immature stages feeding from the tissues of other arthropods, eventually killing them. Many insects that serve as hosts for parasitoids are herbivorous, and metabolites from plants on which they feed can influence both the location of hosts by adult parasitoids and the development of the immature stages. For example, adult female parasitoids, which have the formidable task of locating often scarce and well-hidden hosts, may make effective use of chemical signals that plants emit in response to herbivory. The signals are used to guide them to herbivores that are damaging the plants. Also, plant-produced toxins along with digestibility reducers may slow down herbivore development, prolonging the time that they are vulnerable to parasitoids. The influence of plant chemicals continues after a parasitoid egg has been deposited in or on a host. An immature parasitoid uses the host as its sole source of nutrients. As the diet of hosts, plants can affect their development and physiological condition and thus, the overall suitability and quality of hosts as resources for parasitoid larvae. Here we give an overview of what is known about these interactions between plants and parasitoids and speculate on the possibility that parasitoids and other natural enemies of herbivorous arthropods may have, to some extent, contributed to the evolutionary pressures from which plant chemical traits have evolved.