The Effects of Domestication ofBrassicaandPhaseoluson the Interaction between Phytophagous Insects and Parasitoids

Domesticated plants which have been the subject of artificial selection have altered allelochemistry and nutrient content. Insects that feed on these plants, as well as the parasitoids that attack these insects, have been forced to adapt to these changes. Here we present results from two studies, one involving the herbivorePieris rapae(Lep.: Pieridae) and its parasitoidCotesia glomerata(Hym.: Braconidae), and the other involving the seed eating beetleZabrotes subfasciatus(Col.: Bruchidae) which is parasitized byStenocorse bruchivora(Hym.: Braconidae). In these studies we examined the effects of plant domestication on herbivore and parasitoid performance and on the host location behavior of parasitoids. We tested the hypothesis that as a result of plant domestication, cultivars provide a higher quality resource for herbivores and their parasitoids than their wild relatives. Results from these two studies show that, overall, herbivore and parasitoid performance was higher on cultivated plant species than on wild species. Furthermore, choice experiments revealed that parasitoids were more attracted to cultivars than to related wild plants. The higher attractiveness of cultivated plants suggests that the volatile phytochemicals used by these parasitoids during the process of host location have not been lost or reduced as a result of plant domestication. We discuss how natural selection may have operated on parasitoids to locate hosts on plants on which their performance is high.