Crop domestication in the solanaceae: Consequences for indirect plant defense

It is a widely held opinion that plant domestication of agricultural crops has led them to be more susceptible to insect herbivores. Selection for beneficial traits such as improved flavor and increased fruit yield may have led to a loss of plant resistant traits to herbivores via two ways. One: cultivated plants may be more susceptible to insect pests because they have compromised direct defenses, such as less foliar toxins, and/or two: loss of indirect plant defenses, such as changes in volatiles, may impair the plant's ability to attract natural enemies. However, both of these hypotheses are unfounded and poorly documented in the literature. Here, we present evidence that domestication across the Solanaceae has resulted in a loss of direct defense but improved indirect resistance to the specialist insect herbivore, Manduca sexta. Using the agricultural crops in the family Solanaceae and comparing them to their wild progenitors, we found that caterpillars performed better on domesticated than wild relatives in a crop dependent manner. Further, in behavioral choice assays with the specialist sphingid parasitoid wasp, Cotesia congregata, parasitoids preferentially chose herbivore damaged plants with an interaction between domestication and crop on wasp choice. These results taken together imply a loss of direct defense due to domestication but improved volatile signaling of natural enemies in specific agricultural solanaceous crops.