The genetics and mechanisms of parasitoid host specificity

Introduced parasitoids reduce the impact of invasive pests. Critics argue that introduced parasitoids may evolve to attack native species and native parasitoids may switch to control invasive pests, eliminating the need for introductions. We review evidence about responses to selection on host specificity and the genetics of host specificity. Parasitoids do respond to selection for parasitizing novel hosts, but responses are limited. Populations vary in host specificity, indicating local adaptation, but variation is small. Several factors impede research on this topic. The meanings of terms differ among studies. Furthermore, few researchers work on the subject. Systems need multiple attributes: medium-sized genomes, short generation times, laboratory behavior resembling the field, easy rearing, and multiple recently diverged populations varying in host specificity. We suggest uniform definitions, systems suitable for laboratory study, and studies of selection in naturally occurring populations. The evidence suggests that the evolution of host specificity among introduced parasitoids is limited.