Potential Evolution of Host Range in Herbivorous Insects

Abstract

Many clades of herbivorous insects are remarkably conservative in the plants that they attack, and in many groups, related insects tend to feed on related plants. However, rapid evolution of host range has been documented in several species. Managers who contemplate introducing a host-specific insect for biological control of a weed would like to predict whether or not the species to be introduced poses an appreciable risk that it might evolve rapidly in host range and adapt to non-target plants. Guidelines as to which plants might most readily be incorporated into the insect’s diet may be provided, in some cases, by their phylogenetic relationship to the insect’s normal host and by the diet of insects closely related to the proposed control agent. The likelihood of rapid evolution of a shift to a non-target plant may be judged to some extent by screening populations of the insect for genetic variation in behavioral responses to and performance on the plant, since genetic variation is the prerequisite for evolutionary change.