Phylogenetic studies of insect-plant interactions: Insights into the genesis of diversity.

Phylogenetic analyses (and related historical evidence) can be used to test hypotheses about the oppurtinity for coevolution among plants and insect herbivores, the role of plant chemistry in mediating host shifts, the reality of coevolutionary 'arms races', and the role of novel defensive or counterdefensive characteristics in enhancing rates of diversification. Recent analyses provide evidence on each of these hypotheses. The strong phylogenetic component in many insect-plant associations suggests that host shifts by insects are often strongly constrained, that insect diets may not be 'optimal', and that the trophic structure and species diversity of local communities strongly reflect evolutionary history.