Chemical mediation of coevolution: Phylogenetic evidence for Apiaceae and associates

The chemical diversity of the Apiaceae has made the family of particular significance in discussions of plant/insect interactions for close to a century. As forbs with distinctive chemistry and a specialized insect fauna, species in the Apiaceae and their associated herbivores represent an ideal system for examining competing hypotheses accounting for hostplant acquisition patterns. Comparisons of the phylogenetic history of colonization of Apiaceae across a number of taxa reveal that host shifts to the family originate in only a narrow range of taxa; chemical similarities among those taxa, rather than geographic proximity or phylogenetic relationships, are the most plausible basis for the observed host shifts. Similar ecologies among species in this narrow range of taxa, including similar herbivore faunas, may well account for similarities in overall chemical profiles. The patterns documented here are consistent with reciprocal coevolutionary interactions between herbivorous insects and their hostplants.