Genetic constraints and the phylogeny of insect-plant associations: responses of Ophraella communa (Coleoptera: Chrysomelidae) to host plants of its congeners

Abstract

Ophraella communa feeds chiefly, and in E North America exclusively, on Ambrosia (Asteraceae). The authors screened for genetic variation in feeding responses to and larval survival on its own host and on seven other plants that are hosts (or, in one case, closely related to the host) of other species of Ophraella. There was evidence for genetic variation in feeding responses to five of the seven test plants, other than the natural host, but no evidence of genetic variation in feeding responses to two plant species, nor in capacity for larval survival on six. Results are interpreted in the context of a provisional phylogeny of, and a history of host shifts within, the genus. By far the greatest potentiality for adaptation to a congener's host was evinced in responses to Iva frutescens, which not only is related and chemically similar to Ambrosia, but also is the host of a closely related species of Ophraella that may have been derived from an Ambrosia-associated ancestor. Results offer support for the hypothesis that the evolution of host shifts has been guided in part by constrained genetic variation. -from Authors