Herbivorous insects: model systems for the comparative study of speciation ecology.

Does ecological divergence drive species-level evolutionary diversification? How so and to what degree? These questions were central to the thinking of the evolutionary synthesis. Only recently, however, has the ecology of speciation become an important focus of empirical study. Here, we argue that ecologically specialized, phylogenetically diverse, and experimentally tractable herbivorous insect taxa offer great opportunities to study the myriad mechanisms by which ecology may cause reproductive isolation and promote speciation. We call for the development and integrated experimental study of a taxonomic diversity of herbivore model systems and discuss the availability and recent evaluation of suitable taxa. Most importantly, we describe a general comparative framework that can be used to rigorously test a variety of hypotheses about the relative contributions and the macroevolutionary generality of particular mechanisms. Finally, we illustrate important issues for the experimental analysis of speciation ecology by demonstrating the consequences of specialized host associations for ecological divergence and premating isolation in Neochlamisus bebbianae leaf beetles.