Lack of evidence for local adaptation to individual plant clones or site by a mobile specialist herbivore.

Abstract

Several studies have documented local adaptation by sedentary insects to individual phenotypes of their host plants. Here, I examined whether a similar phenomenon could be found in a mobile, specialized insect, the sumac flea beetle. Previous work has shown that sumac individuals differ in their suitability as hosts for these beetles and that differences have both an environmental and a genetic basis. Using beetle populations collected as eggs from eight different sumac clones along an east-west transect, a reciprocal transfer experiment was conducted to determine whether there was any evidence for local adaptation by beetles to individual plant clones or to site. Variables examined were larval survivorship past first instar, development time, weight at pupation and patterns of predation by enemies. While no evidence for local adaptation was found, there were significant effects of plant clone on which larvae developed, origin of the larval population and the interaction of these effects on larval performance. For larval weight at pupation, there was also some indication that trade-offs may exist in ability of larvae to use different host plant clones. In addition, there were significant environmental effects on several measures of larval performance. Predation rates differed by plant clone, but not by site or with respect to origin of larvae. While no evidence for local adaptation was found in this study, prerequisites for finding such patterns may exist in this system.