Selection responses and quantitative‐genetic analysis of preadult performance on two host plants in the bean weevil, Acanthoscelides obtectus

Abstract

AbstractThe most popular hypothesis that explains host specialization in herbivorous insects assumes the presence of a genetic trade‐off in larval performance across host plant species. We examined whether there is a genetic trade‐off in preadult performance traits on two hosts in the bean weevil, Acanthoscelides obtectus Say (Coleoptera: Bruchidae). Well‐established laboratory populations of A. obtectus were maintained on two plant species, one being the native host (bean) and the other a novel, unsuitable host (chickpea). After 50 generations of laboratory rearing, preadult survival and development time on each host plant were compared between the two populations. A split‐brood design was used to estimate cross‐host genetic correlations in the two traits and to compare the populations in their patterns of genetic variation over the two plants. We detected a survival cost paid by A. obtectus on its native host for the increasing adaptation to the novel one, and a significant population × host interaction for survival. The host effect on survival was significant in the bean‐adapted population. The additive genetic variances for survival and female development time were only expressed on the novel host, and the half‐sib family mean correlations across hosts were zero for both traits in both populations. However, the sire × host interaction for survival was not recorded in either population, whereas the sire × host interaction and non‐additive genetic variance for development time evolved during the selection on the novel host.