GENETIC COVARIANCE BETWEEN OVIPOSITION PREFERENCE AND LARVAL PERFORMANCE IN AN INSECT HERBIVORE.

An experimental study determined that females of the herbivorous fly species Liriomyza sativae (Diptera: Agromyzidae) preferentially oviposit on the plant species on which their female progeny attain the greatest pupal weight. A modified parent/offspring regression was used to quantify this relationship as an additive genetic covariance between host-plant preference and relative performance of female larvae on different plant species. The implications of a genetic covariance between preference and performance on the course of evolution in herbivores are discussed. Several females from one population refused to oviposit on one of the plant species; this population also suffered the only significant larval mortality on this plant. These results corroborate the avoidance of unsuitable host plants seen in the genetic analyses of individuals, but relative to the genetic data, such population-level data are of limited usefulness in the study of evolutionary mechanisms by which insect populations become adapted to their host plants.