Submitted to: Oecologia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/4/1999
Publication Date: N/A
Interpretive Summary: Leaf-miningfliesareseriousagriculturalpestsofawidevarietyof agricultural and ornamental crops. This research examines the evolutionary potential of the recently introduced leaf-mining fly Amauromyza flavifrons to become a pest of sugar beets. Currently, female flies lay eggs into sugar beets, but most larvae die after feeding on this plant. Experiments foundthatA.flavifronsintheUnitedStatespossessgeneticvariationin egg-laying response to sugar beets, but not in the ability of larvae to toleratesugarbeettissue.Basedontheseresults,itispredictedthat natural selection will favor flies that do not lay their eggs on sugar beets. This information is of interest to entomologists and growers concerned with sugar beets and also to evolutionary biologists interested in the dynamics of pest host range evolution.
Technical Abstract: From both theoretical and experimental work, it is well-known that genetic variation is necessary for adaptive evolution. Less understood is to what extent the lack of genetic variation may serve as an important constraint on adaptive evolution in natural populations. Among plant feeding insects exposed to a novel or non-traditional plant species, patterns of genetic variation in both acceptance and performance on the novel plant determine whether or not the plant will be incorporated into the diet. A lack of genetic variation in either acceptance or performance can constrain the insect from evolving to feed on the plant regardless of any selective advantage. This study investigated patterns of genetic variation in host-associated characters in the leaf-mining fly Amauromyza flavifrons. This insect readily oviposits on Beta vulgaris, a non-traditional plant upon which the larvae suffer high mortality. Experiments found significant tfamily-level variation in oviposition response to B. vulgaris but not in either larval survival or growth on this plant species. In regions with high densities of B. vulgaris, it is predicted that the lack of genetic variation in larval survival and growth on this plant will constrain the adoption of this plant as a "true host plant" and, instead, females will evolve to have lower acceptance of this plant for oviposition.