Your enemy may be my friend: invasive legume attracts exotic herbivore in a tallgrass prairie.
Effects of invasive exotic plants on plant communities are often profound, but interactions with higher trophic levels are less evident. Postulated effects of invasive plants on arthropods include increased abundances of herbivores through refuge and improved microclimate, facilitation of other exotic species, and altered arthropod diversity. We examined the impact on the arthropod community by Lespedeza cuneata, an exotic legume with dense, chemically defended foliage, by comparing arthropod numbers in unmanipulated 1-m2 plots with L. cuneata shoots (= control) to arthropod numbers in plots from which shoots of L. cuneata were removed. Lespedeza cuneata removal produced no overall effect on arthropod abundance, but an invasive herbivore, Popillia japonica (Japanese Beetle), was twice as abundant in plots with L. cuneata. Lespedeza cuneata removal increased arthropod evenness in May then decreased it through the summer. In a second experiment we quantified chewing herbivory by placing individual potted plants from five native prairie species and L. cuneata within these same removal/no removal plots for 4 weeks. Removal of L. cuneata shoots from plots did not significantly affect herbivory of tagged leaves from the native species. However, entire L. cuneata leaves or plants disappeared more frequently regardless of plot treatment. Invasion by this exotic legume is likely due to direct effects on native plants, but indirect effects through facilitation of an exotic herbivore could contribute to its success in some areas.