Species Richness of Eruciform Larvae Associated with Native and Alien Plants in the Southeastern United States

With continued suburban expansion in the southeastern United States, it is increasingly important to understand urbanization and its impacts on natural ecosystems.  Expansion of suburbia is often coupled with replacement of native plants by alien ornamental plants such as crepe myrtle, Bradford pear, and Japanese maple.  The purpose of this project was to conduct an analysis of existing larval Lepidoptera and Symphyta hostplant records in the southeastern United States, comparing their species richness on common native and alien woody plants.  We found that, in most cases, native plants have the capability of supporting more species of eruciform larvae compared to aliens.  Alien congener plant species (those in the same genus as native species) supported more species of larvae than alien, non-congeners.  Most of the larvae that feed on alien plants are generalist species.  However, most of the specialist species feeding on alien plants use congeners of native plants, providing evidence of a spillover, or false spillover effect.  These results are concordant with those predicted by the Enemy Release Hypothesis, which states that alien plants are more successful in non-native areas due to reduced herbivore attack.  We suggest that people associate landscape plants with both aesthetic value and ecological function.