Species richness of eruciform larvae associated with native and alien plants in the southeastern United States

Abstract

With continued suburban expansion in the southeastern United States, it is increasingly important to understand urbanization and its impacts on sustainability and natural ecosystems. Expansion of suburbia is often coupled with replacement of native plants with 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. Of the larvae that feed on alien plants, most of them 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. The results of this study are concordant with that which is predicted by the enemy release hypothesis, stating that alien plants are more successful in their non-native ranges due to reduced herbivore attack. With a reduction in primary consumer diversity, secondary consumers such as migratory birds and parasitoid wasps may also be impacted. These results highlight the need for further research in this area.