Domesticated non-native species may have high invasion risk because they have been intentionally introduced to new ranges and selected for specific traits. However, little is known about whether traits selected for during domestication confer competitive advantages or enhance plant resistance or tolerance to herbivory. We experimentally evaluated invasion risk of different cultivars of Lespedeza cuneata (Chinese bushclover), a perennial legume domesticated for forage and erosion control, compared to wild type populations of the species that have escaped and spread throughout much of the midwestern and eastern United States. Domesticated L. cuneata cultivars have varying levels of tannins and productivity resulting from selection for improved palatability and health benefits for livestock, which may influence invasion risk. To test the performance and fitness of L. cuneata cultivars compared to wild type populations, we conducted a factorial greenhouse experiment with treatments of competition with native plant species and herbivory by a generalist herbivore (Spodoptera frugiperda). A no-choice feeding bioassay that included the generalist herbivore and a wide range of L. cuneata wild type populations and cultivars also was conducted to determine how potential differences in foliar defensive chemistry among L. cuneata cultivars and populations might influence generalist herbivore pressure.
Results/Conclusions
NMDS ordination analyses revealed that domesticated and wild type Lespedeza cuneata responded differently under competition and herbivory treatments. Wild type L. cuneata was consistently larger than any of the cultivars under one or in the absence of competition and herbivory. However, the wild type plants were of similar size to those of the cultivars under the combined stress of competition and herbivory. The three L. cuneata cultivars all responded similarly to the treatments. Results of the feeding bioassay revealed that S. frugiperda feeding on the two cultivars with reduced tannins and the wild type L. cuneata from the invaded range weighed more than those feeding on the highest tannin cultivar, native range wild type populations, or native congener. Survivorship of the S. frugiperda was higher for those fed the lower tannin cultivars, and the most deaths occurred for those feeding on the highest tannin cultivar and the native congener. Furthermore, cultivars with more chemical defenses were consumed less often than certain wild type populations.