Invasive Plants Have Higher Resistance to Native Generalist Herbivores Than Exotic Noninvasive Congeners

Research on the invasive plant Phytolacca americana (L.) mostly focuses on its medicinal value and enrichment of heavy metals. However, little is known regarding its impact on native herbivorous insects. In this study, we explored the effects of P. americana and the exotic noninvasive Phytolacca icosandra (L.) on the Spodoptera litura (Fabricius) (native tobacco cutworm) via bioassay, oviposition preference, detoxifying enzyme activity analysis, and phytochemical determination. We found that the oviposition preference index (OPI) of S. litura feeding on P. icosandra was higher than that of P. americana. The developmental duration of S. litura feeding on P. icosandra was shorter than that of P. americana. Additionally, the Acetylcholinesterase (AchE) and Glutathione-S-transferase (GST) activities of S. litura feeding on P. americana were higher than that of S. litura feeding on artificial diets or P. icosandra. The content of lignin and flavonoids in P. americana was relatively high, whereas starch content was relatively low. These findings suggest invasive plants have higher resistance to herbivores, thereby suffering less damage than exotic noninvasive plants.