Antagonistic Interaction Between Microplastics and Herbivory on the Growth of Native and Invasive Plants

Microplastic pollution and herbivory are increasingly recognized as significant stressors in terrestrial ecosystems, yet their interactive effects on native and invasive plants remain poorly understood. In this study, we investigated the individual and combined effects of polyethylene microplastics (PE-MPs) and herbivory by <i>Helicoverpa armigera</i> on the growth and functional traits of twelve plant species (six invasive and six native). Exposure to PE-MPs significantly reduced biomass accumulation, with larger reductions in shoot, root, and total biomass for native plants than for invasive ones. Herbivory also significantly reduced biomass accumulation. When combined, PE-MPs and herbivory produced antagonistic effects on shoot, root, and total biomass. No significant three-way interaction was found among PE-MPs, herbivory, and plant status. Both PE-MPs and herbivory significantly reduced the root mass fraction and root-to-shoot ratio (RSR) while increasing the shoot mass fraction, with the PE-MP-induced reduction in RSR being stronger in native plants. Our findings suggest that multiple anthropogenic stressors can act as ecological filters, reshaping plant competitive dynamics and accelerating community shifts toward stress-tolerant species.