Species richness promotes plant productivity by suppressing plant antagonists

Abstract The diversity-productivity relationship predicts a positive effect of plant species richness on primary productivity. One key mechanism predicted to underlie this relationship is the effect of plant diversity on the suppression of plant antagonists, including invertebrate herbivores, plant diseases, antagonistic plants in an agricultural context (i.e., weeds), root-feeding nematodes, or plant-consuming rodents. Here, we conduct a global meta-analysis from 609 biodiversity manipulation studies and complementary path analyses, and show that increasing plant species richness promotes plant productivity by decreasing plant antagonist pressure in terrestrial ecosystems (especially in agroecosystems), with similar patterns seen for herbaceous and woody plants as well as in tropical and temperate zones. These results demonstrate how a key mechanism underpinning the diversity-productivity relationship can be explained via weakened effects of antagonists on plant productivity. Our findings provide new evidence supporting a multitrophic diversity-productivity relationship and highlight the importance of maintaining species diversity to promote productivity as an ecosystem function in both agricultural and more natural systems.