Sensitivity to AMF species is greater in late-successional than early-successional native or nonnative grassland plants

Sensitivity of plant species to individual arbuscular mycorrhizal (AM) fungal species is of primary importance to understanding the role of AM fungal diversity and composition in plant ecology. Currently, we do not have a predictive framework for understanding which plant species are sensitive to different AM fungal species. In two greenhouse studies, we tested for differences in plant sensitivity to different AM fungal species and mycorrhizal responsiveness across 17 grassland plant species of North America that varied in successional stage, native status, and plant family by growing plants with different AM fungal treatments including eight single AM fungal isolates, diverse mixtures of AM fungi, and non-inoculated controls. We found that late successional grassland plant species were highly responsive to AM fungi and exhibited stronger sensitivity in their response to individual AM fungal taxa compared to nonnative or early successional native grassland plant species. We confirmed these results using a meta-analysis that included 13 experiments, 37 plant species, and 40 fungal isolates (from nine publications and two greenhouse experiments presented herein). Mycorrhizal responsiveness and sensitivity of response (i.e., variation in plant biomass response to different AM fungal taxa) did not differ by the source of fungal inocula (i.e., local or not local) or plant family. Sensitivity of plant response to AM fungal species was consistently correlated with the average mycorrhizal response of that plant species. This study identifies that AM fungal identity is more important to the growth of late successional plant species than early successional or nonnative plant species, thereby predicting that AM fungal composition will be more important to plant community dynamics in late successional communities than in early successional or invaded plant communities.