Invasive plant species have been shown to be able to alter indigenous arbuscular mycorrhizal (AM) fungal community, but the underlying mechanisms and resulting consequences are not well understood. Using both morphological and molecular methods, we conducted three experiments to investigate how a highly invasive forb, Solidago canadensis L. (goldenrods), affects the structure of soil AM fungal community and how the resulting alteration influences the N acquisition and growth of S. canadensis L. and the native forb Kummerowia striata (Thunb.) Schindl. We first examined the AM fungal community in field site under K. striata and S. canadensis L. for consecutive three years. Then, we experimentally created an AM fungal community with five species and examined the divergence of the constructed AM fungal community under invasive S. canadensis and native K. striata after two growing seasons. Also, the host specificity of the fungi was assessed.
Results/Conclusions Invasion by S. canadensis L. significantly altered the AM fungal spore composition in field soil by increasing spore density of Glomus geosporum but reducing original dominant species Glomus mosseae. S. canadensis invasion also reduced the relative abundance of G. mosseae colonized in roots of native K. striata. After two growing seasons, the constructed AM fungal community diverged, with G. geosporum being dominant under S. canadensis L. and G. mosseae occupied under K. striata. Among the five AM fungal species, G. geosporum was most effective in enhancing 15N acquisition for S. canadensis but G. mosseae was for K. striata. Both invasive S. canadensis and native K. striata showed strong AM fungal mycorrhizal dependence, with S. canadensis most responsive to G. geosporum and K. striata to G. mosseae. These results suggest that host specificity may be an important mechanism through which mycorrhizae modulate plant invasion.
