Mycorrhizal species identity affects plant community structure and invasion: a microcosm study

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Abstract
Previous studies have shown that arbuscular mycorrhizal fungi (AMF) can mediate plant interactions, thereby affecting plant community structure. Little is known, however, about whether the presence of different AMF species leads to differences in plant community structure or invasion success by introduced species. To investigate the effects of AMF species on community structure and invasion, we created replicate microcosms containing soil inoculated with one of three different AMF species (Glomus spurcumPfeiffer, Walker & Bloss,Scutellospora erythropa(Koske & Walker) Walker & Sanders, orScutellospora verrucosa(Koske & Walker) Walker & Sanders) or a mixture of all three AMF species. Seeds of seven naturally co‐occurring plant species (Ageratum conyzoidesL.,Cyperus compressusL.,Chamaecrista nictitans(L.),Crotalaria incanaL.,Hyptis pectinata(L.) Poit.,Sida rhombifoliaL.,Melinis repens(Willd.) Zizka) in Hawai‘i were sown equally into these microcosms, which were placed on outdoor benches. Plant community development was monitored over a season. Mid‐way through the experiment, an invader (Bidens pilosaL.) was added to the established communities to determine whether mycorrhizal species identity affected invasion success. Final aboveground and belowground phytomass were used to assess plant community differences among treatments. Although the identity of the dominant plant species (Melinis repens) remained the same in all treatments, community dominance, community productivity, plant species richness, Shannon index of diversity, and invasion success all varied with AMF species identity. Invasion success was not inversely related to species richness or diversity. Instead, increased richness, diversity, and invasion success all appeared to be related to decreased dominance byM. repensin the presence of certain AMF species. These results indicate that the composition of the AMF community belowground can influence the structure of the plant community aboveground, and may play a role in facilitating or repelling invasion.