Intraspecific variation in an arbuscular mycorrhizal fungus affects a plant and an AMF community.

Arbuscular mycorrhizal fungi (AMF) show substantial genetic, trait, and functional variation within species. Whether this intraspecific variability has community-level consequences for plant and AMF communities is unclear. This study investigated whether introduced conspecific AMF affected a resident AMF and plant community. Mesocosms containing natural soils and a mixed plant community were inoculated with three conspecific isolates of Rhizophagus irregularis and grown for 17 wk. We measured AMF isolate abundance, plant performance (aboveground biomass, foliar phosphorus, seed production), and plant and AMF community response (diversity and composition). AMF isolate identity affected AMF isolate abundance though effects varied with host identity. Isolate identity affected aboveground biomass of two host species. A small shift in plant community composition, but not diversity, occurred between two isolate treatments. The most abundant isolate affected turnover of rare AMF taxa in the soil community but did not alter the dominant AMF community. Whether small community shifts would compound or stabilize over time remains to be seen. Given the growing use of AMF-based agricultural and forestry products, often represented by a single genetic isolate, there is a pressing need to understand how intraspecific AMF variation fits within ecological frameworks.