Comparisons of AM fungal spore communities with the same hosts but different soil chemistries over local and geographic scales.

Arbuscular mycorrhizal (AM) fungi are ubiquitous and ecologically important microbes in grasslands. Both the host plant species and soil properties have been suggested as potentially important factors structuring AM fungal communities based on studies within local field sites. However, characterizations of the communities in relation to both host plant identity and soil properties in natural plant communities across both local and broader geographic scales are rare. We examined the AM fungal spore communities associated with the same C(4) grasses in two Eastern serpentine grasslands, where soils have elevated heavy metals, and two Iowa tallgrass prairie sites. We compared AM fungal spore communities among host plants within each site, looked for correlations between fungal communities and local soil properties, and then compared communities among sites. Spore communities did not vary with host plant species or correlate with local soil chemical properties at any site. They did not differ between the two serpentine sites or between the two prairie sites, despite geographic separation, but they did differ between serpentine and prairie. Soil characteristics are suggested as a driving force because spore communities were strongly correlated with soil properties when data from all four sites are considered, but climatic differences might also play a role.