Host plant species effects on arbuscular mycorrhizal fungal communities intallgrass prairie

Symbiotic associations between plants and arbuscular mycorrhizal (AM) fungi are ubiquitous in many herbaceous plant communities and can have large eff ects on these communities and ecosystem processes. The extent of species-sp ecificity between these plant and fungal symbionts in nature is poorly know n, yet reciprocal effects of the composition of plant and soil microbe comm unities is an important assumption of recent theoretical models of plant: c ommunity structure. In grassland ecosystems, host plant, species may have a n important role in determining development and sporulation of AM fungi and patterns of fungal species composition and diversity. In this study, the e ffects of five different host plant species [Poa pratensis L., Sporobolus h eterolepis (A. Gray) A. Gray, Panicum virgatum L., Baptisia bracteata Muhl. ex Ell., Solidago missouriensis Nutt.] on spore communities of AM fungi in tallgrass prairie were examined. Spore abundances and species composition of fungal communities of soil samples collected from patches within tallgra ss prairie were significantly influenced by the host plant species that dom inated the patch. The AM fungal spore community associated with B. bracteat a showed the highest species diversity and the fungi associated with Pn. vi rgatum showed the lowest diversity. Results from sorghum trap cultures usin g soil collected from under different host plant species showed differentia l sporulations of AM fungal species. In addition, a greenhouse study was co nducted in which different host plant species were grown in similar tallgra ss prairie soil. After 4 months of growth, AM fungal species composition wa s significantly different beneath each host species. These results strongly suggest that AM fungi show some degree of host-specificity and are not ran domly distributed in tallgrass prairie. The demonstration that host plant s pecies composition influences AM fungal species composition provides suppor t for current feedback models predicting strong regulatory effects of soil communities on plant community structure. Differential responses of AM fung i to host plant species may also play an important role in the regulation o f species composition and diversity in AIM fungal communities.