Taxonomic and functional diversity of AM fungi in serpentine and prairie grasslands

Diversity and functioning are the most important topics in the ecology of arbuscular mycorrhizal (AM) fungi. To address what ecological factors determine the species composition of an AM fungal community and what functional consequences different AM fungal communities have on particular plant-soil systems, my dissertation research examines the species composition and functioning of AM fungal communities associated with the same C4 grasses common to Eastern serpentine grasslands and Mid-west tall-grass prairies. In the first chapter, I compare the natural AM fungal community compositions between serpentine grasslands and prairies. Distinct AM fungal communities were revealed in the two types of grasslands, and there was a noticeable correlation between soil properties and fungal communities. Chapter two describes an experiment aiming to test the hypothesis that the local AM fungal communities are better suited to promoting plant growth in that particular soil environment than are AM fungal communities from a different soil environment. In both serpentine and prairie soils, the degree of benefit to Sorghastrum growth provided by the native AM fungal community was always significantly higher than that provided by the foreign community, suggesting that AM fungi and soil are ecologically matched. In Chapter three, I address whether host-specificity exists in community and population levels of arbuscular mycorrhizae through analyzing the spore data collected from the field and greenhouse experiments. Little host-specificity was demonstrated, however, functional difference was observed between AM roots of two different grass species inoculated with the same spore community. Functional difference driven by host identity could have important ecological consequences. My final chapter evaluates the functional difference among populations of the single fungal species associated with various host plant species in the same serpentine grassland. Spores of Gi. gigantea collected on three different host plant species in the field exhibited significantly different effects on the growth of one of the host plants under the identical greenhouse conditions. This is the first report on the intraspecific variation driven by host plant species, and future investigations are needed in order to fully uncover its underlying causes and ecological consequences