The symbiosis between plants and arbuscular mycorrhizal (AM) fungi is integral to terrestrial ecosystem functioning. The vast majority of land plants associate with and provide carbon to these fungi, which in turn provide plants with increased access to soil minerals (especially phosphorous), making the symbiosis a vital player in global nutrient cycling. AM fungi can alter results of plant-plant competition and impact the levels of plant diversity supported in a community. AM fungi have also been discussed as critical components of conservation biology because their presence may be a necessary precursor for the restoration and maintenance of imperiled plant populations and AM fungi may also mediate exotic plant invasions. Despite the importance of this symbiosis, we have little understanding of such basic processes in this relationship as the degree of selectivity in the host-fungal interactions and how many AM fungal taxa comprise local and global communities. We surveyed the AM fungal community in the roots of 50 individual plants from nine common perennial plant species at an Oregon remnant bunchgrass prairie, described the AM fungal taxonomic diversity, and determined whether partner selectivity played a role in root AM fungal community composition.

Results/Conclusions

Phylogenetic analysis of AM fungal large subunit (LSU) ribosomal RNA gene sequences revealed at least 30 AM fungal taxa were present at the prairie, thirteen of which had no match in Genbank (based on >96% identity). Our new primers revealed a greater proportion of taxa in the orders Diversisporales and Archaeosporales compared to previous studies. We also assayed the 50 individual plants for presence of fifteen of the AM fungal taxa via PCR with primers specific to each taxon. Multivariate analysis with the presence/absence data indicates that associations between host species and the AMF in their roots were non-random and provides evidence for the existence of partner selection processes. The degree of selectivity in this symbiosis must be understood if AM fungi are to be effectively integrated into conservation strategies that will maintain plant diversity, promote endangered species, and protect against invasions by exotics.