How are plant and fungal communities linked to each other in belowground ecosystems?: community-wide analysis of the partner preference of root-associated fungi and their host plants. rhizosphere metagenome

In natural forests, hundreds or more of fungi colonize plant roots. In the symbiosis, preference for partners is the key to understand how the community structures of root-associated fungi and their host plants influence each other. In an oak-dominated forest in Japan, we investigated the root-associated fungal community based on pyrosequencing analysis of the roots of 33 plant species. Of the observed 387 fungal taxa, 153 [39.5%] were detected from at least two plant species. Albeit the sharing of many mycorrhizal and root-endophytic fungi, the five most-common plant species in the community had statistically-significant preference for fungal taxa. Likewise, fungi had remarkable variation in host preference even within the same phylogenetic or ecological groups. For instance, some fungi in the ectomycorrhizal-fungal family Russulaceae showed host preference for specific oak (Quercus) species, while other Russulaceae fungi were found even from ``non-ectomycorrhizal'' plants (e.g., Lyonia and Ilex). Putatively-endophytic ascomycetes in the orders Helotiales and Chaetothyriales showed variation in host preference, too, and many of them were shared among plant species as major symbionts. Overall, this study suggested that the entire stricture of belowground plant-fungal symbiosis is ideally described by continuity spanning random sharing of hosts/symbionts to complete compartmentalization by mycorrhizal type.