Mycorrhizal fungi and distribution of specialized orchids

Specialized interactions have repeatedly evolved in the Orchidaceae, and subsequently may limit the geographic range of orchids. Davis et al. undertake a phylogenetic analysis of fungal isolates from Pheladenia deformis, an orchid with a continent-wide distribution, and find that the orchid is predominantly utilizing a single fungal operational taxonomic unit (OTU) in the genus Sebacina. The use of a widespread fungal OTU in P. deformis enables a broad distribution despite high mycorrhizal specificity. Other Sebacina OTUs utilized by different short-range endemic orchids were also found to have a continent-wide distribution, demonstrating that biogeographic patterns in orchids are likely to be driven by other factors such as edaphic requirements and pollinator-mediated limitations.