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.
Belinda J. Davis, Ryan D. Phillips, Magali Wright, Celeste C. Linde, Kingsley W. Dixon, 2015, 'Continent-wide distribution in mycorrhizal fungi: implications for the biogeography of specialized orchids', Annals of Botany, vol. 116, no. 3, pp. 413-421 http://dx.doi.org/10.1093/aob/mcv084