title: Continent-wide distribution in mycorrhizal fungi: implications for the biogeography of specialized orchids.
abstract: OBJECTIVE
  Although mycorrhizal associations are predominantly generalist, specialized mycorrhizal interactions have repeatedly evolved in Orchidaceae, suggesting a potential role in limiting the geographical range of orchid species. In particular, the Australian orchid flora is characterized by high mycorrhizal specialization and short-range endemism. This study investigates the mycorrhizae used by Pheladenia deformis, one of the few orchid species to occur across the Australian continent. Specifically, it examines whether P. deformis is widely distributed through using multiple fungi or a single widespread fungus, and if the fungi used by Australian orchids are widespread at the continental scale.
  
  
  METHODS
  Mycorrhizal fungi were isolated from P. deformis populations in eastern and western Australia. Germination trials using seed from western Australian populations were conducted to test if these fungi supported germination, regardless of the region in which they occurred. A phylogenetic analysis was undertaken using isolates from P. deformis and other Australian orchids that use the genus Sebacina to test for the occurrence of operational taxonomic units (OTUs) in eastern and western Australia.
  
  
  RESULTS
  With the exception of one isolate, all fungi used by P. deformis belonged to a single fungal OTU of Sebacina. Fungal isolates from eastern and western Australia supported germination of P. deformis. A phylogenetic analysis of Australian Sebacina revealed that all of the OTUs that had been well sampled occurred on both sides of the continent.
  
  
  CONCLUSIONS
  The use of a widespread fungal OTU in P. deformis enables a broad distribution despite high mycorrhizal specificity. The Sebacina OTUs that are used by a range of Australian orchids occur on both sides of the continent, demonstrating that the short-range endemism prevalent in the orchids is not driven by fungal species with narrow distributions. Alternatively, a combination of specific edaphic requirements and a high incidence of pollination by sexual deception may explain biogeographic patterns in southern Australian orchids.
authors.affiliation: Kings Park and Botanic Garden, West Perth, 6005, Western Australia, School of Plant Biology, The University of Western Australia, Nedlands, 6009, Western Australia, Belinda.Newman@uwa.edu.au.
authors.forename: Belinda J
authors.initials: BJ
authors.lastname: Davis
authors.affiliation: Kings Park and Botanic Garden, West Perth, 6005, Western Australia.
authors.forename: Ryan D
authors.initials: RD
authors.lastname: Phillips
authors.affiliation: Graduate School of Land and Environment, The University of Melbourne, Burnley Campus, Richmond, Victoria 3121, Australia.
authors.forename: Magali
authors.initials: M
authors.lastname: Wright
authors.affiliation: Evolution, Ecology and Genetics, Research School of Biology, The Australian National University, Canberra, Australian Capital Territory 2601, Australia and.
authors.forename: Celeste C
authors.initials: CC
authors.lastname: Linde
authors.affiliation: Kings Park and Botanic Garden, West Perth, 6005, Western Australia, School of Plant Biology, The University of Western Australia, Nedlands, 6009, Western Australia.
authors.forename: Kingsley W
authors.initials: KW
authors.lastname: Dixon
mesh_terms: D005656:Fungal Proteins / Q000235:genetics; D018525:Germination; D038821:Mycorrhizae / Q000235:genetics / Q000502:physiology*; D029595:Orchidaceae / Q000254:growth & development / Q000382:microbiology* / Q000502:physiology*; D010802:Phylogeny; D063148:Plant Dispersal; D017422:Sequence Analysis, DNA; D013045:Species Specificity
chemical_list: D005656:Fungal Proteins
keywords: Australia; Orchidaceae; Pheladenia deformis; Sebacina; biogeography; fungi; mycorrhizae; specialized; symbiosis