title: Variation in nutrient-acquisition patterns by mycorrhizal fungi of rare and common orchids explains diversification in a global biodiversity hotspot.
abstract: OBJECTIVE
  Many terrestrial orchids have an obligate requirement for mycorrhizal associations to provide nutritional support from germination to establishment. This study will investigate the ability of orchid mycorrhizal fungi (OMF) to utilize a variety of nutrient sources in the nutrient-impoverished (low organic) soils of the Southwest Australian Floristic Region (SWAFR) in order to effectively compete, survive and sustain the orchid host.
  
  
  METHODS
  Mycorrhizal fungi representing key OMF genera were isolated from three common and widespread species: Pterostylis recurva, Caladenia flava and Diuris corymbosa, and one rare and restricted species: Drakaea elastica. The accessibility of specific nutrients was assessed by comparing growth including dry biomass of OMF in vitro on basal CN MMN liquid media.
  
  
  RESULTS
  Each of the OMF accessed and effectively utilized a wide variety of nutrient compounds, including carbon (C) sources, inorganic and organic nitrogen (N) and inorganic and organic phosphorus (P). The nutrient compounds utilized varied between the genera of OMF, most notably sources of N.
  
  
  CONCLUSIONS
  These results suggest that OMF can differentiate between niches (micro-niche specialization) in a constrained, highly resource-limited environment such as the SWAFR. Phosphorus is the most limited macronutrient in SWAFR soils and the ability to access phytate by OMF indicates a characterizing functional capacity of OMF from the SWAFR. Furthermore, compared with OMF isolated from the rare D. elastica, OMF associating with the common P. recurva produced far greater biomass over a wider variety of nutritional sources. This suggests a broader tolerance for habitat variation providing more opportunities for the common orchid for recruitment and establishment at a site.
authors.affiliation: School of Plant Biology, Faculty of Science, The University of Western Australia, Crawley, WA 6009, Australia.
authors.forename: Siti
authors.initials: S
authors.lastname: Nurfadilah
authors.forename: Nigel D
authors.initials: ND
authors.lastname: Swarts
authors.forename: Kingsley W
authors.initials: KW
authors.lastname: Dixon
authors.forename: Hans
authors.initials: H
authors.lastname: Lambers
authors.forename: David J
authors.initials: DJ
authors.lastname: Merritt
mesh_terms: D044822:Biodiversity; D050260:Carbohydrate Metabolism; D038821:Mycorrhizae / Q000378:metabolism*; D017672:Nitrogen Compounds / Q000378:metabolism; D029595:Orchidaceae / Q000382:microbiology*; D017553:Phosphorus Compounds / Q000378:metabolism; D013045:Species Specificity; D014904:Western Australia
chemical_list: D017672:Nitrogen Compounds; D017553:Phosphorus Compounds
keywords: Carbon; Ceratobasidium; Sebacina; Tulasnella; nitrogen; nutrients; orchid mycorrhizal fungi; phosphorus; soil; terrestrial orchid