title: The importance of associations with saprotrophic non-Rhizoctonia fungi among fully mycoheterotrophic orchids is currently under-estimated: novel evidence from sub-tropical Asia.
abstract: OBJECTIVE
  Most fully mycoheterotrophic (MH) orchids investigated to date are mycorrhizal with fungi that simultaneously form ectomycorrhizas with forest trees. Only a few MH orchids are currently known to be mycorrhizal with saprotrophic, mostly wood-decomposing, fungi instead of ectomycorrhizal fungi. This study provides evidence that the importance of associations between MH orchids and saprotrophic non-Rhizoctonia fungi is currently under-estimated.
  
  
  METHODS
  Using microscopic techniques and molecular approaches, mycorrhizal fungi were localized and identified for seven MH orchid species from four genera and two subfamilies, Vanilloideae and Epidendroideae, growing in four humid and warm sub-tropical forests in Taiwan. Carbon and nitrogen stable isotope natural abundances of MH orchids and autotrophic reference plants were used in order to elucidate the nutritional resources utilized by the orchids.
  
  
  RESULTS
  Six out of the seven MH orchid species were mycorrhizal with either wood- or litter-decaying saprotrophic fungi. Only one orchid species was associated with ectomycorrhizal fungi. Stable isotope abundance patterns showed significant distinctions between orchids mycorrhizal with the three groups of fungal hosts.
  
  
  CONCLUSIONS
  Mycoheterotrophic orchids utilizing saprotrophic non-Rhizoctonia fungi as a carbon and nutrient source are clearly more frequent than hitherto assumed. On the basis of this kind of nutrition, orchids can thrive in deeply shaded, light-limiting forest understoreys even without support from ectomycorrhizal fungi. Sub-tropical East Asia appears to be a hotspot for orchids mycorrhizal with saprotrophic non-Rhizoctonia fungi.
authors.affiliation: Biology Department, National Museum of Natural Science, No 1, Kuan-Chien Rd, Taichung, Taiwan, Department of Life Sciences, National Chung Hsing University, Taichung 40227, Taiwan.
authors.forename: Yung-I
authors.initials: YI
authors.lastname: Lee
authors.affiliation: The Experimental Forest, College of Bio-Resources and Agriculture, National Taiwan University, 12 Chienshan Rd., Sec. 1, Chushan Township, Nantou 55750, Taiwan, Department of Life Science, National Taiwan Normal University, 88 Tingchow Rd., Sec. 4, Taipei 11677, Taiwan and.
authors.forename: Chih-Kai
authors.initials: CK
authors.lastname: Yang
authors.affiliation: Laboratory of Isotope Biogeochemistry, Bayreuth Center of Ecology and Environmental Research (BayCEER), University of Bayreuth, D-95440 Bayreuth, Germany gerhard.gebauer@uni-bayreuth.de.
authors.forename: Gerhard
authors.initials: G
authors.lastname: Gebauer
mesh_terms: D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D038821:Mycorrhizae / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D029595:Orchidaceae / Q000254:growth & development / Q000502:physiology*; D010802:Phylogeny; D017422:Sequence Analysis, DNA; D013624:Taiwan
chemical_list: D005656:Fungal Proteins
keywords: Epidendroideae; Gastrodia; Orchidaceae; Orchids; Vanilloideae; carbon; ectomycorrhiza; mycoheterotrophy; mycorrhiza; nitrogen; saprotrophic fungi.; stable isotopes