title: A narrow group of monophyletic Tulasnella (Tulasnellaceae) symbiont lineages are associated with multiple species of Chiloglottis (Orchidaceae): Implications for orchid diversity.
abstract: OBJECTIVE
  The Orchidaceae is characterized by exceptional species diversity. Obligate orchid mycorrhizae are predicted to determine orchid distributions, and highly specific relationships between orchids and fungi may drive orchid diversification. In this study, mycorrhizal diversity was examined in the terrestrial, photosynthetic orchid genus Chiloglottis to test the hypothesis of mycorrhizal-mediated diversification in the genus Chiloglottis. This orchid genus secures pollination by sexual deception, an obligate and highly specific pollination strategy. Here we asked whether the obligate orchid-fungal interactions are also specific. •
  
  
  METHODS
  Two sequenced loci, the internal transcribed spacer region (ITS) and mitochondrial large subunit (mtLSU), were used to identify fungal isolates and assess fungal species diversity. Symbiotic germination of two species Chiloglottis aff. jeanesii and C. valida were used to assess germination potential of isolates and confirm mycorrhizal association. •
  
  
  RESULTS
  Phylogenetic analyses revealed that six representative Chiloglottis species spanning a broad survey of the genus were all associated with a narrow group of monophyletic Tulasnella fungal lineages. •
  
  
  CONCLUSIONS
  The Chiloglottis-Tulasnella interaction appears to be the first known case of such a narrow symbiont association across a broadly surveyed orchid genus. It appears that the specific pollination system of Chiloglottis, rather than specific orchid-fungal interactions has been the key driving force in the diversification of the genus. These findings also indicate that plant groups with highly specific mycorrhizal partners can have a widespread distribution.
authors: Evolution, Ecology and Genetics, Research School of Biology, 116 Daley Road, The Australian National University, Canberra, ACT 0200, Australia.
authors: Sean A
authors: SA
authors: Roche
authors: Richard J
authors: RJ
authors: Carter
authors: Rod
authors: R
authors: Peakall
authors: Leon M
authors: LM
authors: Smith
authors: Michael R
authors: MR
authors: Whitehead
authors: Celeste C
authors: CC
authors: Linde