Mycorrhizal preference promotes habitat invasion by a native Australian orchid: Microtis media

Ann Bot. 2013 Mar;111(3):409-18. doi: 10.1093/aob/mcs294. Epub 2012 Dec 28.


Background and aims: Mycorrhizal specialization has been shown to limit recruitment capacity in orchids, but an increasing number of orchids are being documented as invasive or weed-like. The reasons for this proliferation were examined by investigating mycorrhizal fungi and edaphic correlates of Microtis media, an Australian terrestrial orchid that is an aggressive ecosystem and horticultural weed.

Methods: Molecular identification of fungi cultivated from M. media pelotons, symbiotic in vitro M. media seed germination assays, ex situ fungal baiting of M. media and co-occurring orchid taxa (Caladenia arenicola, Pterostylis sanguinea and Diuris magnifica) and soil physical and chemical analyses were undertaken.

Key results: It was found that: (1) M. media associates with a broad taxonomic spectrum of mycobionts including Piriformospora indica, Sebacina vermifera, Tulasnella calospora and Ceratobasidium sp.; (2) germination efficacy of mycorrhizal isolates was greater for fungi isolated from plants in disturbed than in natural habitats; (3) a higher percentage of M. media seeds germinate than D. magnifica, P. sanguinea or C. arenicola seeds when incubated with soil from M. media roots; and (4) M. media-mycorrhizal fungal associations show an unusual breadth of habitat tolerance, especially for soil phosphorus (P) fertility.

Conclusions: The findings in M. media support the idea that invasive terrestrial orchids may associate with a diversity of fungi that are widespread and common, enhance seed germination in the host plant but not co-occurring orchid species and tolerate a range of habitats. These traits may provide the weedy orchid with a competitive advantage over co-occurring orchid species. If so, invasive orchids are likely to become more broadly distributed and increasingly colonize novel habitats.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptation, Physiological
  • Australia
  • Basidiomycota / classification
  • Basidiomycota / growth & development
  • Ecosystem*
  • Genetic Variation
  • Germination
  • Introduced Species
  • Mycorrhizae / classification
  • Mycorrhizae / growth & development*
  • Orchidaceae / growth & development
  • Orchidaceae / microbiology*
  • Phosphorus / chemistry
  • Phylogeny
  • Plant Roots / growth & development
  • Plant Roots / microbiology
  • Seeds / growth & development
  • Soil / chemistry
  • Soil Microbiology*
  • Symbiosis


  • Soil
  • Phosphorus