Two mycoheterotrophic orchids from Thailand tropical dipterocarpacean forests associate with a broad diversity of ectomycorrhizal fungi.
BACKGROUND
Mycoheterotrophic plants are considered to associate very specifically with fungi. Mycoheterotrophic orchids are mostly associated with ectomycorrhizal fungi in temperate regions, or with saprobes or parasites in tropical regions. Although most mycoheterotrophic orchids occur in the tropics, few studies have been devoted to them, and the main conclusions about their specificity have hitherto been drawn from their association with ectomycorrhizal fungi in temperate regions.


RESULTS
We investigated three Asiatic Neottieae species from ectomycorrhizal forests in Thailand. We found that all were associated with ectomycorrhizal fungi, such as Thelephoraceae, Russulaceae and Sebacinales. Based on 13C enrichment of their biomass, they probably received their organic carbon from these fungi, as do mycoheterotrophic Neottieae from temperate regions. Moreover, 13C enrichment suggested that some nearby green orchids received part of their carbon from fungi too. Nevertheless, two of the three orchids presented a unique feature for mycoheterotrophic plants: they were not specifically associated with a narrow clade of fungi. Some orchid individuals were even associated with up to nine different fungi.


CONCLUSIONS
Our results demonstrate that some green and mycoheterotrophic orchids in tropical regions can receive carbon from ectomycorrhizal fungi, and thus from trees. Our results reveal the absence of specificity in two mycoheterotrophic orchid-fungus associations in tropical regions, in contrast to most previous studies of mycoheterotrophic plants, which have been mainly focused on temperate orchids.
Roy
Mélanie
M
Centre d'Ecologie Fonctionnelle et Evolutive (CNRS, UMR 5175), Equipe Interactions Biotiques, Montpellier, France. melanie.roy@cefe.cnrs.fr
Watthana
Santi
S
Stier
Anna
A
Richard
Franck
F
Vessabutr
Suyanee
S
Selosse
Marc-André
MA
D002247:Carbon Isotopes / Q000032:analysis; D004271:DNA, Fungal / Q000737:chemistry*; D021903:DNA, Ribosomal Spacer / Q000032:analysis; D053958:Dipterocarpaceae; D004734:Energy Metabolism; D005638:Fruit / Q000737:chemistry; D005658:Fungi / Q000737:chemistry / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*; D038821:Mycorrhizae / Q000737:chemistry / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*; D009587:Nitrogen Isotopes / Q000032:analysis; D029595:Orchidaceae / Q000145:classification / Q000382:microbiology*; D010802:Phylogeny; D018515:Plant Leaves / Q000737:chemistry; D018517:Plant Roots / Q000382:microbiology*; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D013559:Symbiosis; D013785:Thailand; D014197:Trees; D014329:Tropical Climate
D002247:Carbon Isotopes; D004271:DNA, Fungal; D021903:DNA, Ribosomal Spacer; D009587:Nitrogen Isotopes
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