title: Independent recruitment of saprotrophic fungi as mycorrhizal partners by tropical achlorophyllous orchids.
abstract: Mycoheterotrophic orchids have adapted to shaded forest understory by shifting to achlorophylly and receiving carbon from their mycorrhizal fungi. In temperate forests, they associate in a highly specific way with fungi forming ectomycorrhizas on nearby trees, and exploiting tree photosynthates. However, many rainforests lack ectomycorrhizal fungi, and there is evidence that some tropical Asiatic species associate with saprotrophic fungi. To investigate this in different geographic and phylogenetic contexts, we identified the mycorrhizal fungi supporting two tropical mycoheterotrophic orchids from Mascarene (Indian Ocean) and Caribbean islands. We tested their possible carbon sources by measuring natural nitrogen ((15)N) and carbon ((13)C) abundances. Saprotrophic basidiomycetes were found: Gastrodia similis associates with a wood-decaying Resinicium (Hymenochaetales); Wullschlaegelia aphylla associates with both litter-decaying Gymnopus and Mycena species, whose rhizomorphs link orchid roots to leaf litter. The (15)N and (13)C abundances make plausible food chains from dead wood to G. similis and from dead leaves to W. aphylla. We propose that temperature and moisture in rainforests, but not in most temperate forests, may favour sufficient saprotrophic activity to support development of mycoheterotrophs. By enlarging the spectrum of mycorrhizal fungi and the level of specificity in mycoheterotrophic orchids, this study provides new insights on orchid and mycorrhizal biology in the tropics.
authors.affiliation: Centre d'Ecologie Fonctionnelle et Evolutive (CNRS, UMR 5175), Equipe Interactions Biotiques, 1919 Route de Mende, F-34293 Montpellier cedex 5, France.|UMR C53 Peuplements Végétaux et Bioagresseurs en Milieu Tropical, Université de La Réunion, 15 Avenue René Cassin, BP 7151, F-97715 Saint-Denis cedex 9, France.
authors.forename: Florent
authors.initials: F
authors.lastname: Martos
authors.affiliation: Conservatoire Botanique des Antilles Françaises, F-97100 Basse Terre, Guadeloupe, France.|EA 926 DYNECAR, Université des Antilles et de la Guyane, BP 592, F-97159 Pointe-à-Pitre, Guadeloupe, France.
authors.forename: Maguy
authors.initials: M
authors.lastname: Dulormne
authors.affiliation: UMR C53 Peuplements Végétaux et Bioagresseurs en Milieu Tropical, Université de La Réunion, 15 Avenue René Cassin, BP 7151, F-97715 Saint-Denis cedex 9, France.
authors.forename: Thierry
authors.initials: T
authors.lastname: Pailler
authors.affiliation: Dipartimento di Biologia Vegetale dell'Università, Istituto per la Protezione delle Piante - CNR, Viale Mattioli 25, I-10125 Torino, Italy.
authors.forename: Paola
authors.initials: P
authors.lastname: Bonfante
authors.affiliation: Dipartimento di Biologia Vegetale dell'Università, Istituto per la Protezione delle Piante - CNR, Viale Mattioli 25, I-10125 Torino, Italy.
authors.forename: Antonella
authors.initials: A
authors.lastname: Faccio
authors.affiliation: UMR C53 Peuplements Végétaux et Bioagresseurs en Milieu Tropical, Université de La Réunion, 15 Avenue René Cassin, BP 7151, F-97715 Saint-Denis cedex 9, France.
authors.forename: Jacques
authors.initials: J
authors.lastname: Fournel
authors.affiliation: Centre d'Ecologie Fonctionnelle et Evolutive (CNRS, UMR 5175), Equipe Interactions Biotiques, 1919 Route de Mende, F-34293 Montpellier cedex 5, France.
authors.forename: Marie-Pierre
authors.initials: MP
authors.lastname: Dubois
authors.affiliation: Centre d'Ecologie Fonctionnelle et Evolutive (CNRS, UMR 5175), Equipe Interactions Biotiques, 1919 Route de Mende, F-34293 Montpellier cedex 5, France.
authors.forename: Marc-André
authors.initials: MA
authors.lastname: Selosse
mesh_terms: D001487:Basidiomycota / Q000145:classification / Q000235:genetics / Q000502:physiology; D002247:Carbon Isotopes; D002980:Climate; D020387:Food Chain; D038821:Mycorrhizae / Q000145:classification / Q000235:genetics / Q000502:physiology*; D009587:Nitrogen Isotopes; D029595:Orchidaceae / Q000382:microbiology*; D010802:Phylogeny; D013559:Symbiosis / Q000235:genetics / Q000502:physiology; D014329:Tropical Climate
chemical_list: D002247:Carbon Isotopes; D009587:Nitrogen Isotopes
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