title: Fine-scale spatial distribution of orchid mycorrhizal fungi in the soil of host-rich grasslands.
abstract: Mycorrhizal fungi are essential for the survival of orchid seedlings under natural conditions. The distribution of these fungi in soil can constrain the establishment and resulting spatial arrangement of orchids at the local scale, but the actual extent of occurrence and spatial patterns of orchid mycorrhizal (OrM) fungi in soil remain largely unknown. We addressed the fine-scale spatial distribution of OrM fungi in two orchid-rich Mediterranean grasslands by means of high-throughput sequencing of fungal ITS2 amplicons, obtained from soil samples collected either directly beneath or at a distance from adult Anacamptis morio and Ophrys sphegodes plants. Like ectomycorrhizal and arbuscular mycobionts, OrM fungi (tulasnelloid, ceratobasidioid, sebacinoid and pezizoid fungi) exhibited significant horizontal spatial autocorrelation in soil. However, OrM fungal read numbers did not correlate with distance from adult orchid plants, and several of these fungi were extremely sporadic or undetected even in the soil samples containing the orchid roots. Orchid mycorrhizal 'rhizoctonias' are commonly regarded as unspecialized saprotrophs. The sporadic occurrence of mycobionts of grassland orchids in host-rich stands questions the view of these mycorrhizal fungi as capable of sustained growth in soil.
authors.affiliation: Department of Life Sciences and Systems Biology, University of Torino, Viale Mattioli 25, 10125, Torino, Italy.
authors.forename: Samuele
authors.initials: S
authors.lastname: Voyron
authors.affiliation: Department of Life Sciences and Systems Biology, University of Torino, Viale Mattioli 25, 10125, Torino, Italy.
authors.forename: Enrico
authors.initials: E
authors.lastname: Ercole
authors.affiliation: CNR-Istituto per la Protezione Sostenibile delle Piante, UOS Turin (CNR-IPSP), Viale Mattioli 25, 10125, Torino, Italy.
authors.forename: Stefano
authors.identifier: http://orcid.org/0000-0002-2033-2286
authors.initials: S
authors.lastname: Ghignone
authors.affiliation: Department of Life Sciences and Systems Biology, University of Torino, Viale Mattioli 25, 10125, Torino, Italy.|CNR-Istituto per la Protezione Sostenibile delle Piante, UOS Turin (CNR-IPSP), Viale Mattioli 25, 10125, Torino, Italy.
authors.forename: Silvia
authors.initials: S
authors.lastname: Perotto
authors.affiliation: Department of Life Sciences and Systems Biology, University of Torino, Viale Mattioli 25, 10125, Torino, Italy.|CNR-Istituto per la Protezione Sostenibile delle Piante, UOS Turin (CNR-IPSP), Viale Mattioli 25, 10125, Torino, Italy.
authors.forename: Mariangela
authors.initials: M
authors.lastname: Girlanda
mesh_terms: D044822:Biodiversity; D005658:Fungi / Q000502:physiology*; D065948:Grassland; D038821:Mycorrhizae / Q000502:physiology*; D029595:Orchidaceae / Q000382:microbiology*; D018517:Plant Roots / Q000382:microbiology; D012988:Soil Microbiology; D013045:Species Specificity
keywords: 
  Tulasnella calospora
  ; Ceratobasidiaceae; Orchidaceae; Pezizaceae; Sebacinales; Serendipitaceae; Tulasnellaceae; fungal communities