title: Fungal partner shifts during the evolution of mycoheterotrophy in Neottia.
abstract: Few previous studies have examined how mycobionts change during the evolution from autotrophy to mycoheterotrophy based on phylogenetic hypotheses. Neottia (Orchidaceae) comprises leafy species that are autotrophic and related leafless mycoheterotrophic species, and the phylogenetic relationships among them have been clarified. Accordingly, Neottia is a suitable taxon for investigating the question above. Here we clarified the diversity of mycobionts in Neottia plants and elucidated changes in the character of symbiotic associations during the evolution of mycoheterotrophy.
  
  
  
  We sequenced the internal transcribed spacer (ITS) regions of nuclear ribosomal (nr) DNA for mycobionts of Neottia plants. Furthermore, we selected one representative DNA sample from each fungal operational taxonomic unit (OTU) and used it to amplify the large subunit (LSU) nrDNA sequences. Phylogenetic analyses of Sebacinales (basidiomycetes), the dominant mycobiont of Neottia, were conducted and sample-based rarefaction curves generated for the observed mycobiont richness on each OTU.
  
  
  
  Leafy and leafless species in Neottia were associated with Sebacinales Group B and Sebacinales Group A, respectively. The composition and specificity level of fungal partners varied among Neottia species.
  
  
  
  Fungal partner composition and specificity level changed with speciation in both leafy and leafless Neottia species. In particular, mycorrhizal associations likely shifted from Sebacinales Group B to Group A during the evolution from autotrophy to mycoheterotrophy. Partner shifts to Sebacinales Group A have also been reported in the evolution of mycoheterotrophy of other plant groups, suggesting that convergence to this fungal group occurs in association with the evolution of mycoheterotrophy.
authors.affiliation: Tsukuba Botanical Garden, National Museum of Nature and Science, 4-1-1, Amakubo, Tsukuba, Ibaraki 305-0005, Japan sebacina@gmail.com.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Yagame
authors.affiliation: Faculty of Agriculture, Saga University, 1 Honjo-machi, Saga 840-8502, Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Ogura-Tsujita
authors.affiliation: Tsukuba Botanical Garden, National Museum of Nature and Science, 4-1-1, Amakubo, Tsukuba, Ibaraki 305-0005, Japan.
authors.forename: Akihiko
authors.initials: A
authors.lastname: Kinoshita
authors.affiliation: Department of Natural and Environmental Science, Teikyo University of Science, 2525 Yatsusawa, Uenohara 409-0193, Japan.
authors.forename: Koji
authors.initials: K
authors.lastname: Iwase
authors.affiliation: Tsukuba Botanical Garden, National Museum of Nature and Science, 4-1-1, Amakubo, Tsukuba, Ibaraki 305-0005, Japan.
authors.forename: Tomohisa
authors.initials: T
authors.lastname: Yukawa
mesh_terms: D001487:Basidiomycota / Q000235:genetics / Q000502:physiology*; D005075:Biological Evolution; D004271:DNA, Fungal / Q000235:genetics; D004275:DNA, Ribosomal / Q000235:genetics; D021903:DNA, Ribosomal Spacer / Q000235:genetics; D038821:Mycorrhizae / Q000502:physiology; D029595:Orchidaceae / Q000382:microbiology*; D010802:Phylogeny; D013559:Symbiosis
chemical_list: D004271:DNA, Fungal; D004275:DNA, Ribosomal; D021903:DNA, Ribosomal Spacer
keywords: Orchidaceae; Sebacinales; ectomycorrhizal fungi; evolution; mycoheterotrophy; mycorrhizal symbiosis; saprophytic fungi; specificity