High diversity of fungi associated with living parts of boreal forest bryophytes

Bryophytes are a dominant and functionally important component of the forest floor vegetation in boreal forests, yet little is known about the fungal diversity associated with these abundant plants. Using molecular identification, we document an ecologically and phylogenetically diverse array of fungi associated with the living parts of three widespread and abundant boreal forest bryophytes, i.e., Hylocomium splendens (Hedw.) Schimp. in B.S.G. , Pleurozium schreberi (Brid.) Mitt. , and Polytrichum commune Hedw. From 376 cloned ITS sequences, 158 operational taxonomic units (OTUs), roughly corresponding to the number of species, were defined based on sequence similarity searches (Fasta) and phyloge- netic analyses. A main portion (62.8%) of the OTUs belonged to Ascomycota, 32.0% to Basidiomycota, 3.9% to Chytri- diomycota, and 1.3% to Glomeromycota. The most common orders were Helotiales (18.6%), Agaricales (11.5%), Chaetothyriales (9.6%), and Tremellales (9.0%). Frequently detected OTUs of potentially high ecologic importance in- cluded two with high sequence similarity (>99%) to the agaric Entoloma conferendum (Britzelm.) Noordel and the endo- phyte Lophodermium piceae (Fckl.) Hoehn. , and various OTUs with affinity to the Helotian genus Hyphodiscus. Several ectomycorrhiza-forming basidiomycetes were also detected. Most OTUs (77.2%) were only detected once and a very small overlap in composition of OTUs was observed among the three bryophytes, indicating the occurrence of an immense fun- gal diversity associated with boreal forest bryophytes that deserves further study. l'aide de l'identification moleculaire, les auteurs ont etudieun ensemble ecologiquement et phylogenetiquement diversifie ´ de champignons associes aux parties vivantes de trois bryophytes abondantes et largement distribuees dans la foret boreale, soient les Hylocomium splendens (Hedw.) Schimp. in B.S.G. , Pleurozium schreberi (Brid.) Mitt. et Polytrichum commune Hedw. Apartir de 376 sequences ITS clonees et en appliquant des recherches de similaritede sequences (Fasta) et des analyses phylogenetiques, les auteurs ont defini 158 unites taxonomiques operationnelles (OTU's) correspondant en gros au nombre d'especes. La majorite ´ (62,8 %) des OTU's appartiennent aux Ascomycota, 32,0 % aux Basidiomycota, 3,9 % aux Chytridiomycota et 1,3 % aux Glomeromycota. Les Helotiales (18,6 %, les Agaricales (11,5 %), les Chaetothyriales (9,6 %) et les Tremellales, constituent les principaux ordres. Parmi les OTU's de grande importance ecologique frequem- ment reperes on en retrouve deux avec forte ressemblance de sequences (>99 %) avec l'agaric Entoloma conferendum (Britzelm.) Noordel et l'endophyte Lophodermium piceae (Fckl.) Hoehn. , ainsi que divers OTU's ayant des affinites avec les Helotiales du genre Hyphodiscus. On retrouve egalement plusieurs basidiomycetes mycorhiziens. La plupart des OTU's n'apparaissent qu'une seule fois (72,2 %) et on observe un tres faible recouvrement des OTU's pour l'ensemble des trois bryophytes, ce qui indique le besoin de poursuivre les etudes sur l'immense diversitefongique associee aux bryophytes de la foret boreale. Mots-cles: bryophytes, foret boreale, endophytes, echantillon environnemental, sequence rARN ITS, mousse.