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 phylogenetic analyses. A main portion (62.8%) of the OTUs belonged to Ascomycota, 32.0% to Basidiomycota, 3.9% to Chytridiomycota, 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 included two with high sequence similarity (>99%) to the agaric Entoloma conferendum (Britzelm.) Noordel and the endophyte 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 fungal diversity associated with boreal forest bryophytes that deserves further study.