Evolution of nutritional modes of Ceratobasidiaceae (Cantharellales, Basidiomycota) as revealed from publicly available ITS sequences

• All nutritional modes were phylogenetically conserved in the Ceratobasidiaceae.
• Saprobes and orchid symbionts were phylogenetically homogeneous.
• Autotrophic orchids form root symbiosis with available isolates in soil.
• Ectomycorrhiza-forming capability has evolved twice within the Ceratobasidiaceae.

Fungi from the Ceratobasidiaceae family have important ecological roles as pathogens, saprotrophs, non-mycorrhizal endophytes, orchid mycorrhizal and ectomycorrhizal symbionts, but little is known about the distribution and evolution of these nutritional modes. All public ITS sequences of Ceratobasidiaceae were downloaded from databases, annotated with ecological and taxonomic metadata, and tested for the non-random phylogenetic distribution of nutritional modes. Phylogenetic analysis revealed six main clades within Ceratobasidiaceae and a poor correlation between molecular phylogeny and morphological–cytological characters traditionally used for taxonomy. Sequences derived from soil (representing putative saprotrophs) and orchid mycorrhiza clustered together, but remained distinct from pathogens. All nutritional modes were phylogenetically conserved in the Ceratobasidiaceae based on at least one index. Our analyses suggest that in general, autotrophic orchids form root symbiosis with available Ceratobasidiaceae isolates in soil. Ectomycorrhiza-forming capability has evolved twice within the Ceratobasidiaceae and it had a strong influence on the evolution of mycoheterotrophy and host specificity in certain orchid taxa.