Marchandiomyces lignicola sp. nov. shows recent and repeated transition between a lignicolous and a lichenicolous habit.

The anamorphic basidiomycete genus Marchandiomyces presently includes two common lichenicolous (lichen-inhabiting) species, M. corallinus and M. aurantiacus (teleomorph Marchandiobasidium aurantiacum). We describe here a new species, M. lignicola sp. nov., that is similar to M. corallinus in the colour of its sclerotia, but differs in having a wood-inhabiting (lignicolous) habit. The phylogenetic position of this lignicolous fungus was compared with the lichenicolous species of Marchandiomyces and related species currently placed in the basidiomycetous families Corticiaceae and Ceratobasidiaceae using parsimony, likelihood, and Bayesian analyses of complete sequences of the nuclear small subunit and internal transcribed spacers ribosomal DNA, and a portion of the nuclear large subunit ribosomal DNA. These DNA sequences were obtained from isolated cultures of freshly collected specimens. Significant Bayesian posterior probabilities, as well as maximum likelihood and parsimony analyses, indicate that the new lignicolous species is closely related to M. corallinus, the type species of Marchandiomyces. In most analyses these two species are monophyletic with the lichenicolous M. aurantiacus, although this relationship is not strongly supported. Since M. lignicola is more closely related to M. corallinus than to M. aurantiacus, either a transition to the lignicolous habit occurred recently within an ancestral lichenicolous group or, more likely, transition to the lichenicolous habit arose recently and in parallel from an ancestral lignicolous habit.