Two new species, Fomitopsis mounceae and F. schrenkii (Polyporales, Basidiomycota) in the F. pinicola species complex in North America, are described and illustrated. Previous molecular phylogenetic analyses identified three well-delimited lineages that represent F. mounceae and F. ochracea from Canada, the Appalachian Mountains, and the northern United States and F. schrenkii from western and southwestern regions of the United States. Fomitopsis pinicola sensu stricto is restricted to Eurasia and does not occur in North America. Morphological descriptions of basidiocarps and cultures for F. mounceae, F. schrenkii, and F. ochracea are presented. The three species are readily differentiated by nuc rDNA internal transcribed spacer (ITS1-5.8S-ITS2 = ITS) sequence, geographic distribution, and basidiospore size. Polyporus ponderosus H. Schrenk is an earlier illegitimate synonym of F. schrenkii. Both F. mounceae and F. schrenkii have a heterothallic multiallelic incompatibility system.
Keywords: 2 new taxa; Basidiomycota; Fomitopsidaceae; brown rot.