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A systematic reevaluation of North American pyrophilous or “burn-loving” species of Pholiota is presented based on molecular and morphological examination of type and historical collections. Confusion surrounds application of the names P. brunnescens, P. carbonaria, P. castanea, P. fulvozonata, P. highlandensis, P. molesta, and P. subsaponacea, with multiple names applied to a single species and multiple species described more than once. Molecular annotations using nuc rDNA ITS1-5.8S-ITS2 (internal transcribed spacer [ITS] barcode) and RPB2 (RNA polymerase II second largest subunit) are used to aid in application of these names in a phylogenetic context. Based on ITS molecular annotations of 13 types, the following heterotypic synonymies are proposed: P. highlandensis (syn. P. carbonaria and P. fulvozonata); P. molesta (syn. P. subsaponacea); and P. brunnescens (syn. P. luteobadia). In addition, we observed that the species P. castanea, known previously only from the type collection in Tennessee, is found commonly on burned sites near the Gulf Coast and other southeast regions of the United States. Overall, the pyrophilous trait is evolutionarily derived in Pholiota. Endophytic and endolichenic stages were deduced for P. highlandensis, the most widely distributed of the pyrophilous Pholiota. As a result, we introduce the “body snatchers” hypothesis that explains the maintenance of some pyrophilous fungi in ecosystems as endophytes and/or endolichenic fungi. Photographs, taxonomic descriptions, and a dichotomous key to pyrophilous species of Pholiota that occur in North America are presented. 

ABSTRACT True fungi (Fungi) and fungus-like organisms (e.g.Mycetozoa,Oomycota) constitute the second largest group of organisms based on global richness estimates, with around 3 million predicted species. Compared to plants and animals, fungi have simple body plans with often morphologically and ecologically obscure structures. This poses challenges for accurate and precise identifications. Here we provide a conceptual framework for the identification of fungi, encouraging the approach of integrative (polyphasic) taxonomy for species delimitation, i.e. the combination of genealogy (phylogeny), phenotype (including autecology), and reproductive biology (when feasible). This allows objective evaluation of diagnostic characters, either phenotypic or molecular or both. Verification of identifications is crucial but often neglected. Because of clade-specific evolutionary histories, there is currently no single tool for the identification of fungi, although DNA barcoding using the internal transcribed spacer (ITS) remains a first diagnosis, particularly in metabarcoding studies. Secondary DNA barcodes are increasingly implemented for groups where ITS does not provide sufficient precision. Issues of pairwise sequence similarity-based identifications and OTU clustering are discussed, and multiple sequence alignment-based phylogenetic approaches with subsequent verification are recommended as more accurate alternatives. In metabarcoding approaches, the trade-off between speed and accuracy and precision of molecular identifications must be carefully considered. Intragenomic variation of the ITS and other barcoding markers should be properly documented, as phylotype diversity is not necessarily a proxy of species richness. Important strategies to improve molecular identification of fungi are: (1) broadly document intraspecific and intragenomic variation of barcoding markers; (2) substantially expand sequence repositories, focusing on undersampled clades and missing taxa; (3) improve curation of sequence labels in primary repositories and substantially increase the number of sequences based on verified material; (4) link sequence data to digital information of voucher specimens including imagery. In parallel, technological improvements to genome sequencing offer promising alternatives to DNA barcoding in the future. Despite the prevalence of DNA-based fungal taxonomy, phenotype-based approaches remain an important strategy to catalog the global diversity of fungi and establish initial species hypotheses.