Taxonomy, phylogeny and identification of Chaetomiaceae with emphasis on thermophilic species

Chaetomiaceae comprises phenotypically diverse species, which impact biotechnology, the indoor environment and human health. Recent studies showed that most of the traditionally defined genera in Chaetomiaceae are highly polyphyletic. Many of these morphology-based genera, such as Chaetomium , Thielavia and Humicola , have been redefined using multigene phylogenetic analysis combined with morphology; however, a comprehensive taxonomic overview of the family is lacking. In addition, the phylogenetic relationship of thermophilic Chaetomiaceae species with non-thermophilic taxa in the family is largely unclear due to limited taxon sampling in previous studies. In this study, we provide an up-to-date overview on the taxonomy and phylogeny of genera and species belonging to Chaetomiaceae , including an extensive taxon sampling of thermophiles. A multigene phylogenetic analysis based on the ITS (internal transcribed spacers 1 and 2 including the 5.8S nrDNA), LSU (D1/D2 domains of the 28S nrDNA), rpb2 (partial RNA polymerase II second largest subunit gene) and tub2 (β-tubulin gene) sequences was performed on 345 strains representing Chaetomiaceae and 58 strains of other families in Sordariales . Divergence times based on the multi-gene phylogeny were estimated as aid to determine the genera in the family. Genera were delimited following the criteria that a genus must be a statistically well-supported monophyletic clade in both the multigene phylogeny and molecular dating analysis, fall within a divergence time of over 27 million years ago, and be supported by ecological preference or phenotypic traits. Based on the results of the phylogeny and molecular dating analyses, combined with morphological characters and temperature-growth characteristics, 50 genera and 275 species are accepted in Chaetomiaceae . Among them, six new genera, six new species, 45 new combinations and three new names are proposed. The results demonstrate that the thermophilic species fall into seven genera ( Melanocarpus , Mycothermus , Remersonia , Thermocarpiscus gen. nov. , Thermochaetoides gen. nov. , Thermothelomyces and Thermothielavioides ). These genera cluster in six separate lineages, suggesting that thermophiles independently evolved at least six times within the family. A list of accepted genera and species in Chaetomiaceae , together with information on their MycoBank numbers, living ex-type strains and GenBank accession numbers to ITS, LSU, rpb2 and tub2 sequences is provided. F