Polyphasic characterisation of Chaetomium species from soil and compost revealed high number of undescribed species

- A phylogenetic tree of Chaetomium was provided for all available type-derived sequences.
- Seven new Chaetomium species were recognized from China.
- Growth temperature and species groups were studied.
- Two closely related species were delimited.

This study investigated 46 Chaetomium strains isolated from soil and compost from China. In total 14 species were recognised, of which seven were described as new species (i.e. Chaetomium angulare, Chaetomium cirrhata, Chaetomium heterothallicum, Chaetomium laterale, Chaetomium longiciliata, Chaetomium microthecia, Chaetomium uniseriatum). Growth temperature profiles of these fungi revealed that 11 species are mesophilic; C. angulare and Chaetomium jodhpurense are thermotolerant; Chaetomium thermophilum var. dissitum is thermophilic, with temperature maxima above 50 °C. Among the 46 strains, 39 were shown to be homothallic. Mating experiments were conducted for the remaining seven strains that are morphologically and phylogenetically closely related. The results of the mating experiment, together with the four-locus (ITS, LSU, RPB2, TUB) phylogeny and a pairwise homoplasy index (PHI) test, supported the division of these seven additional strains into two heterothallic species that are herein described as C. heterothallicum and C. uniseriatum. A three-locus (ITS, LSU, TUB) phylogenetic tree based on all currently accepted species that have available type-derived sequences revealed that Chaetomium species clearly grouped in six phylogenetic groups which showed a certain correspondence with their morphology and temperature profiles.