Abstract:
Chaetomium globosum, the type species of the genus, is ubiquitous, occurring on a wide variety of substrates,
in air and in marine environments. This species is recognised as a cellulolytic and/or endophytic fungus. It
is also known as a source of secondary metabolites with various biological activities, having great potential in the
agricultural, medicinal and industrial fields. On the negative side, C. globosum has been reported as an air contaminant
causing adverse health effects and as causal agent of human fungal infections. However, the taxonomic
status of C. globosum is still poorly understood. The contemporary species concept for this fungus includes a
broadly defined morphological diversity as well as a large number of synonymies with limited phylogenetic evidence.
The aim of this study is, therefore, to resolve the phylogenetic limits of C. globosum s.str. and related species.
Screening of isolates in the collections of the CBS-KNAW Fungal Biodiversity Centre (The Netherlands) and the
China General Microbiological Culture Collection Centre (China) resulted in recognising 80 representative isolates
of the C. globosum species complex. Thirty-six species are identified based on phylogenetic inference of six loci,
supported by typical morphological characters, mainly ascospore shape. Of these, 12 species are newly described
here. Additionally, C. cruentum, C. mollipilium, C. rectum, C. subterraneum and two varieties of C. globosum are
synonymised under C. globosum s.str., and six species are resurrected, i.e. C. angustispirale, C. coarctatum, C. cochliodes,
C. olivaceum, C. spiculipilium and C. subglobosum. Chaetomium ascotrichoides is segregated from C. madrasense
and the genus name Chaetomidium is rejected. Five species, including C. globosum s.str., are typified here to
stabilise their taxonomic status. A further evaluation of the six loci used in this study as potential barcodes indicated
that the 28S large subunit (LSU) nrDNA and the internal transcribed spacer regions and intervening 5.8S nrRNA (ITS)
gene regions were unreliable to resolve species, whereas β-tubulin (tub2) and RNA polymerase II second largest
subunit (rpb2) showed the greatest promise as DNA barcodes for differentiating Chaetomium species. This study
provides a starting point to establish a more robust classification system for Chaetomium and for the Chaetomiaceae.
