Soil ascomycetes from Spain. XIV. The Chaetomiaceae of La Palma (Canary Islands)

The Canary Islands, located in the Atlantic Ocean within the Macaronesian biogeographic region, consist of seven main islands alongside numerous smaller ones of volcanic origin, representing the southernmost region of Spain. This archipelago shows a variety of microclimates and ecological settings, encompassing from laurisilva cloud forests to montane pine forests and deserts, responsible for diverse flora and fauna rich in endemism. Despite considerable research focused on the biodiversity of plant and animal life, knowledge regarding fungi, particularly micromycetes, remains comparatively limited. Building on our ongoing investigation of soil-borne ascomycetes of the Canary Islands, initiated several decades ago, we collected samples from the southern region of La Palma Island. At the laboratory, these samples were processed using different semi-selective techniques aimed at isolating ascomycetes, such as the Warcup’s soil plate method, the activation of soil dormant ascospores with 5 % acetic acid, and ToKaVa hair baiting method. After a phenotypic characterization, subsequent molecular identification of the fungal strains was conducted through amplification and sequencing of the Internal Transcribed Spacer (ITS) and the domains D1-D2 of the Large Subunit (LSU) regions of nuclear ribosomal DNA, and fragments of the RNA polymerase II second largest subunit ( rpb 2), β-tubulin ( tub 2) and translation elongation factor 1-alpha ( tef ) genes. Preliminary taxonomic assignment was carried out using BLAST searches, followed by phylogenetic studies for precise taxonomic delimitation. Among the identified members of the Chaetomiaceae , noteworthy taxa include Achaetomium aegilopsis , Canariomyces arenarius , Carteria arctostaphyli , Ovatospora senegalensis , Parathielavia kuwaitensis , Pseudohumicola alba, and P. glauca , representing the first documented occurrences in volcanic soils. Furthermore, the discovery encompasses the description of three new genera ( Oidiosporium , Phaeohyphomyces and Steirochaetomium ) and nine new species ( Botryotrichum pseudomurorum , Canariomyces asexualis , Carteria canariensis , Oidiosporium botulisporum , Phaeohyphomyces canariensis , Pseudohumicola cinnamobrunnea , P. intercalispora , P. variispopra and Steirochaetomium canariensis ) within this fungal family. These findings underscore the significance of volcanic soils of La Palma Island as reservoirs of novel micromycetes, particularly emphasizing the prevalence of Chaetomiaceae members as revealed by the applied isolation methodologies.