Consolidation ofChloridium: new classification into eight sections with 37 species and reinstatement of the generaGongromerizaandPsilobotrys

Chloridiumis a little-studied group of soil- and wood-inhabiting dematiaceous hyphomycetes that share a rare mode of phialidic conidiogenesis on multiple loci. The genus has historically been divided into three morphological sections,i.e.Chloridium,Gongromeriza, andPsilobotrys. Sexual morphs have been placed in the widely perceived genusChaetosphaeria, but unlike their asexual counterparts, they show little or no morphological variation. Recent molecular studies have expanded the generic concept to include species defined by a new set of morphological characters, such as the collar- like hyphae, setae, discrete phialides, and penicillately branched conidiophores. The study is based on the consilience of molecular species delimitation methods, phylogenetic analyses, ancestral state reconstruction, morphological hypotheses, and global biogeographic analyses. The multilocus phylogeny demonstrated that the classic concept ofChloridiumis polyphyletic, and the original sections are not congeneric. Therefore, we abolish the existing classification and propose to restore the generic status ofGongromerizaandPsilobotrys. We present a new generic concept and defineChloridiumas a monophyletic, polythetic genus comprising 37 species distributed in eight sections. In addition, of the taxa earlier referred toGongromeriza, two have been redisposed to the new genusGongromerizella. Analysis of published metabarcoding data showed thatChloridiumis a common soil fungus representing a significant (0.3 %) proportion of sequence reads in environmental samples deposited in the GlobalFungi database. The analysis also showed that they are typically associated with forest habitats, and their distribution is strongly influenced by climate, which is confirmed by our data on their ability to grow at different temperatures. We demonstrated thatChloridiumforms species-specific ranges of distribution, which is rarely documented for microscopic soil fungi. Our study shows the feasibility of using the GlobalFungi database to study the biogeography and ecology of fungi.