Abstract
Trichomerium is a genus of foliar epiphytes with the appearance of sooty moulds, mostly occurring on the surface of living leaves and apparently gaining their nutrients from insect exudates. Species have ascostromata with setae and develop on a loosely interwoven mycelial mass of dark brown hyphae, while asci have a bitunicate appearance with hyaline ascospores. In this study, we made 16 collections of Trichomerium from Thailand. All were isolated, and the LSU and ITS rDNA gene regions sequenced. Phylogenetic analysis indicated that the Trichomerium species form a monophyletic clade within Chaetothyriales and warrant the introduction of a new family Trichomeriaceae. Bootstrap support for the Chaetothyriales is 100 % and clearly separates Trichomeriaceae from Capnodiales which are morphologically very similar. A detailed account of Trichomerium is provided and we describe and illustrate three new species based on morphological and molecular data. We propose that T. foliicola is adopted as the generic type of Trichomerium because it has been impossible to obtain the holotype specimen of T. coffeicola and also no molecular data exists in worldwide databases for this species or genus.