Mendogiadiffusa sp. nov. and an updated key to the species of Mendogia (Myriangiaceae, Dothideomycetes)

Background Mendogia belongs to Dothideomycetes and its members are epiphytic on living bamboo culms or palms and distributed in tropical regions. Currently, the genus comprises seven species. Another collection resembling Mendogia was collected from the leaves of Fagales sp. in Thailand. Morphological characteristics and multilocus phylogenetic analyses, using ITS, LSU and SSU sequences, showed that the fungus is new to science, described herein as Mendogiadiffusa. Mendogiadiffusa is characterised by apothecial ascostromata, a carbonised epithecium, dark brown setae on the ascostromatal surface, hyaline paraphysoids, ovoid to clavate asci and oblong to elliptical, muriform ascospores. The fungus has a dark pigmented surface and is occasionally facultatively associated with patches of green algae, but not actually lichenised. Instead, the fungus penetrates the upper leaf surface, forming dark pigmented isodiametric cells below the epidermis. New information Re-examination of specimens of M.chiangraiensis, M.macrostroma and M.yunnanensis revealed the absence of algal associations. The status of Mendogiaphilippinensis (= M.calami) and M.bambusina (= Uleopeltisbambusina) was established, based on morphological comparisons and previous studies. Comprehensive morphological descriptions with phylogenetic analyses support M.diffusa as a novel species in Myriangiaceae. An updated key to the known species of the genus is also provided.