Notes on lichenicolous taxa of the asexual fungal genera Intralichen and Trimmatostroma, with a revised key and descriptions of four new species

Abstract: Diederich, P. 2021. Notes on lichenicolous taxa of the asexual fungal genera Intralichen and Trimmatostroma, with a revised key and descriptions of four new species. – Herzogia 34: 101–126. The genus Intralichen comprises several mainly intrahymenial lichenicolous species of unknown phylogenetic affinities, each reported from a very large host-spectrum, with many reports obviously representing wrong identifications. We suggest restricting the use of each of these species names to collections growing on the same host genus as the type specimen, i.e., all other reports from different hosts are considered uncertain. Intralichen christiansenii is considered as a synonym of I. lichenicola, a species confined to Candelariella species. Intralichen lichenum s. str. is a poorly known and rarely collected species from Arthoniales hosts, while similar populations on Strangospora are treated as I. aff. lichenum. Intralichen baccisporus has not been revised, as sufficient material from the many Teloschistaceae genera was not available. Morphologically similar species growing on the thalli, not in the hymenium, of various lichen hosts are included in the genus Trimmatostroma, although most lichenicolous species do not seem to be related to the generic type. The new species Trimmatostroma acetabuli (on Pleurosticta acetabulum), T. denigrans (on Lecanora horiza), T. rouxii (on Opegrapha durieui and other saxicolous Arthoniales) and T. vandenboomii (on Myriolecis albescens) are described. Fertile material of T. arctoparmeliae has been studied, with the result that this species is combined as Sphaerellothecium arctoparmeliae. A revised key to all known lichenicolous species of Intralichen and Trimmatostroma is given.