List of Arthonia species

This is a list of species in the fungal genus Arthonia, which contains both lichen-forming fungi, and lichenicolous (lichen-dwelling) fungi. As of September 2025^[update], Species Fungorum (in the Catalogue of Life) accepts 164 species of Arthonia.^[1] The Arthonia species accepted by Species Fungorum are those for which they have expressed a taxonomic opinion, and does not necessarily represent the total number of species in the family. Although more than 1600 taxa have at one time been placed in the genus, the majority of these are now either considered synonyms of other species, have been moved to other genera, or are too little-known and have been collected too infrequently to have had a taxonomic opinion expressed about them.^[2] Recent estimates for the number of species in the genus include 491 (2008),^[3] 500 (2017),^{[4][note 1]} and 50 species with 300 "orphaned"^{[note 2]} species (2021).^[5] According to a 2018 review of lichenicolous fungi, there are 139 lichenicolous fungi and 1 lichenicolous lichen in Arthonia (Arthonia infectans is the single known example of the latter). In the following list, the host(s) of the lichenicolous taxa are given.^[6]