Arthonia hawksworthii sp nov (Ascomycota, Arthoniaceae) on Dimelaena oreina from Turkey

Arthonia hawksworthii is described on the thallus of Dimelaena oreina from two localities in Turkey. It is most similar to A. gelidae, a lichenicolous species confined to Placopsis gelida, but mainly differs from this species in that it has ascospores with a gelatinous sheath that stain red in 1-Lugol and an epithecium that is light to dark brown with an olivaceous tinge in KOH. The new species is the first Arthonia species reported on Dimelaena.