AbstractThe phylogeny of the genus Diploschistes was investigated using nucleotide sequences of the nuclear ITS rDNA region (ITS1, ITS2 and 5.8S rDNA). Sequences of 22 Diploschistes species were aligned to those of six other species of Thelotremataceae, Graphis scripta and Aspicilia cinerea, with the last used as an outgroup. The alignment was analysed cladistically using maximum parsimony. In the most parsimonious trees, Diploschistes is monophyletic, with D. ocellatus being a sister group to the remaining Diploschistes spp. (= Diploschistes s. str.). A previous cladistic analysis of morphological data suggested an evolutionary trend within the genus from perithecioid to urceolate ascomata. The present ITS data suggest the opposite: perithecioid ascomata are apparently an apomorphic character within the genus, with the actinostomus group forming a derived monophyletic clade. However, the topology within Diploschistes s. str. Lacks strong bootstrap support.