To test the phylogenetic position of phenotypically peculiar species in the Physciaceae we generated 47 new sequences (26 of nrITS region and 21 of mtSSU rDNA) from 19 crustose taxa of Physciaceae mainly from the genus Rinodina. Phylogenetic analysis confirmed the Buellia and Physcia groups. The analysis revealed a considerable variability of characters traditionally used for classification, especially in the delimitation of the genera Buellia and Rinodina. While ascus types agree well with the distinction of the Buellia and Physcia groups, none of the other traditional characters, including excipulum type and ascospore thickening, were consistent within subclades of the Physcia group. We suggest that both excipulum type and ascospore characters are rather dynamic in the evolution of Rinodina species and only appear consistent in morphologically more complex foliose and fruticose groups, which are characterized by thallus characters not present in the crustose groups. Two recent taxonomic changes are supported by molecular characters: Endohyalina insularis (syn. ‘Rinodina’ insularis) and Rinodina lindingeri (syn. ‘Buellia’ lindingeri). In addition Rinodina parvula (syn. ‘Buellia’ parvula) is reinstated. New records for Endohyalina brandii, E. diederichii, E. insularis and Rinodina albana are presented.

Five taxa of the genera Omphalodina and Rhizoplaca known from continental Antarctica are reassessed in order to identify a remarkable species collected from northern Victoria Land, for which the new combination Rhizoplaca macleanii (C.W. Dodge) Castello is proposed here. This poorly known species is known only from continental Antarctica. Two synonyms are discussed: Omphalodina exsulans (Th. Fr.) C. W. Dodge and O. siplei (C. W. Dodge & G. E. Baker) C. W. Dodge are synonyms of Rhizoplaca melanophthalma (DC.) Leuckert & Poelt. The correct name of another species is Tephromela priestleyi (C. W. Dodge) Øvstedal. The name O. johnstonii (C. W. Dodge) C. W. Dodge should be abandoned, type material being too scanty for a reliable identification. A contribution to the flora of the Terra Nova Bay area (northern Victoria Land) is provided, with two additional species, including Buellia vilis Th. Fr. new to Antarctic regions, and two nomenclatural corrections.

Tetramelas phaeophysciae, a new obligately lichenicolous species occurring in Scandinavia, Iceland and Greenland, is described, and the closely related Buellia pulverulenta, together with B. triphragmioides, are transferred to Tetramelas. Phylogenetic reconstructions based on sequence data from nITS1-5.8S-ITS2 rDNA, using Bayesian inference and parsimony analyses, support the segregation of the new species from B. pulverulenta as well as the segregation of Tetramelas and Diplotomma from Buellia s. str.

Two new corticolous species, Hafellia alisioae and H. gomerana (lichenized Ascomycetes, Physciaceae), collected from twigs of coastal shrubs on the Canary Islands are described. The new species are discussed in relation to other Hafellia species with similar characters. An overview and a key for 23 corticolous species of Hafellia with 2-celled ascospores is provided.

ITS rDNA sequence data shows that Diploicia and Diplotomma species form a monophyletic clade distinct from other Buellia species. This indicates that Diplotomma merits acceptance as a genus, and suggests that Diploicia should be treated as a synonym of Diplotomma, the earlier name. The data also shows Diploicia subcanescens, considered the fertile counterpart in a species pair with D. canescens, is nested within D. canescens and should be treated as a synonym despite reported chemical differences. In addition, the molecular data support the distinctness of Diplotomma rivas-martinezii, a species restricted to gypsum rocks in Spain, from the widespread D. venustum, which grows on calcareous rocks. Aposymbiotic cultures suggest that D. rivas-martinezii also differs from D. venustum in its germination and isolation success rates. One new combination is made: Diplotomnta pulverulenta (Anzi) D. Hawksw. (syn. Abrothallus pulverulentus Anzi) for the lichenicolous species previously known as Buellia pulverulenta.

A new corticolous species of Buellia is described from La Palma and La Gomera (Canary Islands). It is mainly characterized by its strongly ornamented, (l-2)-3-septate ascospores with apical and septa thickenings, which follow an ascospore-ontogeny of type B, and its chemistry. The new species is compared with the related Buellia lauricassiae (Fée) Mü. Arg. and B. lauricassiaeoides Aptroot. Illustrations of the ascospores of B. laurocanariensis and B. lauricassiaeoides are presented. A habit photograph of the new species is also provided.