The lowland area of southern Vietnam contains a high diversity of corticolous, crustose lichens, particularly in the family Graphidaceae. Two species, Acanthothecis verrucosa S. Joshi, Upreti & Hur and Graphis exuta S. Joshi, Upreti & Hur, are described new to science. Acanthothecis verrucosa is characterized by a verrucose, olive green thallus containing irregular to shortly lirellate apothecia, hyaline to brownish proper exciple apically lined by robust periphysoids, muriform ascospores, 30–70 × 15–20 μm, and the presence of psoromic and subpsoromic acids. Graphis exuta is characterized by a smooth, greenish white thallus, simple lirellae lacking thalline margin, entire labia coarsely white pruinose towards slit, muriform ascospores, 20–35×10–13 μm, and norstictic acid in the thallus. A new name, Acanthothecis yokdonensis S. Joshi & Hur, is proposed here for the species Acanthothecis salazinica S. Joshi & Hur, a later homonym of A. salazinica van den Boom & Sipman. In addition, 34 species from Vietnam are newly reported. A world key to the group of Graphis species characterized by short, simple and sessile lirellae lacking or with basal thalline margins (nuda-morph) is presented.

A corticolous species, Anisomeridium flavovulcanus, is described. It has so far been found in the Carribean and Pacific lowland rainforests of Costa Rica, where it is a frequent lichen in the understorey. This conspicuous lichen is characterized by large conical conidiomata, which release a yellow conidial mass at the apex. Dimorphic conidia occur in the same conidiomata: 1-septate microconidia and thick walled globose macroconidia. Ascomata were found only twice; the inconspicuous perithecia are hemispherical, semi-emergent with an apical ostiole, the asci are cylindrical with a cruciform ocular chamber and the ascospores are uniseriately arranged.

The circumscription of the lichenized ascomycete genus Icmadophila Trevis. in the family Icmadophilaceae Triebel was investigated. Sequences of the internal transcribed spacer (ITS) region and large subunit of nuclear ribosomal DNA (nuLSU) were generated for the five Icmadophila species and additional members of Icmadophilaceae from the genera Dibaeis, Endocena, Knightiella, Siphula, Siphulella and Thamnolia. Phylogenetic analyses indicate that three Icmadophila species are closely related: the type, I. ericetorum (L.) Zahlbr., which is widespread in Eurasia and North America, I. aversa (Nyl.) Rambold & Hertel from Central and South America, and I. japonica (Zahlbr.) Rambold & Hertel, which is restricted to Far East Russia and Japan. The genus Knightiella Müll. Arg. is reinstated to accommodate I. splachnirima (Hook.f. & Taylor) D. J. Galloway emend. L. Ludw., which occurs in New Zealand and Australia. Two further species of Knightiella, K. eucalypti (Kantvilas) Kantvilas and K. queenslandica Kantvilas, are found to be unrelated to K. splachnirima, and are accommodated in two newly described genera, Knightiellastrum and Siphulopsis respectively. Knightiellastrum L. Ludw. & Kantvilas is characterized by a squamulose, erhizinate, whitish to pale grey thallus with a green, coccoid photobiont and by containing thamnolic acid. Siphulopsis Kantvilas & A. R. Nilsen is similarly characterized by an erhizinate, whitish to pale grey thallus, with a green, coccoid photobiont and containing thamnolic acid, but is instead fruticose. This study reveals considerable diversity within Australasian Icmadophilaceae; ongoing work in the Southern Hemisphere and tropical regions may reveal additional species in this family and clarify the relationships of these newly described genera.

Caloplaca sol is described as a new species from limestone and basic siliceous rocks on the southern and western coasts of Great Britain. It is characterized by a well-developed, crustose, non-placodioid, epilithic, cracked, orange-yellow thallus, almost concolorous apothecia up to 0·66 mm diameter, and ascospores c. 11·0–12·2–13·0 µm long with a septum c. 0·4×the ascospore length. Caloplaca dalmatica is related but differs in the endolithic or only thinly epilithic thallus. Caloplaca marina is darker orange in colour, with more convex areoles, and is mostly confined to the splash zone of the seashore. Caloplaca maritima differs in the typically more convex, sometimes isolated areoles, and often in the presence of a crenulate thalline margin in young apothecia. Caloplaca itiana is newly reported from Great Britain from coastal limestone; it differs from C. sol in the thallus being endolithic or almost so, and from C. dalmatica in the more completely endolithic thallus and the larger ascospores.

We provide an updated survey for Sri Lanka of species of Graphis sensu Staiger, recently divided into Graphis s. str. and Allographa, including brief descriptions and a key to all 124 species currently known. Six new species are described: Allographa bambusicola Weerakoon, Lücking & Aptroot, a bambusicolous Allographa with entire labia, a laterally carbonized excipulum, 80–100 × 15–17 µm large, muriform ascospores and a rather thick, irregularly verrucose lateral thalline margin of the lirellae; A. weerasooriyana Weerakoon, Arachchige & Lücking, a corticolous Allographa resembling A. rustica Kremp. in overall anatomy and chemistry, but with a verrucose thalline margin of the lirellae and labia not distinctly raised above the thalline margin; Graphis flosculifera Weerakoon, Lücking & Aptroot, a corticolous Graphis resembling G. insulana but differing in the unique disposition of the lirellae and the slightly more elongate ascospores; G. rajapakshana Weerakoon, Lücking & Aptroot, a corticolous Graphis resembling G. desquamescens, including in ascospore size, but with lirellae with a distinct lateral thalline margin; G. rimosothallina Weerakoon, Lücking & Aptroot, a corticolous Graphis with a thick, uneven, rimose thallus and Fissurina-like lirellae, a completely carbonized excipulum and transversely 7-septate ascospores, 32–37 × 8–10 µm; and G. thunsinhalayensis Weerakoon, Arachchige & Lücking, a corticolous Graphis resembling G. subalbostriata but with smaller ascospores and lacking white lines between the striae of the labia. We also validate the name G. verrucoserpens Lücking. A total of 106 species are reported here for the first time from Sri Lanka. A biogeographical comparison with two other well-sampled countries (Costa Rica and Thailand) revealed a significantly higher similarity in species composition with Costa Rica than between Thailand and Costa Rica, suggesting a potential signature of the ‘biotic ferry’ hypothesis, that is the migration of lineages from Gondwana (partly corresponding to the modern Neotropics) via the north-eastwards drifting Indian subcontinent and subsequent interchange with Laurasia (partly corresponding to the modern eastern Paleotropics). However, the evolutionary timeline of the clades involved does not support this hypothesis and suggests an alternative explanation of geologically more recent mid- to long-distance dispersal.