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.

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 new corticolous species belonging to the lichen family Pertusariaceae, Pertusaria grassiae Messuti & A.W. Archer, is described from Tucumán Province, Argentina. It is characterized by disciform apothecia covered by a white to greyish white pruina, single-spored asci, ellipsoid and double-walled ascospores and the presence of atranorin.

Hysterium graphideum Speg. is proposed as a synonym of Gloniella graphidoidea Rehm. During the study of the types of both names, the presence of algae associated with the fungal hyphae was found. The main morphological and anatomical characters, and the ecology of the species are 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.

An investigation of the genus Usnea, in the biodiversity hotspot of the Republic of São Tomé and Príncipe in tropical West Africa, is presented here. Fifteen species, or species aggregates, were recorded for the islands: Usnea articulata aggr., Usnea baileyi (Stirt.) Zahlbr., Usnea beckeri P. Clerc & Nadel, Usnea bicolorata Motyka, Usnea erinacea aggr., Usnea exasperata (Müll. Arg.) Motyka, Usnea firmula (Stirt.) Motyka, Usnea krogiana P. Clerc, Usnea longiciliata P. Clerc & Nadel, Usnea nodulosa Swinscow & Krog, Usnea pectinata aggr., Usnea sorediosula Motyka, Usnea submollis J. Steiner, and two undetermined species. Two species of lichen are described as new to science: U. beckeri and U. longiciliata. Both species are characterized by a dense and brittle, dark green thallus, the presence of apothecia surrounded by long cilia-like fibrils, a lack of soredia, and the presence of two unknown substances; however, whereas U. beckeri has a pendant growth form and can reach 25 cm in length, U. longiciliata is differentiated by a shrubby growth form of less than 6 cm. These two species also have different ascospore dimensions. A molecular phylogenetic analysis is presented that lends support to their description as new species. Additionally, Usnea krogiana is noted as new to continental Africa and nine Usnea species or aggregates are noted as new to the Islands of São Tomé and Príncipe in the Gulf of Guinea.

Normandina acroglypta, as recently circumbscribed, is shown to comprise two species: N. acroglypta s. str. with subsquamulose marginal areoles, two unidentified terpenoids by thin-layer chromatography, and growing over rock; and N. chlorococca, with convex marginal areoles, zeorin or no substances detected by thin-layer chromatography, and growing over bark. Normandina dictyospora is newly described from the Falkland Islands and is characterized by relatively large, submuriform ascospores, and no substances detected.

While the diversity of foliicolous lichen-forming fungi has been explored in substantial depth, relatively little attention has been paid to their algal symbionts. We studied the unicellular green phycobionts of the lecanoralean lichens Bacidina (Ramalinaceae), Byssoloma, Fellhanera and Tapellaria (Pilocarpaceae) and graphidalean Gyalectidium (Gomphillaceae) from two extratropical foliicolous communities in continental Spain and the Canary Islands. We examined the pyrenoids of algal symbionts within thalli using TEM, and obtained several algal nrSSU and rbcL sequences from whole thalli, and also from cultures isolated from some of these lichens. Pyrenoid structure and molecular sequence data provided support for recognizing Chloroidium (Watanabeales, Trebouxiophyceae) as phycobiont in thalli of Byssoloma subdiscordans and Fellhanera bouteillei (Pilocarpaceae) in both communities. Bacidina apiahica (Ramalinaceae) and Tapellaria epiphylla (Pilocarpaceae) likewise appeared to partner with Chloroidium based on the presence of the same pyrenoid type, although we were able to obtain a phycobiont sequence only from a culture isolate of the latter. These results contrast with those obtained previously from a foliicolous lichen community in southern Florida, which revealed only strains of Heveochlorella (Jaagichlorella) as phycobiont of foliicolous Pilocarpaceae and Gomphillaceae. On the other hand, the pyrenoid we observed in the phycobionts associated with Gyalectidium setiferum and G. minus corresponded to that of Heveochlorella (Jaagichlorella). However, the poor quality of the phycobiont sequence data obtained from G. minus, probably due to the presence of epibiontic algae, could not provide additional perspective on the pyrenoid structure observations. Nonetheless, clear differences in pyrenoid ultrastructure can allow Chloroidium and Heveochlorella phycobionts to be distinguished from each other in TEM. Our results indicate a greater diversity of unicellular green-algal symbionts in foliicolous communities from Spain than previously observed in other geographical areas, and suggest that further studies focused on symbiont pairing in these communities might reveal distinctive and varied patterns of phycobiont preference.

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.