The Caloplaca holocarpa group in the Nordic countries, except Iceland, is defined genetically using the nrlTS DNA gene. The members are analysed with regard to morphology, anatomy, ecology, and chemistry. The results show that C. holocarpa seems to be a very small group, but there are many morphologically similar species outside the group. Within the group several species have been confused, but it is shown that C. holocarpa, C. pyracea, and C. vitellinula are separate taxa. Caloplaca cerinella also belongs to the group whereas C. cerinelloides does not, but is included in the treatment because of its similarity to the former species. Caloplaca lithophila H. Magn. is a synonym of either C. holocarpa or C. vitellinula, most probably of the latter. Many specimens determined to C. holocarpa belong to Caloplaca oasis, but this species is shown to have much more variable morphology and wider ecology and distribution than previously understood. Caloplaca oasis has also been confused with C. polycarpa, which is similar, but morphologically and genetically distinct, even though related. Neither of the two species belong to the C. holocarpa group, but are related to the C. citrina group, not to the C. velana group as usually believed. Other species from northern and central Europe similar to C. holocarpa belong in other groups. The treated species are described and illustrated in colour. Distribution maps are given for the study area. A key to species in northern Europe similar to C. holocarpa is also provided.

Two species of Placopyrenium, P. cinereoatratum and P. formosum, occur on siliceous rocks at the margins of rivers and lakes. Placopyrenium cinereoatratum is sometimes parasitic on Staurothele fissa; P. formosum is described as a new species, and is initially parasitic on Aspicilia aquatica.

The silicicolous lichen species, Rinodina etayoi Giralt & van den Boom, is described as new from inland localities of Fuerteventura and Lanzarote (Canary Islands). It is characterized by a crustose, whitish thallus containing atranorin, zeorin, chloroatranorin and stictic acid, hemispheric pseudolecanorine apothecia containing, a proper exciple inspersed with numerous and large oil drops, and by ascospores of the Mischoblastia-type. The joint occurrence of pannarin, stictic acid and Mischoblastia-type ascospores makes R. etayoi unique within the genus.

Lecanactis rubra is described as new to science. It is characterized by having rounded to irregular or lirellate ascomata, relatively wide 3-septate ascospores and by the production of gyrophoric acid and an anthraquinone. The species is known only from the type locality in the deciduous dry forests in the western part of Madagascar.

The genus Mycoblastus in cool temperate latitudes of the Southern Hemisphere is reviewed. Eight species are treated in detail: M. bryophilus Imshaug ex Kantvilas sp. nov., from Campbell Island and Tasmania; M. campbellianus (Nyl.) Zahlbr., M. coniophorus (Elix & A.W. Archer) Kantvilas & Elix comb. nov. and M. dissimulans (Nyl.) Zahlbr., all widespread across the austral region; M. disporus (C. Knight) Kantvilas comb. nov., from New Zealand and Tasmania; M. kalioruber Kantvilas sp. nov, from Tasmania; M. sanguinarioides Kantvilas sp. nov., from Tasmania and south-eastern Australia; and M. leprarioides Kantvilas & Elix sp. nov., from south-eastern Australia (Victoria). Notes are provided on many other species of Mycoblastus, including those recognised for the Northern Hemisphere, and those originally described from austral regions but now excluded from the genus. Major characters of the genus are discussed, including thallus morphology and chemistry, apothecial pigments and ascus structure. It is suggested that the genus is heterogeneous and that some of its closest affinities may lie with the family Megalariaceae and the genus Japewia.

Rinodina brasiliensis, a corticolous isidiate species with large Pachysporaria-type ascospores is described from south-eastern Brazil. The new species is closely related to R. dolichospora and to R. guianensis.Rinodina confinis is a synonym of R. dolichospora. Notes on the taxonomy, morphology, anatomy, chemistry and distribution of these three taxa are given. Descriptions and iconography are provided. A key to species is also included.

Two surveys of the lichen and bryophyte flora growing on oak twigs from a Welsh and a Danish locality were compared with additional data on bark pH and % nitrogen in thalli of Hypogymnia physodes. Despite differences in climate and lichen flora, both sites showed a shift in the lichen communities from nitrogen sensitive (nitrophobe) to nitrogen tolerant (nitrophile) species, which was correlated with both increasing bark pH and an increase in total nitrogen in thalli of H. physodes. The floristic survey from Wales was a repetition of a study eight years earlier (Wolseley & Pryor 1999) now showing a loss of nitrophobes in all sites and the appearance of nitrophiles in pasture sites in 2003. This study demonstrates that lichens on twigs can be used as an early warning system to detect a response to changes in land management and nitrogen deposition.