A new lichenized fungus, Lecanora microloba Śliwa & Flakus, is described from the subnival belt of the Polish Tatra Mountains. It is characterized by small, saxicolous thalli with minutely lobulate marginal areoles and mostly broadly sessile and constantly pale coloured apothecia that are grouped predominantly in the centre of the thallus. Anatomically the species is distinguished by coarse granules in the epithecium which are distinctly bright in polarized light. The species contains gyrophoric and usnic acids, zeorin and an unknown terpene as secondary metabolites.

The new genus Silobia M. Westb. & Wedin is proposed for the Acarospora smaragdula group, which is taxonomically and nomenclaturally revised in Sweden. The proposed taxonomy results from our former molecular phylogeny, together with morphological and anatomical investigations and analysis of secondary metabolites. Seven species are recognized in Sweden in this paper: Silobia dilatata sp. nov., S. myochroa sp. nov., S. rhagadiza comb. nov., S. rufescens comb. nov., S. scabrida comb. nov., S. smaragdula comb. nov. and S. tangerina sp. nov. Acarospora alberti, A. amphibola, A. isortoquensis, A. murina and A. undata are recognized as synonyms of S. smaragdula, Acarospora verruciformis as a synonym of S. scabrida and A. scyphulifera as a synonym of S. rhagadiza. The following names are lectotypified: Acarospora amphibola, A. amphibola f. testacea, A. lesdainii, A. lesdainii var. subochracea, A. murina, A. scyphulifera f. subdiscreta, Endocarpon smaragdulum, Lecanora rhagadiza and Sagedia rufescens. Acarospora scyphulifera is neotypified. Acarospora fusca is excluded from the Swedish checklist as the specimen was found to belong to S. rufescens. A key to the species is presented.

Aspicilia fluviatilis and A. granulosa, two arctic and/or (sub)alpine species with elongate ± diverging and ± branching marginal areoles, are described as new and compared with similar species occurring in Fennoscandia. A parsimony analysis based on ITS indicates a close relationship with the mainly coastal A. epiglypta. Aspicilia epiglypta, A. disserpens and A. sublapponica are lectotypified and A. disserpens is reduced to synonymy with A. perradiata. Aspicilia alboradiata and A. circularis are excluded from the Fennoscandian lichen biota. A key to Fennoscandian Aspicilia species with radiating thalli and/or elongate ± diverging and ± branching marginal areoles is also presented.

A new lichen species, Aspicilia digitata Sohrabi & Litterski, is described and illustrated. It differs from the Eurasian and American A. fruticulosa and A. hispida by having a more or less spherical thallus, a very intricate structure of finger-like, cylindrical branchlets and black spots on the tips of the branchlets. Aspicilia digitata is a terricolous vagrant species found at high altitudes in the Tian-Shan Mountains, Kyrgyzstan. It is not known in the fertile condition and presumably reproduces by fragmentation. Molecular comparisons with other related species are provided.

The new species Lecanora ulrikii from Bhutan and Thailand is described. It belongs to Lecanora s. str. and is characterized by relatively large, orange-brown to brown apothecia that are constricted at the base, a clear to inspersed hymenium, an epihymenium of the glabrata-type, and by the presence of atranorin, usnic acid and the isoarthothelin chemosyndrome. Further, three species, L. arthothelinella, L. austrotropica and L. subimmergens, are reported for the first time from Thailand.

The new lichenicolous fungus, Abrothallus halei sp. nov., is described. The species is characterized by having 4-celled ascospores with a strongly constricted median septum, which split into two 2-celled part-spores, even when still inside the ascus. This is the first Abrothallus known from the genus Lobaria, and the species is reported from Norway and the USA, occurring on L. quercizans and L. pulmonaria.

Two new corticolous lichen species are described, Lepraria nothofagi Elix & Kukwa (atranorin, strepsilin, porphyrilic acid) from Argentina and L. stephaniana Elix, Flakus & Kukwa (4-O-methylleprolomin, zeorin, salazinic acid, unknown terpenoid) from pre-Andean Amazon forest of Bolivia. In addition, the paper presents new records of 16 species of Lepraria from South America. Lepraria adhaerens, and L. diffusa are new to the Southern Hemisphere; L. borealis is new to South America; L. alpina is new to Chile, Colombia, Peru and Venezuela; L. caesioalba (chemotype I) is new to Venezuela, L. lobificans new to Argentina, L. pallida new to Peru, and L. sipmaniana new to Bolivia and Chile. The Chilean records of L. membranacea appeared to belong to L. sipmaniana. Therefore, the number of Lepraria spp. known at present from South America is enlarged to 27 species. 4-O-methylleprolomin is reported for the second time from lichens.

The recently described genus Vahliella (Peltigerales, Ascomycetes) has repeatedly appeared outside the Pannariaceae in molecular phylogenies. Here we include data from additional species of the genus and utilize mtSSU rDNA and RPB1 sequences to confirm its placement as the sister to a group consisting of Lobariaceae, Massalongiaceae, Nephromataceae and Peltigeraceae, in the Peltigerales. The new family Vahliellaceae Wedin, P. M. Jørg. & S. Ekman is described for the genus, and its morphological characteristics are briefly discussed.

Population genetic studies of lichen-forming fungi and their algae require appropriate sampling schemes that ensure representative sampling of the genetic variability. One question is whether mycobiont and photobiont populations require different sampling strategies. Here, I applied rarefaction methods to a dataset containing three microsatellite loci of Lobaria pulmonaria and three microsatellite loci of its green-algal photobiont, Dictyochloropsis reticulata. I analysed the sample sizes required for 1) the number of individuals per population, 2) the number of individuals required across a landscape and 3) the number of populations. The analyses were performed separately for the mycobiont and photobiont loci to detect any differences in the accumulation of genetic diversity among the symbionts that would require different sampling schemes. About 20 individuals were sufficient at the population level; within landscapes, 300–400 samples and about 25–30 populations covered most of the allelic diversity. The results indicated that a slightly higher sampling effort was required for the photobiont than for the mycobiont. The optimal sampling strategy strongly depends on the research question, the spatial scale of investigation, and the type of analysis to be performed with the data.