A detailed examination of Malmidea specimens deposited in the herbarium LWG and freshly collected samples resulted in the description of 10 new species. Malmidea glabromarginata has a finely verrucose thallus and granifera-type whitish apothecial margins. Malmidea globosa is characterized by having a strongly verrucose thallus with almost spherical warts and piperis-type apothecial margins. Malmidea incrassatispora has a thalline excipulum and ascospores with end wall thickenings. Malmidea kalbii has a thalline excipulum, dark brown to black apothecial discs and ascospores mostly < 15 μm in length. In Malmidea lutea the medulla of the thallus and verrucae is white to cream-coloured, with beige-coloured apothecial discs. Malmidea palghatensis has a thalline excipulum and with medulla of verrucae pink-coloured. Malmidea rubra has an irregularly verrucose thallus, with the medulla of verrucae orange-red and whitish apothecial margins. Malmidea subindica has light to dark orange-brown apothecial discs, 2–4-spored asci, and broadly ellipsoid ascospores mostly exceeding 30 μm in length. Malmidea upretii has prominent and confluent verrucae with an orange-red medulla, and ascospores exceeding 25 μm in length. Malmidea verrucosa has a characteristic whitish grey, densely verrucose thallus, dark reddish brown apothecial discs and contains atranorin. Additionally, seven species, viz. Malmidea fenicis (Vain.) Kalb et al., M. leptoloma (Müll. Arg.) Kalb & Lücking, M. piae (Kalb) Kalb, M. piperina (Zahlbr.) Aptroot & Breuss, M. reunionis Kalb, M. sulphureosorediata Cáceres et al. and M. vinosa (Eschw.) Kalb et al., are reported as new distributional records for the Indian lichen biota. The world key of Malmidea by Breuss & Lücking (2015) has been updated with all the species discovered after 2015 by mentioning specific couplets.

Canada's endangered Deep-Snow Mountain Caribou (DSC) are endemic to mountainous southern inland British Columbia, where they subsist in winter on an almost exclusive diet of epiphytic hair lichens, especially Bryoria fremontii and B. pseudofuscescens (the high-biomass Bryoria spp.) and Alectoria sarmentosa. Importantly, stand-level hair lichen loadings adequate for the dietary needs of DSC rarely occur in forests younger than c. 120–150 years, an unusual form of old-growth dependence hypothetically linked to certain structural features of old forest ecosystems. Not only does this hypothesis accord well with recent insights into hair lichen ecophysiology, it also allows the formulation of a conceptual ‘hyperabundance’ model for the high-biomass Bryoria spp. and lays the foundation for a similar model for A. sarmentosa. In both cases the models point to a massive standing crop of hair lichens in the overstories of old-growth forests; it is this reservoir that, partly by releasing a constant manna-like rain of thallus fragments into the lower canopy, sustains DSC during the winter half year. The outcome is a sustained-yield system resistant to degradation from overbrowsing, yet vulnerable to fragmentation of old-growth forests by industrial forestry, a process of progressive forage reduction that must ultimately place DSC at risk of winter malnutrition. We conclude that stand-level hair lichen hyperabundance is necessarily an attribute of advanced forest age and, at least in the case of Bryoria, cannot be silviculturally induced in stands younger than c. 120–150 years.

According to International Union for the Conservation of Nature (IUCN) guidelines, all species must be assessed against all criteria during the Red Listing process. For organismal groups that are diverse and understudied, assessors face considerable challenges in assembling evidence due to difficulty in applying definitions of key terms used in the guidelines. Challenges also arise because of uncertainty in population sizes (Criteria A, C, D) and distributions (Criteria A2/3/4c, B). Lichens, which are often small, difficult to identify, or overlooked during biodiversity inventories, are one such group for which specific difficulties arise in applying Red List criteria. Here, we offer approaches and examples that address challenges in completing Red List assessments for lichens in a rapidly changing arena of data availability and analysis strategies. While assessors still contend with far from perfect information about individual species, we propose practical solutions for completing robust assessments given the currently available knowledge of individual lichen life-histories.

Twelve new lichen species are described in the family Arthoniaceae. All are sterile white crusts growing on overhanging trees (and one on living palm fronds) in ten different states in tropical Brazil. In the tropics, sterile crusts so far have been mostly disregarded. They are all characterized by their chemistry and morphology, often including pseudoisidia or soredia, but their phylogenetic relationships have been investigated with sequencing. The following species are described: Arthonia farinosorediata, with shallow soralia and without secondary metabolites; Crypthonia irregularis, with irregular isidia, confluentic acid and sometimes 2ʹ-O-methylperlatolic acid; Crypthonia pseudisidiata, with soft pseudoisidia and without secondary metabolites; Crypthonia stromatica, with sterile stromata and confluentic acid; Cryptophaea constrictopseudisidiata with pseudoisidia, lichexanthone and confluentic acid; Cryptophaea lichexanthopseudisidiata with pseudoisidia and lichexanthone; Cryptophaea lichexanthosorediata with soredia, lichexanthone and divaricatic acid; Cryptothecia lecanorosorediata with soredia and lecanoric acid; Glomerulophoron confluentisorediatum with soredia, confluentic and 2ʹ-O-methylperlatolic acids; Herpothallon psorpseudisidiatum on living palm fronds with a strongly attached thallus, long pseudoisidia and psoromic acid; Myriostigma minisorediatum with soredia and 2ʹ-O-methylperlatolic acid; Pachnolepia longipseudisidiata with long pseudoisidia, and a thallus containing lichexanthone, confluentic acid and 2ʹ-O-methylperlatolic acid.

The new genus Imsharria is proposed for a crustose species found on or near mountain summits on the Falkland Islands. It is separated from other genera of Lecideaceae by a combination of Porpidia-type asci, halonate ascospores, immersed apothecia and a hyaline hypothecium, and forms a distinct branch in the phylogenetic analysis using the markers nrITS and mtSSU. The single species, I. orangei, is characterized by its innate apothecia with a brown disc and a thallus containing norstictic acid and an amyloid (I+ violet) medulla. In addition, Porpidia imshaugii is described for a species from the Falkland Islands resembling P. skottsbergiana but with larger ascospores, and Porpidia navarina is shown to belong in the genus Poeltiaria, with the new combination Poeltiaria navarina being made. A key to the Lecideaceae on the Falkland Islands is provided.

The foliicolous lichen Gallaicolichen pacificus exhibits unique goniocystangia-like structures named peltidiangia and peltidia. Its taxonomic classification within the Ascomycota has been unclear due to the absence of ascomata and lack of molecular data. Here we clarify the phylogenetic affinities of Gallaicolichen pacificus by analyzing mitochondrial small subunit ribosomal RNA (mtSSU) sequences obtained from specimens collected in New Caledonia. Ascomata and ascospores of G. pacificus, previously unknown, are described and illustrated for the first time. The results from the molecular and morphological analyses clearly indicate that Gallaicolichen pacificus belongs to the Porinaceae and is closely related to Porina guianensis. This is a remarkable extension of the already known, wide morphological diversity of thalli and diaspores produced within this family.

During a field trip to the highlands of Mount Meru in Tanzania, two Placopsis specimens were collected. Morphological analyses showed a unique combination of characters not observed in any other published taxa within the genus. The specimens are characterized by their circular soralia, not confluent, crater-shaped, with a prominent white margin and coarse granular pinkish central soredia. Considering the morphological, geographical and genetic data, we propose the designation of a new species, Placopsis craterifera Boluda sp. nov.

Phylloblastia iranica S. Kazemi, Lücking & Sipman sp. nov. is described and illustrated as a new foliicolous lichen. It is characterized by 1-septate, colourless, more or less fusiform, slightly curved ascospores, 9–19 × 4–6 μm. In addition, the foliicolous Strigula buxi Chodat is reported for the first time from Iran, increasing the number of foliicolous lichens known from that country to three, where previously only Gyalectidium caucasicum (Elenk. & Woron.) Vězda was recorded. All three species were found in boxwood (Buxus sempervirens) forest. A key to all known Phylloblastia species worldwide is provided.

The new species Caloplaca tswaluensis is described from Tswalu Kalahari Reserve, Northern Cape Province, South Africa. Caloplaca tswaluensis occurs on the trunks of Vachellia erioloba (camelthorn) trees and is characterized by its 3-septate to quadrilocular ascospores. Molecular data indicate that the new species is placed in the subfamily Teloschistoideae but cannot be assigned to any existing genus and, because its systematic position is unclear, we choose to describe it in Caloplaca s. lat. Caloplaca tswaluensis is compared with other crustose Teloschistaceae species with plurilocular ascospores.

The phylogenetic relationships of the monospecific genus Paratricharia, with the single species P. paradoxa, within the family Gomphillaceae are resolved using newly generated sequences of the mtSSU and nuLSU markers for three specimens collected in Costa Rica. The results support placement as sister to the genus Caleniopsis, the two genera sister to a clade containing the genera Aulaxina and Aulaxinella. This placement confirms earlier studies based on cladistic analysis of phenotype characters and phenotype-based phylogenetic binning, suggesting that apothecial features are more informative for the phylogenetic placement of taxa within Gomphillaceae than thallus characteristics.

A survey of the lichen genus Pseudopyrenula in India is presented, with morphotaxonomic accounts of all six accepted species. Two species, P. himalayana and P. megaspora, are new to science. Both species resemble P. staphyleae but have a lichenized thallus and eccentric ostiole. Furthermore, P. himalayana differs from P. staphyleae in having immersed perithecia and narrower ascospores, while P. megaspora differs in the larger ascospores. Detailed descriptions of the new species are presented, together with notes on their chemistry, distribution, ecology and taxonomy. A key to all known species of Pseudopyrenula from India is also presented.

Three new species of thelotremoid lichens, Ampliotrema subglobosum Poengs. & Lumbsch, Ocellularia lichexanthonica Poengs. & Lumbsch and O. saxiprotocetrarica Poengs. & Lumbsch, are described and illustrated based on specimens from southern Thailand. Ampliotrema subglobosum is similar to A. globosum but differs by having larger ascospores with more septa. Ocellularia lichexanthonica differs from O. subdolichotata in ascomata diameter and by containing lichexanthone. Ocellularia saxiprotocetrarica is similar to O. gentingensis in ascospore length and the number of ascospore septa but has narrower ascospores and contains protocetraric acid. Fifteen species are reported for the first time for Thailand: Austrotrema bicinctulum (Nyl.) I. Medeiros et al., Baeomyces heteromorphus Nyl. ex C. Bab. & Mitt., Chapsa niveocarpa Mangold, Chiodecton sphaerale Ach., Erythrodecton malacum (Kremp.) G. Thor, Lecanora subjaponica L. Lü & H. Y. Wang, Leucodecton subcompunctum (Nyl.) Frisch, Myriotrema concretum (Fée) Hale, M. neoterebrans Frisch, Ocellularia khasiana (Patw. & Nagarkar) Kraichak et al., O. upretii S. Joshi et al., Pseudotopeliopsis scabiomarginata (Hale) Parnmen et al., Sulzbacheromyces sinensis (R. H. Petersen & M. Zang) Dong Liu & Li S. Wang, Thelotrema diplotrema Nyl., and T. isidiophorum (Kremp.) Zahlbr. Ampliotrema globosum (Hale) Poengs. & Lumbsch is proposed as a new combination. The genus Erythrodecton G. Thor is a new genus for the lichen flora of Thailand.

The pale yellowish tint of usnic acid in a lichen thallus itself is a commonly used character in identification keys, particularly in the genus Cladonia. Furthermore, the presence of usnic acid is phylogenetically significant in numerous groups of lichens. While the distinctive colour of usnic acid is readily visible when present in high concentrations, it is commonly problematic to discern when in low to moderate concentrations. We explored the use of an anisaldehyde reagent for visualizing usnic acid. Using both usnic acid-containing Cladonia samples and pure usnic acid, this reaction quickly yields a bright magenta colour on HPTLC and TLC plates after heating and directly with crude acetone extracts on glass slides heated with a lighter. The same magenta product was observed whether or not the usnic acid was accompanied by barbatic, fumarprotocetraric, psoromic, squamatic or thamnolic acids, each of which alone did not produce any colour with anisaldehyde reagent. However, the merochlorophaeic acids in C. albonigra also produced a red reaction. Analysis by high resolution LC-MS of the reaction mixture between anisaldehyde and usnic acid revealed several ions at m/z 477.1586 ([M+H]+, C27H25O8) and 463.1385 ([M+H]+, C26H23O8), respectively, consistent with aldol condensation of usnic acid and p-anisaldehyde.

Umbilicaria ahtii sp. nov. is described based on morphological and molecular characters. The new species resembles Umbilicaria vellea but the former has larger and submuriform ascospores, a darker lower surface, longer dark brown to black rhizinomorphs, and lacks thalloconidia directly on the lower surface and basal part of the rhizinomorphs. Phylogenetic analyses (ITS, mtLSU and RPB2) confirmed the distinctness of U. ahtii and indicated its sister relationship to U. meizospora. Umbilicaria ahtii is described from Finland and is currently known from several localities in Northern Europe (Svalbard, Norway, Finland, Kola Peninsula in Russia), Asia (Kodar Range, Siberia) and North America (Alaska). Within the U. vellea group, new molecular data confirmed U. koidzumii as a widespread, separate species sister to U. cinereorufescens. Diagnostic traits and variability of species, as well as their distribution patterns and nomenclature, are discussed.

During a recent expedition of the Eurasian Dry Grassland Group in the steppes of southern Ukraine, we discovered on sand dunes a new sterile crustose aspicilioid lichen with rhizomorphs. It is described here as new to science under the name Circinaria ucrainica (Megasporaceae). The new combination Circinaria reptans (Looman) Khodos. & Darmostuk is also proposed. Circinaria ucrainica is characterized by small grey areoles with a net of dark grey to brownish spicate prothalline tips and pale rhizomorphs. According to the phylogenetic analysis, the new species is closely related to the terricolous Circinaria reptans, but the latter has thicker rhizomorphs of 200–400 μm diameter, finely developed areoles and lacks spicate prothalline tips. Furthermore, we discuss the differences between the new species and other morphologically similar species with rhizomorphs, such as Aspicilia spicata, Circinaria crespiana and C. reptans. The ecological characters of soil and vegetation, including vascular plants, bryophytes and lichens, are provided for the habitat of C. ucrainica.

Calicium poculatum and Ramboldia canadensis are described as new species occurring on Larix laricina. Calicium poculatum, currently known from four Canadian provinces and the US state of Minnesota, is characterized by its short-stalked black ascomata, short ascospores and occurrence as a parasite on Lecanora caesiorubella subsp. saximontana. Based on DNA sequence data, its nearest relative is the likewise parasitic Calicium episcalaris. Ramboldia canadensis, currently known only from dead wood of Larix laricina snags in Canada, engages in a fully developed lichen symbiosis with Trebouxia simplex and is characterized in statu symbiotico by having a rimose to verrucose-areolate, greyish creamy sorediate thallus with dark brown to blackish soredia that begin on the margins, and the occurrence of a secondary metabolite similar to barbatolic acid. Phylogenetic analysis recovers it as sibling to a clade of the genus heretofore known only from the Southern Hemisphere and the lower latitudes of the Northern Hemisphere. We also report Lecidella xylophila as new to North America.

Seven species of Cliostomum Fr. recorded from Australia are treated. These include the widespread C. griffithii (Sm.) Coppins, the austral C. praepallidum (Müll. Arg.) Kantvilas & Fryday and the Tasmanian endemic C. vezdae Kantvilas, a reinstated name previously subsumed under C. flavidulum Hafellner & Kalb. Three species are described as new: C. latisporum Kantvilas, a corticolous species containing atranorin and gangaleoidin from coastal Tasmania and New South Wales, characterized by pale pink, soon immarginate apothecia, 0.3–0.9 mm wide, non-capitate, unpigmented paraphyses, and relatively wide, 1(–3)-septate ascospores, 9–15 × 4–6 μm; C. litorale Kantvilas, a saxicolous species containing atranorin and confluentic acid, recorded only from Tasmania, with relatively large, usually pale pinkish apothecia, 0.6–1.5 mm wide, non-capitate paraphyses, and 1(–2)-septate ascospores, 9–13 × 4−6 μm; and C. saxatile Kantvilas, a saxicolous species containing atranorin and lecanoric acid, also known only from Tasmania, with dark brown to black apothecia, 0.3–0.5 mm wide, pigmented with Laurocerasi-brown, capitate paraphyses, and 1-septate ascospores, 7–14 × 3–5 μm. The widespread, coastal Australasian species Tylothallia verrucosa (Müll. Arg.) Kantvilas is transferred to Cliostomum, with the additional synonym Catillaria brisbanensis Räsänen. Megalaria variegata (Müll. Arg.) D. J. Galloway, based on a New Zealand type, is a further synonym of Cliostomum griffithii. All species are illustrated and described on the basis of Australian and Tasmanian specimens.

Two new species of the genus Lecidella, one with a North American-maritime Antarctic distribution and one with a so far exclusively southern South American-maritime Antarctic distribution, are described using molecular and morphological tools. Lecidella ayazii is a species growing on soil and also on mosses and has so far been found on the Antarctic Peninsula, as well as in the alpine areas of the La Sal Mountains, Utah, USA and in the Kivalliq Region (Nunavut) in the north of Canada, whereas L. drakensis occurs mainly on siliceous rocks, rarely on mosses, and has been recorded on both sides of the Drake Passage in southern Patagonia and the Antarctic Peninsula. Phylogenetic analysis of the nrITS sequence data shows that both species belong in the L. elaeochroma clade, each forming a highly supported and distinct group. Furthermore, they also differ in morphological and chemical characters from the species described so far in this clade. In addition, five further accessions were recorded from the maritime Antarctic, which were placed in the cosmopolitan and heterogeneous L. stigmatea clade, of which one could be assigned to the bipolar species L. siplei.