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.

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.

We investigated the influence of availability as well as type of organic substrate on the growth of the cyanolichen Peltigera membranacea. A total of 145 lichen lobes were grown in a plant growth chamber for 28 days. Of these, 73 were kept in permanent darkness and another 72 were exposed to a diurnal light-dark cycle. A third of the lobes from both treatments were grown on pulverized leaf litter, the second third on pulverized bryophytes, and the remainder were grown without an organic substrate to serve as a control group. Growth was quantified via relative growth rate, relative thallus area growth rate, and changes in specific thallus mass. The lobes kept in a diurnal light-dark cycle showed higher growth rates than those kept in darkness, as is expected for an organism that obtains its carbon from its photoautotrophic symbiosis partner. Furthermore, growth rates were higher in lobes growing on organic substrates. The results show that the availability of an organic substrate positively affects lichen growth in a growth cabinet. Leaf litter led to a higher biomass gain in lichen lobes, whereas area gain was unrelated to substrate type.

We present a robust, five-locus phylogeny of the Megasporaceae and, based on this, propose several taxonomic innovations. The new genus Antidea is erected for Aspicilia brucei, which occupies a position near the base of the phylogeny, and the new species Aspicilia indeterminata and A. suavis are described from Montana. We also show that all North American (and some European) records of Aspilidea myrinii are misidentifications with many representing a second species in the genus, differing from A. myrinii by having elevated apothecia and narrower ascospores and for which we make the new combination Aspilidea subadunans. Finally, we make the new combinations Lobothallia determinata and L. peltastictoides, and report the lichenicolous fungus Sagediopsis aspiciliae (on A. subadunans) as new to North America.

National Red Lists are useful tools in establishing local conservation priorities. The threat status of Estonian lichens based on the IUCN system has been assessed twice, in 2008 and 2023. In the latest Red List, the proportion of species of elevated conservation concern, that is taxa belonging to the Near Threatened and threatened categories or having become regionally extinct in Estonia, was high (58%) while Least Concern (LC) species represented one-third (36%) of all taxa. Macrolichens were more threatened than microlichens. The Red List Index (RLI), illustrating the trends of species in their projected extinction risk, was calculated. The values were low (< 0.7 in 2023), thus indicating a heightened risk both for the set of all species and for macrolichens. More than half of all Estonian lichens are associated with woodlands and 54% of these species are of elevated conservation concern. Lichens preferring broad-leaved deciduous trees included more threatened than LC species, while among lichens preferring other deciduous or coniferous trees the proportion of LC species was higher than that of threatened taxa. Lichens inhabiting calcareous grasslands had the highest share (69%) of taxa of elevated conservation concern. Comparisons of national red-listed data with four selected countries (Czech Republic, Denmark, Finland and Sweden) revealed that the biggest overlaps of Estonian taxa of elevated conservation concern were with the Czech Republic and Finland.

Seven new species of Verrucaria are described from Finland: Verrucaria hakulinenii sp. nov., V. juumaensis sp. nov., V. linkolae sp. nov., V. lohjaensis sp. nov., V. norrlinii sp. nov., V. oulankajokiensis sp. nov., and V. vainioi sp. nov. Verrucaria linkolae is also reported from the Czech Republic, Germany and the United Kingdom, V. norrlinii from Norway and V. juumaensis from Canada based on a previously unidentified soil sample. Based on ITS sequences, V. hakulinenii and V. juumaensis probably belong to the Verrucaria hydrophila group whereas V. linkolae, V. norrlinii, V. oulankajokiensis and V. vainioi are closely related to V. hunsrueckensis and V. nodosa. The new species are characterized by a thin brown or green thallus, rather small perithecia and a predominantly thin involucrellum reaching the exciple base level. Verrucaria hakulinenii is characterized by a thin thalline cover of the perithecia, a green thallus and fairly large spores (18–22 × 8–10 μm). Verrucaria juumaensis, V. linkolae, V. norrlinii and V. vainioi are characterized by a predominantly brown thallus, often with goniocyst-like units. Verrucaria linkolae has densely occurring perithecia (100–330 perithecia per cm2) whereas in V. juumaensis, V. norrlinii and V. vainioi perithecia occur more sparsely (40–160 perithecia per cm2). Verrucaria juumaensis and V. vainioi usually have a minute thallus. Verrucaria juumaensis differs from V. vainioi by slightly larger perithecia (0.18–0.27 mm diam.) and longer and wider spores. Verrucaria lohjaensis is characterized by a mosaically dark brown and white, small areolate thallus and conspicuous ostioles. Verrucaria oulankajokiensis has small perithecia that are often thinly covered by thalline tissue and a thallus partly surrounded by dark lines. Most species occur on calcareous rocks, but V. vainioi is restricted to siliceous rocks. Verrucaria linkolae and V. norrlinii are widely distributed both on calcareous, serpentine and siliceous rocks, preferring pebbles. Epiphytic occurrences of V. linkolae and V. norrlinii are confirmed. A key to the new species and species with a similar morphology in Finland is provided.

A lichenicolous species, Calicium ramboldiicola, growing on Ramboldia elabens is described. In phylogenetic analyses with 22 Calicium taxa, based on 121 sequences from five DNA regions (mtSSU, Mcm7, nuITS, nuLSU, β-tubulin), the new species formed a strongly supported clade with C. abietinum and C. verrucosum. Although the ascomata of the new species resemble miniatures of those of C. abietinum, no morphological synapomorphies for this clade were found. Calicium ramboldiicola is known from boreal and hemiboreal areas of northern Europe and north-eastern North America. It is the second known lichenicolous species of Calicium and the first found on a lichen in the Lecanorales.

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.

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.

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.

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.

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.

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.

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.

Sticta canariensis is a lichen which is rare in all parts of its range in Atlantic Europe and Macaronesia, where it occurs in laurisilva forests, a habitat highly threatened by global change. Thus, this species is of high priority for inclusion in conservation programmes where genetic diversity should be considered. We have established new microsatellite loci and generated a dataset that demonstrates the genetic diversity of the lichen-forming fungus S. canariensis from eight locations across its disjunct range, in Macaronesia, Norway and England. We genotyped 25 microsatellite loci for 65 specimens and detected five genetic clusters which resemble major geographical divisions, specifically among the Macaronesian archipelagos. The total number of observed alleles ranged from 2 to 22. These are the first microsatellite markers developed for S. canariensis and they will be useful for population genetic studies and for conservation assessments.

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.

We present a novel identification tool called PhyloKey, based on the method of morphology-based, phylogenetic binning developed within the software package RAxML. This method takes a reference data set of species for which both molecular and morphological data are available, computes a molecular reference tree, maps the morphological characters on the tree, and computes weights based on their level of consistency versus homoplasy using maximum likelihood (ML) and maximum parsimony (MP). Additional units for which only morphological data are known are then binned onto the reference tree, calculating bootstrap support values for alternative placements. This approach is modified here to work as an identification tool which uses the same character coding approach as interactive keys. However, rather than identifying individual samples through a progressive filtering process when entering or selecting characters, query samples are binned in batch mode to all possible alternative species in the tree, with each placement receiving a bootstrap support adding to 100% for all alternative placements. In addition to the fact that, after scoring a character matrix, a large number of specimens can be identified at once in short time, all possible alternative identifications are immediately apparent and can be evaluated based on their bootstrap support values. We illustrate this approach using the basidiolichen genus Cora, which was recently shown to contain hundreds of species. We also demonstrate how the PhyloKey approach can aid the restudying of herbarium samples, adding further value to these collections and contributing with large quantitative data matrices to ‘non-molecular museomics’. Our analysis showed that PhyloKey identifies species correctly with as low as 50% of the characters sampled, depending on the nature of the reference tree and the character weighting scheme. Overall, a molecular reference tree worked best, but a randomized reference tree gave more consistent results, whereas a morphological reference tree performed less well. Surprisingly, even character weighting gave the best results, followed by parsimony weighting and then maximum likelihood weighting.

iNaturalist is a widely-utilized platform for data collection and sharing among non-professional volunteers and is widely employed in citizen science. This platform's data are also used in scientific studies for a wide range of purposes, including tracking changes in species distribution, monitoring the spread of alien-invasive species, and assessing the impacts of urbanization and land-use change on biodiversity. Lichens, due to their year-round presence on trees, soil and rocks, and their diverse shapes and colours, have captured the attention of iNaturalist users, and lichen records are widely represented on the platform. However, due to the complexity of lichen identification, the use of data collected by untrained, or poorly trained volunteers in scientific investigation poses concerns among lichenologists. To address these concerns, this study assessed the reliability of lichen identification by iNaturalist users by comparing records on the platform with identifications carried out by experts (experienced lichenologists) in three cities where citizen science projects were developed. Results of this study caution against the use of unchecked data obtained from the platform in lichenology, demonstrating substantial inconsistency between results gathered by iNaturalist users and experts.

The new genus Nimisora Pérez-Ort., M. Svenss. & J. C. Zamora is introduced to accommodate a puzzling lecideoid epiphyte common in the central Iberian Peninsula. Nimisora is characterized by the following combination of characters: lecideoid apothecia, excipulum composed of sparingly branched radiating hyphae with narrow lumina, thick walls and swollen terminal cells, the presence of a brown K+ olivaceous green pigment in the epihymenium, an ascus tip similar to the Bacidia-type, and the presence of simple ellipsoid ascospores. Molecular analyses based on nrITS, nrLSU and mtSSU sequences unequivocally place the new genus within the Lecanoraceae; however, its phylogenetic affinities with other genera of the family remain largely unresolved. Comparisons with the morphologically closest genera are provided. The single species of the genus, Nimisora iberica Pérez-Ort., Turégano, M. Svenss. & J. C. Zamora sp. nov., is also described as new to science.