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.

Cladonia sandstedei forms cushion-shaped lichens that colonize open environments and is distributed throughout the Caribbean and the south-eastern United States. It co-occurs in parts of its range with C. subtenuis, a morphologically similar taxon that is distinguished from the former by the presence of usnic acid. Preliminary phylogenetic analysis with the RPB2 and TEF-1α loci revealed that these taxa were closely related, but relationships were inconsistent among markers. Here, we combined phylogenetic and population genomic analyses based on RADseq data to clarify the evolutionary relationships and phylogeography of these taxa. Both approaches indicate that the taxa cannot be separated based on secondary metabolites, as previously proposed, but instead form a complex composed of several lineages, largely unrelated to chemistry but with a strong geographical structure in their genetic variation. Continental populations formerly separated under the names C. sandstedei and C. subtenuis were closely related to each other. A similar pattern was observed in the Jamaican counterparts of these taxa, suggesting homoplasy of secondary chemistry. Discriminant Analysis of Principal Components (DAPC) hinted at potential conspecificity between populations in Cuba and Puerto Rico on one hand, and between Jamaica and the continental US on the other; however, phylogenetic analysis and other population-level analyses (PCA and fineRADstructure) suggested that both insular and continental populations were more likely to be reproductively isolated from each other. Based on this, we propose to recognize only one species for the entire complex, under the older name C. sandstedei, with the four spatially structured clades as subspecies: C. sandstedei subsp. sandstedei (restricted to Jamaica) and C. sandstedei subsp. subtenuis comb. nov. (restricted to continental North America) exhibit several chemosyndromes variably containing usnic acid and/or atranorin. The two additional subspecies described here as new, C. sandstedei subsp. cubana and C. sandstedei subsp. landroniana, exhibit the atranorin chemosyndrome and are restricted to Cuba and Puerto Rico, respectively. Our work reaffirms the power of combining RADseq-based phylogenetics and population genetics to disentangle taxonomic and evolutionary histories in poorly understood, closely related and phenotypically similar lichen-forming fungal species.

The Cladonia cervicornis group comprises lichen-forming fungi characterized by having scyphi with central proliferations. It includes c. 20 species globally. The taxonomy of this group is poorly resolved, with many species not thoroughly disentangled. The focus of this study is the European species in the C. cervicornis group. In order to estimate the phylogenetic relationships of these species, six loci were used: ITS rDNA, IGS rDNA, RPB1, RPB2, ef1α and cox1. Species delimitation methods (ASAP, PTP and GMYC) were used to infer the species boundaries based on four loci, ITS rDNA, IGS rDNA, cox1 and RPB2. A morphological analysis based on multivariate methods was performed to assess the importance of phenotypic differences among the lineages. The phylogenetic reconstructions placed the species of this group in the subclade Cladonia. Five lineages were recovered, corresponding to C. cervicornis, C. macrophyllodes, C. pulvinata, C. verticillata and a new lineage that we describe here, C. teuvoana. Our analyses revealed that Cladonia cineracea, C. stricta and C. trassii are polyphyletic.

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.

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.

Candelariella ahtii Yakovchenko sp. nov. is described based on phenotypic and ITS nrDNA sequence data. The species, occurring on soil in the crevices and cracks of siliceous rocks, is characterized by its squamulose cushion-forming thallus of imbricate, rounded to weakly incised granules/squamules with a greenish yellow to pale yellow pulverulent upper surface, lecanorine apothecia with a plane to somewhat convex ochre-yellow disc and a permanent thick thalline margin, 8-spored asci and ellipsoid to narrowly ellipsoid ascospores with rounded ends, as well as a distribution in Central and North-East Asia. It is similar to Candelariella citrina but differs in having ascospores without attenuated ends and smaller squamules. Candelariella citrina is excluded from the lichen flora of Russia. A worldwide key to all known Candelariella species with 8-spored asci, including 41 names, 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.

Sixteen species and two varieties of lichenicolous fungi are reported from Rhizoplaca s. lat. Four species and one variety are described as new to science: Caeruleoconidia ahtii Zhurb. (on Rhizoplaca s. str.), with hyaline to pale greyish turquoise, comparatively large conidia; Cercidospora mongolica Zhurb. & Cl. Roux (on Rhizoplaca s. str.), with a reddish brown (above) to pale brownish grey to colourless (below) exciple, mostly 4-spored asci, and (0‒)1(‒2)-septate ascospores, mostly 23‒28.5 μm long; C. tyanshanica Zhurb. & Cl. Roux (on Protoparmeliopsis and Rhizoplaca s. str.), with a uniformly grey exciple, mostly 4-spored asci, and (0‒)1(‒2)-septate ascospores, mostly 25.5‒31.5 μm long; Stigmidium pseudosquamariae Zhurb. (on Protoparmeliopsis), inducing brown cerebriform galls, with consistently immersed ascomata and well-developed pseudoparaphyses of type b sensu Roux & Triebel (1994); and Arthonia clemens var. peltatae Zhurb. (on Protoparmeliopsis), with a brown epihymenium without grey shade. An unidentified species of Leptosphaeria growing on Protoparmeliopsis peltata, and Lichenostigma cf. chlaroterae growing on P. peltata and Rhizoplaca chrysoleuca are briefly characterized. Arthonia clemens is newly reported for Kazakhstan, Kyrgyzstan and the Republic of Sakha (Yakutia) in Russia; Cercidospora melanophthalmae is new to Kazakhstan, Kyrgyzstan and Mongolia; Didymocyrtis rhizoplacae is new to Russia; Lichenoconium lecanorae and Muellerella erratica are new to Kyrgyzstan; Stigmidium squamariae s. lat. is new to Kazakhstan, Kyrgyzstan and Turkmenistan. Didymocyrtis rhizoplacae is documented for the first time on Rhizoplaca subdiscrepans, and Pyrenidium actinellum s. lat. on Protoparmeliopsis. A key to 36 species of lichenicolous fungi and lichens known to occur on Rhizoplaca s. lat. is provided.

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.