Gene expression variation can be partitioned into different components (regulatory, genetic and acclimatory effects) but for lichen-forming fungi, the relative importance of each of these effects is unclear. Here, we studied gene expression in the lichen-forming fungus Lobaria pulmonaria in response to thermal stress and parasitism by the lichenicolous fungus Plectocarpon lichenum. Our experimental procedure was to acclimate lichen thalli to 4 °C over three weeks and then expose them to 15 °C and 25 °C for 2 hours each, sampling infected and visually asymptomatic thalli at each temperature. Quantitative Real-Time PCR was utilized to quantify gene expression of six candidate genes, normalizing expression values with two reference genes. We found that two genes encoding heat shock proteins (hsp88 and hsp98), two polyketide synthase genes (rPKS1, nrPKS3) and elongation factor 1-1-α (efa) were upregulated at higher temperatures. Moreover, we observed higher expression of hsp98 at 25 °C in samples infected by P. lichenum than in uninfected samples. Finally, in partial redundancy analyses, most of the explained variation in gene expression was related to temperature treatment; genetic variation and long-term acclimatization to sites contributed far less. Hence, regulatory effects (i.e. direct adjustments of gene expression in response to the temperature change) dominated over genetic and acclimatory effects in the gene expression variability of L. pulmonaria. This study suggests that L. pulmonaria could become a valuable lichen model for studying heat shock protein responses in vivo.

The Rostania occultata species complex (‘Collema occultatum s. lat.’) is revised in Fennoscandia and found to consist of four species, all epiphytes on deciduous trees: Rostania effusa A. Košuth., M. Westb. & Wedin sp. nov., R. occultata (Bagl.) Otálora et al., R. pallida A. Košuth., M. Westb. & Wedin sp. nov. and R. populina (Th. Fr.) A. Košuth., M. Westb. & Wedin comb. nov. Rostania effusa and R. pallida are newly described from humid habitats in old-growth boreal coniferous forests, usually with a mixture of deciduous trees, and from similar areas in the subalpine birch-dominated forests of Fennoscandia. Rostania effusa is characterized by apothecia with red-brown apothecium discs and an excipulum thallinum with a simple pseudocortex and cubic to oblong, muriform spores. Rostania pallida has apothecia with whitish to pale yellowish discs and an excipulum thallinum with a distinct cellular pseudocortex, and ellipsoid, muriform mature spores that are often constricted at the centre. A lectotype is designated for Collema quadratum J. Lahm ex Körb. The new combination Rostania populina is introduced for the species recognized until now as the variety Rostania occultata var. populina (Th. Fr.) Perlmutter & Rivas Plata. A key to the six species in Rostania s. str. is included.

To clarify deep relationships among species lineages within Bacidia s. str., and to investigate the robustness of the deeper branches, we combined data from three traditionally used RNA-coding genes (nrITS, nrLSU and mtSSU) with two protein-coding genes (RPB1 and RPB2). The multigene phylogeny contained 48 newly generated sequences from the Russian Far East and all Bacidia s. str. sequences from GenBank (131 sequences). We subjected the alignments for the single and concatenated data sets to Bayesian inference (BI) and two maximum likelihood (ML) analyses (RAxML and IQ-TREE). The topologies of phylogenetic trees recovered from BI and ML analyses were highly concordant. The multilocus phylogeny of Bacidia s. str. was congruent with previous results based on nrITS sequences from the Russian Far East but with considerably higher support values for most of the deeper branches. A correlation between the recovered clades and apothecial pigments in the upper part of the hymenium and lateral exciple was observed. Based on morphological and molecular evidence, Bacidia obtecta is described as new to science. It was recovered as the sister lineage of B. elongata. The two species are alike in having up to four enlarged lumina cells along the exciple edge, but B. obtecta differs in the abundant crystals found in the upper hymenium and lateral exciple, and by having spores with fewer septa.

To facilitate population-genetic studies, we developed simple sequence repeat (SSR) markers and a molecular species identification assay for Peltigera membranacea (Ascomycota, Peltigerales), a common ground-dwelling lichen of forest and tundra ecosystems. Additional markers were developed for its Nostoc photobiont. Twenty-one fungal markers for P. membranacea were found to be polymorphic, with the number of alleles ranging from 3–21. Nei's unbiased gene diversity ranged from 0.588 to 0.640 in four significantly structured (FST = 0.059) mycobiont populations. For the Nostoc photobiont, 14 polymorphic SSR were developed, yielding 4–14 alleles each, with gene diversity ranging from 0.062 to 0.771 in four populations showing substantial population structure (FST = 0.278). The new markers developed are suitable for population genetic studies of Peltigera membranacea and of its cyanobiont, and at the same time allowed us to distinguish 98.5% of P. membranacea specimens from morphologically similar species of Peltigera.

A review of algal (including cyanobacterial) symbionts associated with lichen-forming fungi is presented. General aspects of their biology relevant to lichen symbioses are summarized. The genera of algae currently believed to include lichen symbionts are outlined; approximately 50 can be recognized at present. References reporting algal taxa in lichen symbiosis are tabulated, with emphasis on those published since the 1988 review by Tschermak-Woess, and particularly those providing molecular evidence for their identifications. This review is dedicated in honour of Austrian phycologist Elisabeth Tschermak-Woess (1917–2001), for her numerous and significant contributions to our knowledge of lichen algae (some published under the names Elisabeth Tschermak and Liesl Tschermak).

The evolution of multicellularity paved the way for significant increases in biological complexity. Although multicellularity has evolved many times independently, we know relatively little about its origins. Directed evolution is a promising approach to studying early steps in this major transition, but current experimental systems have examined only a subset of the possible evolutionary routes to multicellularity. Here we consider egalitarian routes to multicellularity, in which unrelated unicellular organisms evolve to become a multicellular organism. Inspired by microbial syntrophies and lichens, we outline three such routes from a system of different species to an interdependent relationship that replicates. We compare these routes to contemporary experimental systems and consider how physical structure, the threat of invasion, division of labour and co-transmission affect their evolution.

Gibbosporina cyanea is described here as new to science, based on its holotype collected in Sri Lanka in the 1860s. The species is a bipartite cyanolichen in contrast to all other known Gibbosporina species, which are tripartites. The species appears to have evolved through cephalodia emancipation followed by divergence. Phyllidia indicate a cephalodiate evolutionary origin with a continued function similar to vegetative propagules. The species is considered to represent a relatively young speciation within an evolutionary old genus and G. sphaerospora is discussed as a possible candidate for being its closest known relative based on spore morphology. As the species appears to be so different from the remaining Gibbosporina species, it is compared here to representatives of other related palaeotropical cyanogenera, such as Leightoniella, Lepidocollema, Pannaria and Physma. Perispore structure is shown to be a useful character in separating these genera, including distinct clades of the non-monophyletic genera Physma and Lepidocollema. Leightoniella zeylanensis is reported here as new to Japan, and it is concluded that Pannaria lurida needs to be restudied in India and Sri Lanka.

The new species Aspicilia malvinae is described from the Falkland Islands. It is the first species of Megasporaceae to be discovered on the islands and only the seventh to be reported from South America. It is distinguished from other species of Aspicilia by the unusual secondary metabolite chemistry (hypostictic acid) and molecular sequence data. The collections of the new species support two lichenicolous fungi: Endococcus propinquus s. lat., which is new to the Falkland Islands, and a new species of Sagediopsis with small perithecia and 3-septate ascospores c. 18–20 × 4–5 μm, which is described here as S. epimalvinae. A total of 60 new DNA sequences obtained from species of Megasporaceae (mostly Aspicilia) are also introduced.

Epiphytic lichens are sensitive to deteriorating air quality, but levels of nitrogen and especially sulphur deposition have been in decline over most of Europe in recent decades. We assessed the response of epiphytic lichens to this decline, using data from long-term monitoring sites in Sweden. We analyzed 20 years of data to investigate temporal trends in lichen communities’ sensitivity to sulphur, nitrogen preference, species richness and alpha and beta diversity. We found only limited and partial evidence of recovery in the area that previously had high levels of deposition, and a decline in mean sulphur sensitivity at a northern site with low deposition levels throughout the monitoring period. The slow recolonization of sensitive species, even where environmental conditions are now suitable, is probably a result of impoverished regional species pools and the inherent limited dispersal capacity of many lichen species. We suggest due consideration of these factors in the use of epiphytic lichens as environmental indicators in a period of improving air quality.

In recent years, several species that have long been considered to belong in Bacidia s. lat. have been transferred to other genera such as Bellicidia, Bibbya, Scutula, and also to Toniniopsis, accommodating species previously placed in Bacidia and Toninia. One of its widespread species, Toniniopsis subincompta, can be recognized by its thinly granular thallus, dark brown to black apothecia, green epithecium, red-brown hypothecium, and bacilliform ascospores. However, it shows considerable variation in thallus structure, and coloration of apothecia, hypothecium and exciple. We sequenced 20 specimens of T. subincompta to investigate whether there is phylogenetic support for the delimitation of species in accordance with the variability of the observed characters. For phylogenetic analyses, we used newly generated sequence data from the nuclear internal transcribed spacer (nrITS), mitochondrial small subunit (mtSSU) and DNA-directed RNA polymerase II subunit (RPB2). Maximum likelihood and Bayesian inference analyses, as well as three species delimitation programs, provided consistent evidence that T. subincompta forms two separate lineages, to be recognized at the species level. The complex nomenclature of T. subincompta (basionym Lecidea subincompta) shows it to be a synonym of Bellicidia incompta. For the most common taxon previously called Bacidia (Toniniopsis) subincompta, the new combination T. separabilis is made, rather than proposing a conserved type for Lecidea subincompta. Toniniopsis dissimilis is newly described to accommodate the less common taxon. Toniniopsis dissimilis is characterized by a predominantly wrinkled to warted to subsquamulose thallus; generally grey-brown to dark brown apothecia, often with a lighter margin; a dark brown hypothecium, frequently gradually merging into the coloration of the exciple below and the lateral part of the exciple attached to the hymenium; a mostly colourless rim and lateral part of the exciple. The closely related T. separabilis is characterized by a thallus of mostly single or contiguous ±loose granules, often forming short, coralloid, isidium-like bulges; darker apothecia, with a margin mostly of the same colour or darker than the disc; a comparatively thinner hypothecium easily separated from the exciple below. The rim and lateral part of the exciple often contain either a blue, brown or mixed blue-brown colour in the upper part or along the whole margin. Lectotypes of Bacidia vegeta, Lecidea bacillifera f. melanotica and Secoliga atrosanguinea var. affinis (the synonyms of T. separabilis) are selected. Cyanotrophy and the occurrence of albino morphs in T. separabilis are discussed.

Peter D. Crittenden served as senior editor of The Lichenologist, the flagship journal in the field of lichenological research, for a period of two decades, between 2000 and 2019. A review of the development of the journal and the publication output during this period is provided. The number of papers published during this period (1197) matches that of all papers published under the three previous senior editors, Peter W. James, David L. Hawksworth and Dennis H. Brown, during a much longer period of 42 years from 1958 to 1999. Peter oversaw important editorial changes to the layout and content of the journal: an increased size with a modern cover design, leaving behind the classic mint-coloured cover of more than 40 years; the addition of ‘thematic issues’ and encouragement of large monographs; implementation of substantial changes to the Code, such as effective electronic publication and obligate registration of new fungal names; and more recently a new policy to reject so-called ‘single naked species descriptions’. Shortly before Peter took over as senior editor, The Lichenologist had received its first impact factor, and Peter managed to continuously increase this measure from around 0.9 to lately up to over 1.5, higher than most other competing journals. The 1197 papers between 2000 and 2019 were published by a total of 1138 different authors, more than half of whom appeared just once as author, whereas a small number participated in numerous (up to 93) papers. There was a continuous increase in the mean number of authors per paper per year, from below 2.5 to around 3.5, the highest numbers ranging between 11 and 30; still, c. 75% of all papers between 2000 and 2019 were single-authored or had up to three authors. Based on affiliations at the time of publication, two thirds of author contributions came from Europe (66%), 13% from North America, 9% from Asia and 7% from Latin America. Likewise, almost half of the study areas were located in Europe and around 10% each in North America, South America and Asia. The countries with the highest number of studies included, in descending order, the United States, Spain, the United Kingdom, Norway and Sweden. North America and Europe were over-represented in terms of author contributions, whereas Africa, Latin America, Australia and Oceania were over-represented in terms of study areas. The 1197 papers analyzed encompassed a broad diversity of topics, classified into 32 categories. Taxonomy of lichenized fungi was the most frequent component, representing the focal point in almost half of all studies, followed by phylogeny and evolution, ecology, and the taxonomy of lichenicolous fungi. Around two thirds of the currently accepted genera of lichenized fungi were treated, with a significant correlation between known species richness and the number of papers in which a genus was treated, underlining the taxonomic representativity of papers published in the journal during the past two decades. Examples of genera that were treated more frequently than expected included commonly studied model organisms, such as Lobaria, and those frequently featured in ecological or other non-taxonomic studies, such as Xanthoria. Species-rich tropical genera, particularly in the Graphidaceae, were generally under-represented. Mean number of authors per paper per volume and total number of country origins of authors per volume were the best predictors of impact factor, followed by diversity of study countries per volume, mean number of study countries per paper per volume, mean number of topics per paper per volume, and proportion of studies with phylogenetic components per volume. Individual papers that contributed to high impact factors included broad-scale revisionary treatments and worldwide keys to species-rich taxa, substantial phylogenetic reclassifications of known taxonomic groups, papers dealing with novel methodological approaches of broad interest, and broad-scale studies related to environmental change and lichen biomonitoring.

The taxonomy of the genus Sticta in Hawaii is reassessed, based on a separately published molecular phylogeny using the fungal barcoding marker ITS. Based on Magnusson and Zahlbruckner's treatment from 1943 and Magnusson's catalogue from 1955, seven species of Sticta and three infraspecific taxa had been reported from the archipelago, all widespread except the putative endemic S. plumbicolor. Here we provide a taxonomic treatment of 13 taxa, 12 species and one subspecies, distinguished in a previous phylogenetic analysis: S. acyphellata, S. andina, S. antoniana, S. emmanueliana, S. flynnii, S. fuliginosa, S. hawaiiensis, S. limbata, S. plumbicolor, S. scabrosa subsp. hawaiiensis, S. smithii, S. tomentosa and S. waikamoi. All taxa are described, discussed and illustrated and a dichotomous key is presented. The implications of revised species taxonomies for studies in other fields such as ecology, ecophysiology, biogeography, biochemistry, and applications such as environmental monitoring are discussed. We also propose a protocol to use Sticta lichens to monitor the environmental health of Hawaiian ecosystems.

The lichenicolous ‘heterobasidiomycetes’ belong in the Tremellomycetes (Agaricomycotina) and in the Pucciniomycotina. In this paper, we provide an introduction and review of these lichenicolous taxa, focusing on recent studies and novelties of their classification, phylogeny and evolution. Lichen-inhabiting fungi in the Pucciniomycotina are represented by only a small number of species included in the genera Chionosphaera, Cyphobasidium and Lichenozyma. The phylogenetic position of the lichenicolous representatives of Chionosphaera has, however, never been investigated by molecular methods. Phylogenetic analyses using the nuclear SSU, ITS, and LSU ribosomal DNA markers reveal that the lichenicolous members of Chionosphaera form a monophyletic group in the Pucciniomycotina, distinct from Chionosphaera and outside the Chionosphaeraceae. The new genus Crittendenia is described to accommodate these lichen-inhabiting species. Crittendenia is characterized by minute synnemata-like basidiomata, the presence of clamp connections and aseptate tubular basidia from which 4–7 spores discharge passively, often in groups. Crittendenia, Cyphobasidium and Lichenozyma are the only lichenicolous lineages known so far in the Pucciniomycotina, whereas Chionosphaera does not include any lichenicolous taxa.

Usnic acid is a unique lichen metabolite of industrial importance, widely studied to explore its pharmacological potential and valued especially as an antibacterial agent in cosmetics. Although a vast number of papers describe usnic acid extraction from various lichen species, none has so far provided an unequivocal indication of the best extraction procedure for this compound. Thus, the current study was focused on the direct comparison of three commonly used usnic acid extraction methods (heat reflux, shaking, ultrasound-assisted extractions), which were optimized using fractional factorial design. Heat reflux extraction, shaking extraction and ultrasound-assisted extraction were first optimized in a series of experiments using fractional factorial design, with respect to three parameters: the extraction time, the solvent used and the number of extraction repetitions. HPLC was employed for usnic acid quantitative analysis. The best scores for each extraction method were statistically compared and the optimal conditions were indicated. The optimal set of parameters for usnic acid was established to be a single, 60 min heat reflux extraction with acetone. This extraction scheme provided 4.25 ±0.08 mg g−1 d.w. of usnic acid, while for ultrasound-assisted and shaking extractions the amount was two- or even four times lower (2.33 ±0.17 and 0.97 ±0.08 mg g−1 d.w., respectively). The optimal procedure for usnic acid extraction described here may be suitable for effective acquisition of this compound for scientific research purposes, but also for applications in the pharmaceutical or cosmetic industries.

The new species Psoroma capense and P. esterhuyseniae are described from four alpine localities in the Western Cape Province of South Africa and are the only known Psoroma species from Africa. The specimens were all collected from moist sites near watercourses, on cool and mostly south-facing cliffs. Psoroma capense resembles P. tenue in gross morphology but differs in the ascending thallus squamules, lack of secondary compounds and short-ellipsoid to ovoid ascospores. However, a phylogenetic analysis involving the markers ITS, nucLSU, mtSSU and Mcm7, comparing the only recent collection of P. capense with previously published sequences, shows that it belongs to the P. hypnorum lineage, with no known, closely related species. Psoroma esterhuyseniae resembles P. hypnorum but has subglobose to short-ellipsoid ascospores without apical perispore extensions. The two species are thought to have evolved from one or two long-distance dispersal events during the Pleistocene.

Fruticose lichens of the genus Usnea Dill. ex Adans. (Parmeliaceae), generally known as beard lichens, are among the most iconic epiphytic lichens in modern forest ecosystems. Many of the c. 350 currently recognized species are widely distributed and have been used as bioindicators in air pollution studies. Here we demonstrate that usneoid lichens were present in the Palaeogene amber forests of Europe. Based on general morphology and annular cortical fragmentation, one fossil from Baltic amber can be assigned to the extant genus Usnea. The unique type of cortical cracking indirectly demonstrates the presence of a central cord that keeps the branch intact even when its cortex is split into vertebrae-like segments. This evolutionary innovation has remained unchanged since the Palaeogene, contributing to the considerable ecological flexibility that allows Usnea species to flourish in a wide variety of ecosystems and climate regimes. The fossil sets the minimum age for Usnea to 34 million years (late Eocene). While the other similar fossils from Baltic and Bitterfeld ambers cannot be definitely assigned to the same genus, they underline the diversity of pendant lichens in Palaeogene amber forests.

Saxicolous, lecideoid lichenized fungi have a cosmopolitan distribution but, being mostly cold adapted, are especially abundant in polar and high-mountain regions. To date, little is known of their origin or the extent of their trans-equatorial dispersal. Several mycobiont genera and species are thought to be restricted to either the Northern or the Southern Hemisphere, whereas others are thought to be widely distributed and occur in both hemispheres. However, these assumptions often rely on morphological analyses and lack supporting molecular genetic data. Also unknown is the extent of regional differentiation in the southern polar regions. An extensive set of lecideoid lichens (185 samples) was collected along a latitudinal gradient at the southern end of South America. Subantarctic climate conditions were maintained by increasing the elevation of the collecting sites with decreasing latitude. The investigated specimens were placed in a global context by including Antarctic and cosmopolitan sequences from other studies. For each symbiont three markers were used to identify intraspecific variation (mycobiont: ITS, mtSSU, RPB1; photobiont: ITS, psbJ-L, COX2). For the mycobiont, the saxicolous genera Lecidea, Porpidia, Poeltidea and Lecidella were phylogenetically re-evaluated, along with their photobionts Asterochloris and Trebouxia. For several globally distributed species groups, the results show geographically highly differentiated subclades, classified as operational taxonomical units (OTUs), which were assigned to the different regions of southern South America (sSA). Furthermore, several small endemic and well-supported clades apparently restricted to sSA were detected at the species level for both symbionts.

Lichens are widely acknowledged to be a key component of high latitude ecosystems. However, the time investment needed for full inventories and the lack of taxonomic identification resources for crustose lichen and lichenicolous fungal diversity have hampered efforts to fully gauge the depth of species richness in these ecosystems. Using a combination of classical field inventory and extensive deployment of chemical and molecular analysis, we assessed the diversity of lichens and associated fungi in Glacier Bay National Park, Alaska (USA), a mixed landscape of coastal boreal rainforest and early successional low elevation habitats deglaciated after the Little Ice Age. We collected nearly 5000 specimens and found a total of 947 taxa, including 831 taxa of lichen-forming and 96 taxa of lichenicolous fungi together with 20 taxa of saprotrophic fungi typically included in lichen studies. A total of 98 species (10.3% of those detected) could not be assigned to known species and of those, two genera and 27 species are described here as new to science: Atrophysma cyanomelanos gen. et sp. nov., Bacidina circumpulla, Biatora marmorea, Carneothele sphagnicola gen. et sp. nov., Cirrenalia lichenicola, Corticifraga nephromatis, Fuscidea muskeg, Fuscopannaria dillmaniae, Halecania athallina, Hydropunctaria alaskana, Lambiella aliphatica, Lecania hydrophobica, Lecanora viridipruinosa, Lecidea griseomarginata, L. streveleri, Miriquidica gyrizans, Niesslia peltigerae, Ochrolechia cooperi, Placynthium glaciale, Porpidia seakensis, Rhizocarpon haidense, Sagiolechia phaeospora, Sclerococcum fissurinae, Spilonema maritimum, Thelocarpon immersum, Toensbergia blastidiata and Xenonectriella nephromatis. An additional 71 ‘known unknown’ species are cursorily described. Four new combinations are made: Lepra subvelata (G. K. Merr.) T. Sprib., Ochrolechia minuta (Degel.) T. Sprib., Steineropsis laceratula (Hue) T. Sprib. & Ekman and Toensbergia geminipara (Th. Fr.) T. Sprib. & Resl. Thirty-eight taxa are new to North America and 93 additional taxa new to Alaska. We use four to eight DNA loci to validate the placement of ten of the new species in the orders Baeomycetales, Ostropales, Lecanorales, Peltigerales, Pertusariales and the broader class Lecanoromycetes with maximum likelihood analyses. We present a total of 280 new fungal DNA sequences. The lichen inventory from Glacier Bay National Park represents the second largest number of lichens and associated fungi documented from an area of comparable size and the largest to date in North America. Coming from almost 60°N, these results again underline the potential for high lichen diversity in high latitude ecosystems.

Species conservation depends on accurate data, but for many lichens existing collections are geographically biased and contain many taxonomic errors. It is unclear whether ‘non-expert’, systematic monitoring schemes can address these sources of error, particularly for taxonomically challenging lichens (e.g. species requiring chemistry for accurate identification). In this case study we use the Alberta Biodiversity Monitoring Institute (ABMI), a large-scale, systematic, multi-taxon monitoring programme, to better understand the ecology and distribution of a putative rare species, Cladonia rei. Collections of C. rei from Alberta dating from 1947 suggested the species was broadly distributed but rare, with seven accessioned specimens. We used comparative morphology, thin-layer chromatography and habitat modelling to compare historical records against more recent material from ABMI surveys. Contrary to the historical collections, ABMI samples suggest C. rei is almost entirely limited to the dry mixed grassland, northern fescue grassland and aspen parkland natural regions, and that within these ecosystems it is relatively common. The typical ecotype exhibited included a persistent primary thallus, podetia with a persistent basal cortex, and secondary squamules; typically they lacked cups, well-developed apothecia and fumarprotocetraric acid, and ramifications were sparse. Cladonia rei was consistently found in pastures and undisturbed grasslands that hosted relatively rich communities of epigeic lichens, thus it does not appear to act as a pioneer in Alberta or to commonly occupy the anthropogenic niches documented elsewhere. In summary, large-scale, systematic, non-targeted monitoring employing novices redressed issues of sample bias through almost 300 C. rei collections, simultaneously improving the ecological understanding of a putative rare species.