Fast-growing hybrid aspen has been widely planted on former agricultural lands in Northern and Eastern Europe to produce pulpwood and sequester carbon into woody biomass. The biodiversity of mature hybrid aspen plantations has so far been rarely analysed. Moreover, the potential of hybrid aspen plantations to host flora typical of European aspen stands – recognised as biodiversity hotspots in Eurasian boreal forests – has not been evaluated. This study focused on two organism groups with contrasting habitat preferences – ground-dwelling herbs and epiphytic lichens. We sought to clarify how environmental and landscape factors influenced the diversity of herbs, lichens, and species characteristic of European aspen stands (EA species). Data were collected across 42 study plots within 20 hybrid aspen plantations in Estonia. Altogether, 162 herb species and 65 lichens were recorded, including 92 species also found in European aspen stands. The proportion of EA species was higher among lichens (86.2%) than among herbs (22.2%), reflecting a stronger legacy effect of former agricultural land-use on ground-dwelling species than on epiphytes. Responses of herb and lichen diversity to environmental variables differed. Richness of herbs was related to litter and stand characteristics. Compositional analyses also highlighted the role of soil-litter variables and stand structure in herb composition. Lichens responded to landscape-related variables. A greater extent of older forests around the study plots increased the richness of EA species. In conclusion, mature hybrid aspen plantations are relatively species-rich and can enhance landscape connectivity for forest species, particularly epiphytes, in agricultural landscapes.

ABSTRACT Aim Fungi show a variety of reproductive strategies, switching between haploid and diploid forms to benefit from both, the acquisition of genetic variability through sexual reproduction and rapid population growth via asexual reproduction. Throughout the history of lichenology, lichen reproductive modes (e.g., soredia, isidia, apothecia) have been considered as important characters to circumscribe species. This includes the globally vulnerable lichen genus Cetrelia , where morphologically similar taxa with differing reproductive strategies were regarded as ‘species pairs’. We aim to test the historical species concept and evaluate factors responsible for the expression of differing fungal reproductive modes in the lichen genus Cetrelia . Location Global, covering Nearctic, Palearctic and Indomalayan biogeographic realms. Methods The morphology and chemistry of 601 samples representing 18 species were examined under the microscope and using thin‐layer chromatography. The Cetrelia species concept was assessed by multi‐locus phylogenetic analyses (nrITS‐IGS‐RPB1‐MCM7) based on maximum likelihood and Bayesian inference approaches. The correlation of reproductive traits, lichenized fungal and algal genetic identity, macroclimate, geography, habitat, secondary metabolites and substrate were evaluated using principal component analysis and variance partitioning analyses. Results The phylogenetic analyses indicate that ‘species pairs’ in Cetrelia are genetically indistinguishable, and primarily sexually reproducing species form a monophyletic clade with their counterpart. Variance partitioning analyses suggest that the reproductive modes of Cetrelia are driven by macroclimate, mycobiont, geography, photobionts and habitat. Main Conclusions Our work highlights the potential risks of climate change, especially the change of precipitation regimes affecting lichen reproduction and dispersal and the need to conserve habitats in south‐east Asia where the lichen genus Cetrelia diversity is largely restricted to.

Silver birch (Betula pendula) and hybrid aspen (Populus tremula × P. tremuloides) are widely planted tree species on former agricultural lands in Northern and Eastern Europe due to their fast growth, high biomass production and CO2 sequestration. As few comparative studies on the biodiversity of silver birch and hybrid aspen plantations have been carried out, we aimed to evaluate above- and below-ground diversity in silver birch plantations (SBs) and hybrid aspen plantations (HAs) and associate the trends with environmental variables. For this, we collected data on herbs, ground-dwelling bryophytes, epiphytic bryophytes, lichens, closed forest species and soil fungi from 10 SBs and 10 HAs (< 25 years of age) in Estonia. The richness and composition of herbs was similar in SBs and HAs, whereas all other groups differed either in species richness, composition or both. Overall, HAs hosted higher richness of ground-dwelling bryophytes and epiphytic lichens and lower richness of epiphytic bryophytes than SBs, which was associated with differences in litter and light conditions. The richness of closed forest species was similar between HAs and SBs and increased in correlation with the area of surrounding forests, whereas the compositions differed. The HAs hosted higher fungal richness of all soil fungi, as well as ectomycorrhizal, saprotrophic and plant pathogenic fungi and differed compositionally from SBs. Based on our findings, both birch and hybrid aspen plantations provide benefits with respect to biodiversity, as they support compositionally different assemblages of bryophytes, lichens, closed forest species and soil fungi.

Herewith, we continue to upgrade the Estonian checklist of lichenized, lichenicolous and allied fungi, and report 14 fungal species new for Estonia, nine of them lichenized (Absconditella pauxilla, Aquacidia trachona, Arthonia helvola, A. reniformis, Lecidea fuliginosa, Lempholemma chalazanum, Lepraria membranacea, Phaeophyscia hirsuta and Trapelia elacista), and four lichenicolous (Bryostigma phaeophyciae, Endococcus verrucosus, Everniicola flexispora and Tetramelas pulverulentus), while Melaspilea bagliettoana is doubtfully lichenized. In addition, four species (Fuscidea cyathoides, Ophioparma ventosa, Rhizocarpon oederi and Sphaerophorus globosus) have been rediscovered, and the presence of one species, Physcia dimidiata, previously known from the literature (Mereschkowski,1913) has been confirmed based on herbarium material. Physcia magnussonii is excluded from the checklist of Estonian lichens.

AbstractAccording 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.

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.

The loss of ancient forests threatens many species. Effective nature conservation needs information on how forest availability in the surrounding landscape in space and time determines the diversity of multiple taxa. We explored the relationship between forest availability at different spatiotemporal scales and the diversity of various groups: vascular plants (woody species, ground layer), epiphytes (bryophytes and lichens), fungi (ectomycorrhizal, arbuscular mycorrhizal, pathogenic, saprotrophic), and carabid beetles. Besides the observed diversity, we also estimated dark diversity, i.e. suitable but absent species. Dark diversity is theoretically a sensitive metric in detecting ecosystem conditions as it is typically relatively large and contains susceptible species. We recorded the observed diversity by field sampling and soil DNA in 100 temperate ancient old-growth forest sites in southern Estonia; dark diversity was estimated for the same sites using species co-occurrence data. Forest availability estimates were obtained from four topographic maps (1900s-2010s) at the 0.5–5 km radius. The biodiversity of forest specialists was higher at larger historical forest availability at the spatial scale of 2–5 km radius. The diversity of light-demanding forest ecotone taxa mainly had negative relationships with young forests on previous agricultural lands (at 0.5–2 km radius). Dark diversity models were often more strongly associated with forest availability than observed diversity models. Dark diversity enhances our understanding of how current and historical forest availability affects local biodiversity. As young forests cannot provide suitable habitats for many forest-dwelling species, stable forest habitats must be preserved as source areas to enhance biodiversity.

Herewith, we continue to upgrade the Estonian checklist of lichenized, lichenicolous and allied fungi, and report thirteen fungal species and one variety as new for Estonia, of them nine are lichenized and five are lichenicolous. Two species – Acarospora oligospora and Lathagrium auriforme – considered to be extinct in Estonia were rediscovered. One species, Usnea articulata, is excluded from the checklist of Estonian lichens.

Lichens are well-known bioindicators and exhibit high sensitivity to environmental changes due to their unique biological characteristics. Despite their ecological significance, lichens are often overlooked in conservation policies both at the European Union (EU) and global levels. The situation is better at the level of national Red Lists that can provide candidate species for regional or global Red Lists, thereby helping to prioritize conservation efforts. To fill a gap at the national level, this article presents the comprehensive data of the Red List of Latvian lichens. For the first time, IUCN threat categories and criteria were applied to assess 85 lichenized and one lichenicolous fungus during 2022-2023. Of these species, 3 were classified as Least Concern (LC), 2 as Data Deficient (DD), 11 as Near Threatened (NT), and 68 were ascribed the threatened categories: 14 to Vulnerable (VU), 27 to Endangered (EN), 27 to Critically Endangered (CR). The majority of Latvian lichens categorized as threatened or near threatened inhabit woodlands, particularly old-growth forests, which face the primary threat of intensive forest management. This article emphasizes the importance of continued evaluation efforts, while also addressing challenges associated with data scarcity and limited lichenological research capacity in Latvia.

Fragmented natural habitats, such as old-growth forests, have been often considered island-like systems. How-ever, whereas the isolation of real islands is mostly a function of their spatial arrangement, the biodiversity of old-growth forest patches is also affected by how well the surrounding suboptimal habitats, such as younger forests, can support the functional connectivity between the old-forest fragments. The latter topic remains largely unclear due to the lack of mechanistic knowledge about the processes behind species' affinity for old forest. Although in animal ecology, functional connectivity has often been investigated with mechanistic agent-based models, these have rarely been applied for passively dispersing organism groups. We used a pattern-oriented modeling approach by combining a spatially explicit agent-based model and an empirical biodiversity dataset of Estonian old-growth nemoral forest sites, to study how forests of different ages between the old-forest frag-ments are exploited by different passively or slowly dispersing functional groups. We found that the establish-ment of ground layer vegetation, epiphytes, ectomycorrhizal and pathogenic fungi is significantly restricted in the younger forests, whereas no clear difference between forest-age classes emerged for survival. Our results thus suggest that establishment, not survival, is the main process behind the species' affinity for old forest, concurring with studies that have demonstrated the importance of suitable microhabitat availability in older forests. We conclude that young secondary forests do not support the connectivity - and consequently, biodiversity - of many old-forest specific groups.

The effect of stand age on biodiversity in the stands of Populus tremula, a keystone tree species in boreal forests, has been insufficiently studied, although this knowledge is crucial for maintaining biodiversity in managed forests. We studied the assemblages of vascular plants, bryophytes and lichens from a chronosequence of aspen stands (n = 20) with an age from 8 to 131 years, aiming to identify the main patterns in species richness and composition. Altogether, 72 vascular plant species were found in the field layer and 17 species in the shrub layer. The total numbers of bryophyte and lichen species were 92 and 104, respectively. Overall, 2 vascular plant, 12 bryophyte and 9 lichen species were the taxa with a high conservation value. Sixteen lichens were regarded as management sensitive or focal species based on earlier studies, and 10 vascular plant species were hemeraphobic (severely disturbed by human activities). The effect of stand age on average species richness estimates depended on the studied species groups. Stand age had a negative effect on the average number of vascular plants, field layer species, apophytic vascular plants and epixylic lichens and a positive effect on the number of lichens, the number of epiphytic bryophytes and lichens and on bryophytes and lichens with a high conservation value. The compositional patterns of vascular plants, bryophytes and lichens strongly correlated with stand age. In addition, stand characteristics, soil properties and light conditions influenced the assemblages, although the direct effects were variable for different groups. The largest differences could be observed in vascular plant, bryophyte and lichen communities between young and old stands; for lichens, also mature and old stands differed significantly. Our results indicate that more than 60 years are required for the recovery of some species groups after clear cutting. At the same time, other species groups were either not negatively affected by clear-cutting or showed a higher richness in younger stands. Therefore, we conclude that the management of aspen stands should involve the combination of different management regimes on the landscape scale (variation from short to long rotations in different stands, maintaining retention trees and ceasing of clear-cutting in some stands). Our results also show that as second-storey Tilia cordata played an important role in maintaining biodiversity in the studied stands, this tree species needs to be preserved in forests where lime trees naturally grow as co-dominants.

The dataset includes vascular plant, bryophyte and lichen species data and environmental data collected from 33 birch stands in Estonia representing three stand types with different restoration approach (birch plantations on previous agricultural land, naturally regenerated stands on previous agricultural land and birch stands on native forest land).

Sixteen species are reported as new for Estonia. Among these species, ten are lichenized and six are lichen-habiting fungi. One lichen-habiting species – Bryostigma molendoi (Heufl. ex Arnold) S.Y. Kondr. & Hur (= Arthonia molendoi (Heufl. ex Arnold) R. Sant.) and one lichenized species – Lecania nylanderiana A. Massal. should be excluded from the Estonian list of lichenized and allied fungi as misidentifications. New locality data are given for two critically endangered (CR) lichens last found more than 45 years ago – Hypogymnia vittata (Ach.) Parrique and Nephroma bellum (Spreng.) Tuck. (Lõhmus et al., 2019). Additional information on the distribution in Estonia is provided for recently described Toniniopsis separabilis (Nyl.) Gerasimova & A. Beck (Gerasimova et al., 2021).

The threat status of 168 lichenized species growing mostly on rocks or ground were assessed in 2022 for the first time in Estonia. The IUCN Red List system (categories and criteria) were used for that purpose. Most of the assessed taxa were microlichens (163), while five macrolichen species were also evaluated. Among the assessed species, 91 were assigned to the threat categories (Critically Endangered – CR, Endangered – EN and Vulnerable – VU), 17 species were assigned to the category Near Threatened (NT), and 41 species were assigned to the category Least Concerned (LC). Category Data Deficient (DD) was assigned for 17 species and the category Regionally Extinct (RE) for two species. Among the threat categories, 35 species were assigned to the category EN, 34 species to VU, and 22 species to CR. In general, most of the evaluated species (81%, 137 species) were growing on different types of rock, 16% (28 species) of species were growing on soil, mosses or plant debris, and three taxa were growing on other substrata. Most of the threatened epigeic and epilithic microlichens were recorded on alvar grasslands growing on ground, limestone pebbles and flatrock or erratic boulders. Er- ratic boulders in various forest types and calcareous cliffs in clint forest were also important habitats for threatened species. Moreover, different rock substrates of anthropogenic origin (walls, buildings and abandoned limestone quarries) performed as significant habitat type for epilithic species. Bush encroachment of open habitats, especially in semi-natural grasslands, serves as the main threat for epigeic and epilithic lichens.

The threat status of 161 lichenized species that were considered common in Estonia was assessed in 2021. For most of these species, it was the second Red List assessment using the IUCN system (the first such evaluation was performed in 2008). The main data sources for species occurrence were the records reported in 100 study sites located throughout the country during 2020, and the PlutoF biodiversity database. 125 species remained, according to the new assessment, in the category Least Concern (LC) and their populations are not under threat in Estonia at present. Two species were placed in the category Not Applicable (NA) because of systematic revisions while 33 species were assigned to the categories Endangered (EN), Vulnerable (VU) or Near Threatened (NT); one further species received the status Data Deficient (DD). Thus, the threat status has changed for 22% of the studied species that had generally been considered common in Estonia. The reasons for this change are variable but there is clear evidence that 26 species have become more threatened during last 12 years.

Mountains provide a timely opportunity to examine the potential effects of climate change on biodiversity. However, nature conservation in mountain areas have mostly focused on the observed part of biodiversity, not revealing the suitable but absent species—dark diversity. Dark diversity allows calculating the community completeness, indicating whether sites should be restored (low completeness) or conserved (high completeness). Functional traits can be added, showing what groups should be focused on. Here we assessed changes in taxonomic and functional observed and dark diversity of epiphytic lichens along elevational transects in Northern Italy spruce forests. Eight transects (900–1900 m) were selected, resulting in 48 plots and 240 trees, in which lichens were sampled using four quadrats per tree (10 × 50 cm). Dark diversity was estimated based on species co-occurrence (Beals index). We considered functional traits related to growth form, photobiont type and reproductive strategy. Linear and Dirichlet regressions were used to examine changes in taxonomic metrics and functional traits along gradient. Our results showed that all taxonomic metrics increased with elevation and functional traits of lichens differed between observed and dark diversity. At low elevations, due to low completeness and harsh conditions, both restoration and conservation activities are needed, focusing on crustose species. Towards high elevations, conservation is more important to prevent species pool losses, focusing on macrolichens, lichens with Trentepohlia and sexual reproduction. Finally, dark diversity and functional traits provide a novel tool to enhance nature conservation, indicating particular threatened groups, creating windows of opportunities to protect species from both local and regional extinctions.

During the last thirty years phylogenetic analyses based on molecular characters have developed from simple single-locus studies into complicated surveys containing multi-locus phylogenies, species trees and possibilities to evaluate the evolutionary history of characters. This has been an exciting era for systematists, including fungal taxonomists. The majority of lichenized taxa have originally been described using morphological characters s. lat. (i.e. traits related to morphology, anatomy and chemistry), and thus the congruence between traditional species description and species delimitation based on their molecular evolutionary history remains a challenge. The use of morphological characters has not been abandoned, as predicted or advocated by some researchers (Lumbsch & Leavitt 2011; Hibbett et al. 2016). However, we now know that the morphology-based approach to species recognition has also been demonstrated in several cases to substantially misrepresent diversity, as it either underestimates the occurrence of cryptic species (Altermann et al. 2014; Boluda et al. 2016) or, on the contrary, overestimates the true diversity due to high levels of intra-specific morphological and chemical variation (Leavitt et al. 2011; Velmala et al. 2014). Therefore, morphological characters continue to be useful for the delimitation of species, but only if their discriminative ability has been verified using phylogenetic analyses. Phenotypic species recognition in the genus Usnea is particularly complicated; the species are delimited by distinctive combinations of diagnostic morphological traits (Clerc 1998, 2011) which may, however, in certain cases be poorly developed or even absent (Clerc 2011). This is aggravated by the fact that there are a great number of Usnea species and high intra-specific variation, leading to a situation where most lichenologists are not able to identify Usnea species or do not undertake the task at all. This drives researchers to find other solutions. An alternative and modern way for the identification of species is DNA barcoding (Schindel & Miller 2005). A test of the success of DNA barcoding with ITS as the barcoding marker in a case study of 112 Usnea specimens from the British Isles (Kelly et al. 2011) was encouraging as the method assigned a high percentage of samples to correct species. Recent thorough analysis (Lücking et al. 2020) found usage of ITS to be a good first approximation to assess species delimitation and recognition in Usnea; however, species boundaries can be reliably established using several markers and different phylogenetic tools. Our main interest in the paper by Mark et al. (2016) focused on phylogenetic issues as we attempted to reconstruct evolutionary relationships in sect. Usnea using DNA data from six markers of 144 specimens, and to determine evolutionarily independent lineages using multiple coalescent-based species delimitation approaches. To perform these tasks, we also followed a traditional approach using morphological characters to identify the samples. Clerc & Naciri (2021) revise the traditional identification of 35 samples used in our analyses (table 1 in Clerc & Naciri (2021)) and present the details of their morphological and chemical characters. Of these, 11 samples appeared to be misidentified in Mark et al. (2016). The main disparity arose from our identification of nine U. dasopoga specimens as U. barbata. Indeed, the distinction between the two species caused difficulties for us, partly because some of the samples used appeared to be atypical or young. It is encouraging to learn that a new, previously unused character, the ratio of medulla/cortex (M/C), has proved to be the most useful discriminant in separating U. barbata and U. dasopoga (fig. 2 in Clerc & Naciri (2021)). Accepting the new morphological identifications, the interpretation of two clades (viz. barbata-chaetophora-dasypoga-diplotypus clade and barbata-intermedia-lapponica-substerilis clade) on our phylogenetic tree (fig. 1b in Mark et al. (2016)) must be reconsidered. The first of the two clades, now the dasopoga clade in Clerc & Naciri (2021), contains only U. dasopoga specimens. However, the clade has low support on the Bayesian and maximum likelihood consensus tree, on account of which the U. dasopoga monophyly is not statistically supported and its sister relationships are unresolved in our analyses. The composition of species in the second, strongly supported clade remains variable, containing samples of U. barbata, U. intermedia, U. perplexans (= U. lapponica) and U. substerilis. The subclades within this clade do not have strong support and morphological species are intermixed between them. We want to point out that the synonymization of U. substerilis under U. perplexans (= U. lapponica) proposed by us was not based merely on the well-supported sister relationship of two samples (SBS15 and LAP5), and thus the reidentification of the latter does not refute the synonymization. This synonymy was also reasonably supported by Lücking et al. (2020). It can be inferred from our phylogenetic tree with new expert identifications based on Author for correspondence: Tiina Randlane. E-mail: tiina.randlane@ut.ee Cite this article: Randlane T and Mark K (2021) Response to Clerc & Naciri (2021) Usnea dasopoga (Ach.) Nyl. and U. barbata (L.) F. H. Wigg. (Ascomycetes, Parmeliaceae) are two different species: a plea for reliable identifications in molecular studies. Lichenologist 53, 231–232. https://doi.org/10.1017/S0024282921000189

Accurate species delimitation has a pivotal role in conservation biology, and it is especially important for threatened species where decisions have political and economic consequences. Finding and applying appropriate character sets and analytical tools to resolve interspecific relationships remains challenging in lichenized fungi. The main aim of our study was to re-assess the species boundaries between Usnea subfloridana and Usnea florida, which have been phylogenetically indistinguishable until now, but are different in reproductive mode and ecological preferences, using fungal-specific simple sequence repeats (SSR), i.e. microsatellite markers. Bayesian clustering analysis, discriminant analysis of principal components (DAPC), minimal spanning network (MSN), and principal component analysis (PCA) failed to separate U. florida and U. subfloridana populations. However, a low significant differentiation between the two taxa was observed across all populations according to AMOVA results. Also, analysis of shared haplotypes and statistical difference in clonal diversity (M) supported the present-day isolation between the apotheciate U. florida and predominantly sorediate U. subfloridana. Our results do not provide a clear support either for the separation of species in this pair or the synonymization of U. florida and U. subfloridana. We suggest that genome-wide data could help resolve the taxonomic question in this species pair.

Less intensive harvesting methods (e.g., selection cutting, shelterwood cuttings) are recommended as alternatives to clearcutting for maintaining mature forest biodiversity in the process of forest regeneration. However, the long-term impact of low-intensity harvesting methods has rarely been studied. Our aim was to clarify the long-term effects of repeated selective cutting, thinning, and shelterwood cutting on the richness, abundance, and species composition of vascular plants, bryophytes, and lichens in Scots pine forests (Pinus sylvestris L.). Data were collected from 25 mature stands located in dry Podzols in southwestern Estonia with a known management history for the last 70 years. Altogether, 35 vascular plant, 41 bryophyte, and 78 lichen species were recorded, including five species with conservational value. Generally, the management history was not related to species richness, except a negative correlation with the species number of epiphytic lichens on conifer trees. In addition, the abundance of two lichen species from the genus Chaenotheca was lower in more frequently managed stands. Species richness and composition were most strongly affected by soil pH and light conditions. We conclude that long-term, low-intensity harvesting of Scots pine forests on nutrient-poor Podzols maintains suitable habitats for vascular plants, bryophytes, and lichens, confirming its suitability for sustainable forest regeneration.