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The boundaries of the family Catillariaceae have largely remained untested through phylogenetic methods. Recent studies have led to the transfer of several genera previously classified in Catillariaceae to the newly described family Leprocaulaceae. Despite these changes, the distinction between Catillariaceae, Leprocaulaceae, and Catinariaceae remains ambiguous. To address these uncertainties, we conducted a comprehensive phylogenetic analysis with improved taxon sampling (including the type species of all genera) and a six-marker dataset, including two newly developed markers. Our results strongly support Catillariaceae as a monophyletic group including the currently accepted genera Catillaria, Catinaria, Halecania, Leprocaulon, Solenopsora, and Speerschneidera. Consequently, we synonymize Catinariaceae and Leprocaulaceae with Catillariaceae, resulting in a revised, morphologically cohesive circumscription. The redefined Catillariaceae includes all Lecanoromycete species characterised by a Catillaria-type ascus, paraphyses with thickened brown pigmented caps, and 2-celled, unpigmented ascospores (in sexually reproducing species). However, our findings question traditional generic circumscriptions in this group, revealing paraphyly in Catillaria, Halecania, Leprocaulon, and Solenopsora. As a step towards resolving these issues, we describe the new genera Caelochroma (for Catillaria atomarioides) and Halecaniella (for Halecania viridescens), and resurrect the genera Microlecia (for Catillaria lenticularis) and Placolecania (for part of Solenopsora not including its type). Several taxonomic challenges persist however, particularly within Leprocaulon and Solenopsora s.l. Additionally, we demonstrate that the genus Placolecis does not belong in Catillariaceae. We describe Halecania abscondita, a new corticolous species from northern Sweden, propose the new combination Catillaria nubila (for C. chalybeia var. chloropoliza) and designate a lectotype for Lecania alpivaga.

This study investigates species boundaries in the lichen genus Arctomia (Arctomiaceae, Ascomycota) using an integrative approach combining molecular phylogenetics, full Bayesian population delimitation, heuristic and model-based species delimitation, and supervised machine learning applied to morphological data. We analysed DNA sequence data from four markers: the internal transcribed spacer (ITS) region and the large subunit (nrLSU) of the ribosomal RNA gene, the DNA-directed RNA polymerase II subunit RPB1 (RPB1), and the small subunit of the mitochondrial ribosomal RNA (mrSSU) gene. Additionally, we assessed morphological measurements of ascospores and apothecia. Phylogenetic analyses consistently recovered Arctomia, also including A. interfixa, as monophyletic. The traditional classification of A. delicatula was found to encompass multiple species. We recognise three distinct species within this complex: A. delicatula s.str., A. acutior (resurrected from synonymy with A. delicatula), and a newly described species, A. confusa. Supervised machine learning, trained on morphological data from sequenced specimens, successfully learnt morphological differences between species in the training set and subsequently classified unseen (unsequenced) specimens, including type material, with high probabilities. Arctomia acutior can be distinguished from A. delicatula and A. confusa by its narrower ascospores, smaller apothecia, and preference for bark substrates. While A. confusa is similar to A. delicatula, it can be separated by slightly narrower ascospores. Arctomia acutior inhabits decaying bark, A. delicatula s.str. overgrows soil and bryophytes on soil, whereas A. confusa can be found in either of the habitats. Our study demonstrates that the novel application of machine learning trained on morphological measurements from sequenced specimens offers a promising tool for distinguishing between species when morphological differences are subtle and for classifying historical specimens (including types) based on morphology when DNA sequences are not available.

This paper contains an identification key in Swedish and English to the species of Bacidina currently known from Sweden, Norway, Denmark, and Finland . The keys are largely taken from Ekman (2023), with adaptations and corrections.

This paper contains an identification key in Swedish to the species of Nephroma currently known from Sweden, Norway, Denmark, Finland, and Iceland.

This paper contains an identification key in Swedish to the species of Bacidia currently known from Sweden, Norway, Denmark, Finland, and Iceland.

Question: What are the extent and the possible causes of imperfect detection in lichens? Because lichens are sessile and lack seasonality, they should be easier to survey than animals that can move or plants and fungi with seasonal morphology, and one could therefore expect relatively high detection probabilities.

Location: 826 standardised sampling plots across Switzerland.

Methods: Using repeated detection/non-detection data from a national lichen survey conducted by professional lichenologists, we estimated the mean and variation in detectability for 373 tree-living species with a multi-species occupancy model. We also quantified the effect of species conspicuousness, identifiability and observer experience on detection probability.

Results: The average detection probability for a single survey was unexpectedly low with an average of 0.49 (range across species: 0.25-0.74). Conspicuous species showed higher average detectability (0.56) than inconspicuous species (0.41), and identifiability as well as previous experience with a species substantially increased the probability of a person detecting it. Accounting for experience, the mean detection probabilities of observers ranged from 0.32 to 0.69.

Conclusions: Our study confirms that detection probability per survey is often far below 1 also in sessile organisms, even when a standardised survey is conducted by experts. When species are seasonal (plants, fungi, etc.), survey areas are larger, or field personnel are less experienced, as is the case for many surveys and monitoring programs, detectabilities are likely to be substantially lower. We therefore argue that imperfect detection should systematically be considered in the survey design and data analysis also for sessile organisms.

The species described as Bacidia genuensis is transferred here to Bacidina as B. genuensis (Ramalinaceae, Lecanorales, lichenized Ascomycota). An updated morphological description is provided. The species is characterized by mostly blackish apothecia on a thick, microsquamulose thallus, a crystal-inspersed proper exciple that is mostly prosoplechtenchymatous, an ascus with a wide and dome-shaped axial body and an expanded c-layer (resulting in a thin, amyloid d-layer), a blue-green pigment in the epihymenium, proper exciple, and pycnidial wall, and an orange-brown, K+ intensifying pigment in the hypothecium and sometimes proper exciple. This combination of characters sets the species apart from its potentially close relatives Bacidina egenula and B. indigens, as well as the superficially similar, but more distantly related, Toniniopsis bagliettoana. Bacidina genuensis is currently known from a few sites in northern Italy, where it inhabits weathered and apparently shaded mortar of masonry.

Four species of Bacidina (Ramalinaceae, Lecanorales, Ascomycota) are described as new to science from northern Europe (mainly Swedish material): Bacidina ferax S.Ekman, Bacidina lignicola S.Ekman, Bacidina maculans S.Ekman and Bacidina populnea S.Ekman. Another two species are resurrected from synonymy: Bacidina caerulea (Körb.) S.Ekman (based on Bacidia caerulea Körb.) and Bacidina circumpallens (Nyl.) S.Ekman (based on Lecidea circumpallens Nyl.). An additional four combinations are made: Bacidina friesiana (Hepp) S.Ekman (based on Biatora friesiana Hepp), Bacidina subfuscula (Nyl.) S.Ekman (based on Lecidea subfuscula Nyl.), Bacidina tarandina (Nyl.) S.Ekman (based on Lecidea tarandina Nyl.) and Bacidina tenella (Kullh.) S.Ekman (based on Bacidia tenella Kullh.). The morphology, distribution and nomenclature of all 28 species of Bacidina currently known from Scandinavia (Sweden, Norway, Denmark) are treated and an identification key is provided. In addition, Bacidina friesiana is discussed (for comparison with B. caerulea) even if it is not currently known from Scandinavia. Two of the treated species (B. epithallina ined., B. parasitica ined.) are parasites on cyanolichens but are not formally introduced here because of the scarcity of available material. Bilimbia arceutinoides Anzi is reduced to synonymy with Bilimbia sabuletorum (Schreb.) Arnold and Lecidea luteola var. chlorotica Ach. is reduced to synonymy with Bacidia rubella (Hoffm.) A.Massal. It is concluded that despite the present work, the diversity of the genus Bacidina remains insufficiently understood, at least in Scandinavia.

The new combination Thalloidima squamatum is proposed for a morphologically and phylogenetically distinct species, until now included within the variation of T. sedifolium. Compared to T. sedifolium, the species is characterized by its larger squamules and apothecia, shorter ascospores, the pale color of the excipulum, and its habitat growing on moss cushions over calcareous rock or directly on rock rather than on soil. Most of the material studied originates from Norway and Sweden, but specimens are also reported from Austria, Croatia, Germany, Greenland, Italy, Poland, Russia, Scotland and Switzerland.