Phylogenetic analyses using mtSSU and nuITS sequences of Buellia violaceofusca (previously placed in Lecanoromycetes), a sterile, sorediate lichen having a trebouxioid photobiont, surprisingly prove that the species is conspecific with Lecanographa amylacea (Arthoniomycetes), a fertile, esorediate species with a trentepohlioid photobiont. These results suggest that L. amylacea and B. violaceofusca are photomorphs of the same mycobiont species, which, depending on the photobiont type, changes the morphology and the reproduction strategy. This is the first example of a lichenized fungus that can select between Trebouxia (Trebouxiophyceae) and trentepohlioid (Ulvophyceae) photobionts. Trebouxia photobionts from the sorediate morphotype belong to at least three different phylogenetic clades, and the results suggest that Lecanographa amylacea can capture the photobiont of other lichens such as Chrysothrix candelaris to form the sorediate morphotype. Phylogenetic analyses based on rbcL DNA data suggest that the trentepohlioid photobiont of L. amylacea is closely related to Trentepohlia isolated from fruticose lichens. The flexibility in the photobiont choice enables L. amylacea to use a larger range of tree hosts. This strategy helps the lichen to withstand changes of environmental conditions, to widen its distribution range and to increase its population size, which is particularly important for the survival of this rare species.

Lecanora stainislai is characterized by a very thin sorediate thallus, forming a more or less continuous layer of soredia and by the production of usnic acid and zeorin. It usually grows on smooth bark of trees in forests and is known from the Czech Republic, Norway, Poland, Russia, Ukraine and western North America (Canada, USA). It is chemically similar to the sorediate L. compallens, which however has an episubstratal thallus in non-sorediate parts and often delimited soralia. They have also different phylogenetic positions within the L. symmicta group. Moreover, based on molecular marker analysis the position of L. expallens is resolved within this group for the first time.

Six new Micarea species are described from Europe. Phylogenetic analyses, based on three loci, i.e. mtSSU rDNA, Mcm7 and ITS rDNA and ancestral state reconstructions, were used to evaluate infra-group divisions and the role of secondary metabolites and selected morphological characters on the taxonomy in the M.prasina group. Two main lineages were found within the group. The Micareamicrococca clade consists of twelve species, including the long-known M.micrococca and the newly described M.microsorediata, M.nigra and M.pauli. Within this clade, most species produce methoxymicareic acid, with the exceptions of M.levicula and M.viridileprosa producing gyrophoric acid. The M.prasina clade includes the newly described M.azorica closely related to M.prasina s.str., M.aeruginoprasina sp. nov. and M.isidioprasina sp. nov. The species within this clade are characterised by the production of micareic acid, with the exception of M.herbarum which lacks any detectable substances and M.subviridescens that produces prasinic acid. Based on our reconstructions, it was concluded that the ancestor of the M.prasina group probably had a thallus consisting of goniocysts, which were lost several times during evolution, while isidia and soredia evolved independently at multiple times. Our research supported the view that the ancestor of M.prasina group did not produce any secondary substances, but they were gained independently in different lineages, such as methoxymicareic acid which is restricted to M.micrococca and allied species or micareic acid present in the M.prasina clade.

The landscape-scale extinction of a tree species may have a negative impact on diversity of associated epiphytic species. We used ordination and hierarchical clustering methods to assess landscape and the community level effects of reduction in the abundance of European ash Fraxinus excelsior, caused by ash dieback, on the associated epiphytic lichen biota in Białowieża Forest (Poland)—the best preserved forest complex in Central Europe. At the landscape level ash decline impact on the biota of ash-associated epiphytic lichens was weak, due to the high diversity of tree species, which may serve as potential alternative hosts. At this level, oak and hornbeam are the most important alternative hosts, assuring the maintenance of ash-associated epiphytic lichens. Lime, alder, and hazel appeared to be less important but still may serve as substitute phorophytes to approximately 2/3 of the ash-associated lichen biota. About 90% of epiphytic biota are likely to survive on the landscape scale. However, at the community level of alder-ash floodplain forest, where ash was dominant, about 50% of ash-associated epiphytic lichen species are threatened by ash dieback. Our results highlight the importance of a spatial scale in conservation biology. Protection of large forest areas with rich diversity of phorophyte trees increases chances of survival of the associated epiphytic organisms.

Micarea soraliferasp. nov., a new sorediate species belonging to theM. prasinagroup, is characterized by soralia developing directly from the endoxylic thallus or small external areoles, as well as the presence of micareic acid. Phylogenetic analyses of mtSSU rDNA sequences have shown that its closest relative isM. subviridescens. ITS rDNA sequence, a marker proposed as the universal barcoding region of fungi, was generated from the holotype.