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As self-supporting and long-living symbiotic structures, lichens provide a habitat for many other organisms beside the traditionally considered lichen symbionts-the myco- and the photobionts. The lichen-inhabiting fungi either develop diagnostic phenotypes or occur asymptomatically. Because the degree of specificity towards the lichen host is poorly known, we studied the diversity of these fungi among neighbouring lichens on rocks in an alpine habitat. Using a sequencing metabarcoding approach, we show that lichen mycobiomes clearly reflect the overlap of multiple ecological sets of taxa, which differ in their trophic association with lichen thalli. The lack of specificity to the lichen mycobiome is further supported by the lack of community structure observed using clustering and ordination methods. The communities encountered across samples largely result from the subsampling of a shared species pool, in which we identify three major ecological components: (i) a generalist environmental pool, (ii) a lichenicolous/endolichenic pool and (iii) a pool of transient species. These taxa majorly belong to the fungal classes Dothideomycetes, Eurotiomycetes and Tremellomycetes with close relatives in adjacent ecological niches. We found no significant evidence that the phenotypically recognized lichenicolous fungi influence the occurrence of the other asymptomatic fungi in the host thalli. We claim that lichens work as suboptimal habitats or as a complex spore and mycelium bank, which modulate and allow the regeneration of local fungal communities. By performing an approach that minimizes ambiguities in the taxonomic assignments of fungi, we present how lichen mycobiomes are also suitable targets for improving bioinformatic analyses of fungal metabarcoding.

Arthonia parietinaria is described as new to science. Host of the type and at the same time the only confirmed host species is the foliose macrolichen Xanthoria parietina. Sequence data of nucLSU rRNA genes reveal a close relationship to Arthonia molendoi. A. parietinaria is recorded for many countries in Europe, western Asia, and northern Africa.

Lichens are frequently colonized by specialized, lichenicolous fungi. Symptomatic lichenicolous fungi usually display typical phenotypes and reproductive structures on the lichen hosts. The classification based on these structures revealed different host specificity patterns. Other fungi occur asymptomatically in the lichen thalli and are much less known. We aimed at studying the diversity of lichen-associated fungi in specific, lichen-rich communities on rocks in the Alps. We tested whether lichenicolous fungi developing symptomatically on their known hosts also occur asymptomatically in other thalli of the same or of different host species. We collected lichen thalli according to a uniform sampling design comprising individuals adjacent to thalli that showed symptoms of lichenicolous fungal infections. The total fungal communities in the selected lichen thalli were further studied by single-strand conformation polymorphism (SSCP) fingerprinting analyses and sequencing of internal transcribed spacer (ITS) fragments. The systematic, stratified sampling strategy helped to recover 17 previously undocumented lichenicolous fungi and almost exhaustively the species diversity of symptomatic lichenicolous fungi in the studied region. The results from SSCP and the sequencing analyses did not reveal asymptomatic occurrence of normally symptomatic lichenicolous fungi in thalli of both the same and different lichen host species. The fungal diversity did not correlate with the species diversity of the symptomatic lichenicolous fungus-lichen host associations. The complex fingerprint patterns recovered here for fungal communities, in associations of well-delimited lichen thalli, suggest lichen symbiosis as suitable subjects for fungal metacommunity studies.