## 3 Results and Discussion
### Metabarcoding vs. Culture-Dependent Diversity and Biodeterioration-Related Organisms  
Regarding the metabarcoding fungal diversity obtained in the present study, our results show a strong dominance of the class _Dohtideomycetes_ in all samples, regardless of the biodeterioration pattern observed. Other classes such as _Sordariomycetes_, _Eurotionycetes_ and _Agaricomycetes_ were also consistently present across all samples but in much lower abundance, with all classes belonging to _Ascomycota_. These results are consistent with the literature, with _Dohtideomycetes_ being one of the most frequent groups isolated from rocks [93; 94; 95; 96; 97; 98; 99; 100; 101]. _Dohtideomycetes_ are very diverse in term of species, encompassing morphologically and ecologically diverse fungi with different lifestyles and modes of nutrition. While many species are associated with plants (either as pathogens or as epiphytes), saprobic, coprophilous, lichen-forming and rock-inhibiting fungi are also present in this class [102]. The most common recovered fungal sequences in _Dohtideomycetes_ were composed of the orders _Capnodiales_, holding genera such as _Caldosporium_, _Toxicocladosporium_, and _Needeviesia_, and _Pleosporales_, including the _Didymellaceae_ family and _Alternaria_; however, abundance of these differed between samples. Along with the _Eurotionycetes_ genera frequently detected, such as _Aspergillus_, _Penicillium_, _Taleromyces_ and _Cyphellophora_, most of these are generally widely distributed, highly ubiquitous and are considered among the most common genera found as indoor extremotolerant contaminants [102; 103; 104; 73; 76; 77; 105; 106; 107; 108; 109; 110; 111; 112; 113; 114; 115; 116; 117; 118; 119; 120; 121; 122; 123; 124; 125; 126; 127; 128; 129; 130; 131;  
Corticum, Xylodon_ and _Coprinellus_ (_Agaricomycetes_) are saprotroph fungi belonging to _Basidiumycota_[112, 113, 114]. The first two genera are found mainly associated with green biofilms, while _Coprinellus_ was present in all four locations, especially in black discoloration (L3), possibly indicating a more xerophilic and halotolerant profile. Moreover, _Candidia_ (_Ascomycota, Saccharomyces_), _Malassezia_ (_Basidiumycota, Malasseziales_) and _Saitozyma_ (_Basidiumycota, Trentellomycetes_) are yeast-like fungi, being the first two opportunistic parasites in human and other warm-blooded animals [115, 116], whereas _Saitozyma_ is commonly found in soil and plants [117, 118]. In a study conducted in the Morassina cave [119], where the yeast genus _Candidia_ has been identified, reference was made to its ability to grow under acidic conditions. Finally, a greater number of distinctive specific taxa associated with the different types of biodeterioration observed were mainly present in the fractions with lower abundances. While green biofilms had a very rich and diverse populations composition, a black discoloration outline (L3) was highly dominated by _Capnodiales_ (-70%), particularly _Neodevriesiacea_ (-40%), _Cladosporiaceae_ and unclassified _Capnodiales_, demonstrating the high prevalence of black fungi. The salt efflorescence was the most unique scenario, characterized by the presence of distinct phyla such as _Mortierellomycota_, _Glomeromycota_ and _Cityridiomycota_. Unclassified _Capnodiales_ (-30%) was also markedly present in this sampling point. When considering the HTS data, highly abundant taxa did not always belong to well-known taxonomic groups, but additionally to unidentified lineages. Therefore, we can hypothesize that species richness within those, particularly _Dothideomycetes_, _Eurotomycetes_ and _Sordariomycetes_, remains woefully underestimated, and that many taxa previously unknown are present within, highlighting the need for further studies, especially for fungi colonizing rocky substrates. In addition, generalized studies of community diversity by molecular methods alone lack the discrimination between living and dead material, or active and dormant organisms.