## 3 Results and Discussion
### High-Throughput Sequencing Data Analysis  
Fungal community composition analysis was assessed by sequencing ITS regions of the 18 S rRNA gene using the Illumina MiSeq(r) v3 platform. A total of 333,803 quality reads were recovered from all the samples and, at a 97% similarity cutoff level, grouped into 1588 operational taxonomic units (OTUs) at species level. The Good's Coverage index of all samples was over 99%, which indicated an adequate level of database coverage to identify most of the diversity in the samples. There were 612, 662, 833 and 270 OTUs identified in L1, L2, L3 and L4, respectively, and out of the total of observed OTUs, only 38 were shared among all four samples, which accounted for 2.4% of the total OTUs (Figure 3). These results point toward the presence of a higher number of distinctive populations associated with distinct biodeterioration patterns. Figure 3: Venn diagram analysis of shared OTUs between samples. The Chao 1, Abundance-based Coverage (ACE), Shannon (H), Gini-Simpson (1-D) and Dominance (D) indices were determined to quantify the Alpha diversity and understand the structure of the fungal community with respect to its richness (reflect the number of OTUs in samples) and evenness (reflect the distribution of abundances within OTUs). The greater the Chao or ACE index, the higher the expected species richness; the greater the H or 1-D indexes, the higher the diversity and the smaller the D, the higher the diversity. Analysis of Alpha diversity indices demonstrated a high fungal diversity in all four samples, with sample L1 presenting the greatest richness and diversity values and sample L3 the least, despite being the sample with the highest OTU count. Sample L1 also presented the lowest D value, indicating an even taxa distribution within this sampling point, in contrast with sample L3 exhibiting the highest D value suggesting the presence of a more prevalent taxon (or taxa). The detailed statistical data of \(\alpha\)-diversity indexes are shown in Table 1.  
The OTUs were assigned to 7 phyla, 251 families and 500 genera, while only <1% of sequences were not assigned to any known phylum. At the phylum level, _Ascomycota_ (accounting for 76.32% to 94.81%) and _Basidiumycota_ (3.84% to 20.52%) were the two major fungal taxa across all samples. _Mortierellomycota_ was the third most abundant phylum (>5% in L4) but, together with the phyla _Chytridiomycota_ and _Glomeromycota_, was only detected in samples L1 and L4. _Rozellomycota_ was present only in the L1 and L2 samples. The relative abundance of these last three phyla along with _Mucoromycota_ was lower than 3% and differed across the samples. Figure 3 exhibits the relative abundance at the phylum level (Figure 4a), family level (Figure 4b) and genus level (Figure 4c). For the higher classification levels, only the 20 most abundant family and genera, considered individually for each sample, were discriminated in the graphs. Less abundant taxa were pooled and indicated as \"Other\". The predominant families were _Cladosporiaceae_ (25.9%), _Aspergillaceae_ (7.5%), _Capnodiales_, unclassified (6.7%), _Saccharomyces_fam Incertae sedis_ (4.8%) and _Didymellaceae_ (4.8%) in sample L1; _Cladosporiaceae_ (26.3%), _Needevriesiaceae_ (18.3%), _Sordariumycetes_unclassified_ (10.3%), _Cymbellophoraceae_ (8.3%) and _Hyporeales_fam Incertae sedis_ (5.6%) in sample L2; _Needevriesiaceae_ (40.5%), _Capnodiales_, unclassified (17.4%), _Cladosporiaceae_ (8.4%), _Cordypitaceae_ (5.7%) and _Aspergillaceae_ (5.3%) in sample L3; and _Capnodiales_, unclassified (34.5%), _Cordypitaceae_ (5.7%), _Nectriaceae_ (5.6%), _Mortierellaceae_ (5.3%) and _Eurotiomycetes_unclassified 4.4%) in sample L4. The composition of the fungal community was further analyzed at the genus level. A total of 500 fungal genera were identified via taxonomic summary: 285 in sample L1; 251 in sample L2; 269 in sample L3; and 150 in sample L4. Of these 500 only 43 were common to all four spots, with samples L2 and L3 having the largest number of shared genera.