Comparative Analysis of the Mycobiomes of Two Terrestrial Isopods, Armadillidium vulgare and Spherillo obscurus.

Terrestrial isopods serve as key decomposers in soil ecosystems and harbor diverse microbial communities that may contribute to their ecological functions. However, specific mycobiome composition of terrestrial isopods remains unknown. Therefore, in this study, we investigated and compared the fungal communities associated with the two terrestrial isopods, Armadillidium vulgare and Spherillo obscurus, which co-occur in island habitats in South Korea. Through metabarcoding based on the internal transcribed spacer region, we characterized fungal communities using 16 individuals collected from the Heuksan and Eocheong Islands. In total, 252 operational taxonomic units were identified, of which 27 were shared between the two hosts. Comparatively, S. obscurus harbored a significantly more diverse and phylogenetically rich fungal community, including taxa from Ascomycota, Basidiomycota, and Mortierellomycota, whereas A. vulgare was largely dominated by Mycosphaerella (Dothideomycetes, Ascomycota). Alpha and beta diversity analyses revealed the host-associated enrichment, rather than the geographic location, as the primary factor influencing the mycobiome composition. Linear discriminant analysis further revealed host specialists, with distinct fungal taxa showing preferential associations with each isopod species. Our findings suggest that host identity strongly influences the fungal community assembly in isopods and that S. obscurus supports diverse ecological niches for fungal colonization. Overall, this study provides novel insights into host-fungus interactions and expands the current understanding of symbiotic mycobiomes in soil macroinvertebrates.