Opportunistic fungi found in fairy rings are present on different moss species in the Antarctic Peninsula

We surveyed the distribution and diversity of fungi present in moss fairy rings from the South Shetland Islands. In the different islands accessed, the mosses Bartramia patens, Brachythecium austrosalebrosum, Bryum pseudotriquetrum, Pohlia nutans, Polytrichastrum alpinum, Sanionia uncinata, Syntrichia magellanica, and Syntrichia saxicola were infected with fairy rings. Among them, B. patens, B. pseudotriquetrum, P. nutans, P. alpinum, S. magellanica, and S. saxicola were reported for the first time as species susceptible to infection with fairy rings. From five different fairy ring moss species sampled, we isolated 40 fungal taxa identified as belonging to the genera Alpinaria, Cadophora, Cladosporium, Chalara, Cosmospora, Drechmera, Glarea, Gyoerffyella, Hymenoscyphus, Juncaceicola, Melanodiplodia, Mortierella, Mycosysmbioses, Pseudogymnoascus, Phoma, and Velucrispora. A high level of fungal richness was associated with the infected mosses, and Mortierella was the dominant genus. However, most of the fungi were present as minor components of the fungal assemblages. Among the mosses studied, S. uncinata harboured the greatest fungal diversity. Some fungal taxa present have previously been reported as opportunistic plant pathogens, including Cladosporium sp. and Phoma herbarum. We hypothesize that some of the fungi recovered from fairy ring mosses might represent secondary opportunistic pathogens and contribute to the reduced natural defences of the infected mosses, thus accelerating the dissemination of the pathogenic fairy rings in the Antarctic Peninsula. In addition, the presence of fairy rings on previously unreported moss species suggests that the disease may be becoming more widespread in Antarctica.