The Antarctic lichens as evolutionary niches for microbial diversification

This thesis presents a comprehensive analysis of the microbial communities inhabiting epilithic lichen thalli in the Antarctic region of Victoria Land. Focusing on five endemic and three cosmopolitan lichen species, the research aims to bridge the gap in understanding the diversity of the myco- and micro-biome in these extreme environments. Using an integrated methodology that combines culture-dependent techniques and metabarcoding of fungal DNA, the study characterizes both the bacterial and fungal communities within the lichens' thalli. The metabarcoding analysis revealed a mycobiota predominantly composed of Ascomycota (specifically Chaetothyriomycetes and Dothideomycetes) and Basidiomycete yeasts, alongside a microbiota of Pseudomonadota, Cyanobacteria, and Bacteroidota. Notably, the composition of these communities varies based on the species of the lichenizing fungus and to a lesser extent on their distribution as endemic or cosmopolitan. The culture-dependent approach led to the isolation of 328 fungal strains, primarily from Ascomycota. This study also identified four new species of fungi and anticipates the description of new species of Basidiomycetes yeast and Trebouxia photobiont. These findings underscore the importance of lichens as hotspots for microbial diversity and evolution in the selective conditions of Antarctica. The study concludes that lichens play a critical role in conserving microbial biodiversity in Antarctic ecosystems, emphasizing their significance as niches for microbial diversification and evolutionary studies.