Cold terrestrial habitats, defined by average temperatures below 5 °C, include over 80% of the Earth’s terrestrial surface. These environments encompass polar regions (Arctic and Antarctica), high-altitude mountains across Asia, Europe, and the Americas, cold deserts, and deep-sea ecosystems. Despite the extreme abiotic stressors (e.g., low temperatures, limited water availability, high solar irradiations, etc.), these ecosystems harbor psychrophilic and psychrotolerant fungal communities, including both yeast and filamentous life forms. These organisms have evolved a range of adaptive strategies to maintain their metabolic functionality at low temperatures, namely reduced growth kinetics, production of cold-active enzymes, and accumulation of cryoprotective compounds (e.g., heat shock proteins, polyols, etc.). Furthermore, in response to reduced membrane fluidity caused by low temperatures, psychrophilic and psychrotolerant fungi typically enhance membrane fluidity by increasing the proportion of unsaturated fatty acids within their lipid bilayers.

Climate change is exerting an increasing pronounced impact on cold terrestrial ecosystems, with evident effects, such as extended ice-free periods in Arctic and alpine regions. Consequently, the investigation on the diversity of fungal communities in polar and high-altitude cold ecosystems is of strategic relevance for improving our understanding of fungal ecology in these underexplored biomes.

To characterize the taxonomic structure and ecological dynamics of these fungal communities, DNA metabarcoding approaches (involving next-generation sequencing of the ITS region followed by bioinformatics analyses) were applied to environmental samples, such as soil (including permafrost), brine, ice, and both epi- and hypo-glacial debris. Taxonomic assignment of operational taxonomic units (OTUs) revealed that Ascomycota dominated among filamentous forms, whereas Basidiomycota were more abundant among yeast taxa. Alpha- and beta-diversity analyses demonstrated high phylogenetic variability even at local spatial scales. Environmental parameters such as salinity, electrical conductivity, pH, and organic C were identified as significant (p < 0.05) selective factors driving the relative abundance of specific fungal taxa.