Biogeography and uniqueness of filamentous terrestrial fungi in the polar regions

Fungi are widely distributed on our planet, including in extremely harsh habitats, such as the polar regions. The extreme conditions of those habitats limit the number of organisms capable of living there, but some fungi are adapted to the polar conditions and play essential roles in nutrient cycling. However, knowledge about their diversity, distribution, and functioning is fragmented, and approaches used to study them are diverse, often yielding difficult-to-compare results. We present maps with locations of mycological studies in the Arctic and Antarctica, as well as a list of mycelial fungi found on various terrestrial substrates through cultivation on nutrient media and/or molecular methods. These fungi were identified to the species level based on morphological-cultural features or gene-sequence analysis. Analysis of the methods applied to study fungi in different substrates shows that a combination of multiple methods is optimal to study species composition. The taxonomic affiliation of the identified species to different fungal divisions is largely determined by habitat conditions and research methods. The largest number of species belongs to the divisions Ascomycota and Basidiomycota. The predominant ecological groups were saprotrophic and symbiotic fungi. The majority of 1324 discovered fungal species are known as cosmopolitan species. Approximately one-fifth of the fungi were identical between the Arctic and Antarctica, only a few species are known to be endemic to Antarctica or Arctic, and there are 1–6 identified bipolar species. Claims of endemism of polar-region fungi are relatively weakly supported.