Cryptic associated fungi and algae isolated from Antarctic epilithic lichens of the Victoria Land and the description of five new fungal species

Lichen thalli are niches for microorganisms, including microfungi, microalgae and non-photosynthetic bacteria, which form communities of variable composition, often shaped by the environmental conditions under which the lichen thalli develop. In Antarctica lichens represent an important group of organisms characterized by a high percentage of endemism, which have specialized to grow on rocks, as the predominant substrate for colonization. Here, Antarctic epilithic thalli of five endemic and three cosmopolitan lichen species have been investigated for their potential role as fungal species hotspots. The culturable fraction of the Antarctic lichen-associated fungi and algae was uncovered with the aim to isolate as many species as possible and find whether taxa are strictly connected to the Antarctic environment or are cosmopolitan species that particularly associate to lichens in harsh, extreme environments. Over 300 fungal and algal inocula grew in culture, among which we recognized species previously described, as well as five new fungal species in Ascomycota and Basidiomycota, namely: Petrophila complexa sp. nov., Dactylospora endolichenica sp. nov., Knufia elegans sp. nov., Pseudeurotium lichenicum sp. nov., and Kurtzmanomyces lichenum sp. nov. These species seem to select lichens as their preferred niche, both in Antarctica and worldwide. Indeed, the major representatives of the lichen mycobiota are fungi that do not show any specificity toward a particular lichen host species, rather toward the lichen thallus in general, as a structure in which spores, yeast cells and mycelia fragments thrive or rest. Particularly in Antarctica, where conditions on rock surfaces are far more selective than elsewhere, lichen thalli would be even more exploited as suitable niches by other fungi for their evolution and diversification.