Are glacier surfaces the last refuge of an evolutionary ancient lineage of unknown fungi?

Glaciers and ice-sheets are increasingly recognized as the homes of surprisingly diverse and active microbial ecosystems. Even the mere prospect of life in Antarctic subglacial lakes, isolated for many millennia, attracts major international attention and investment. However since life certainly flourishes in unusual habitats on glacier surfaces. these should not be overlooked in our attempts to explore microbial biodiversity. Cryoconite holes are one such habitat, formed when rocky dusts are colonized by a diverse and highly active microbial consortium, forming a darkened microbe-mineral aggregate which increases the transfer of the sun's energy to ice and thus accelerates surface melt. My doctoral studies centred on the diversity and functioning of the bacterial community of cryoconite, which is dominated by organisms closely related to taxa in a broad range of habitats world-wide. In stark contrast, of the eukaryotes inhabiting cryoconite on High Arctic glaciers, the most abundant group by biomass, Fungi, appears strongly dominated by two related groups of fungi hitherto unknown to science. These fungi account for 75% of the sequences in collections of fungal DNA extracted from Svalbard cryoconite, and according to microscopy using genetic stains specific to the group, are derived from small ovoid cells attached to debris. Sequenced genes from specific DNA tests for the fungi demonstrate their presence in cryoconite worldwide suggesting a broad geographic range while the absence of affiliated sequences from DNA databases and the failure to detect the group in periglacial habitats imply their restriction to the cryoconite group near the root of the fungal tree of life and provide a crudely estimated divergence during the Neoproterozoic era, which consisted of major world-wide glaciations, including a hypothesized Snowball Earth. Little else is known about these fungi, tentatively named the cryomycetes. Therefore, I seek support to detail their evolutionary history, population structure, ecological functions and interactions. Doing so will permit the testing of the hypotheses that i)cryomycetes assume a significant role in the functioning of the extant cryoconite ecosystem ii)they form a major new branch on the fungal tree of life iii)cryoconite holes have formed a stable refuge for these fungi over glacial cycles. As a consequence, I anticipate insights into the interactions between cryoconite biodiversity and melting glaciers, both in the present day, and potentially in the postulated transition from a Neoproterozoic Snowball to a Mudball Earth.