Are recently deglaciated areas at both poles colonisedby the same bacteria?

Polar glacier forefields offer an unprecedented framework for studying community assembly processes in regions that aregeographically and climatically isolated. Through amplicon sequence variant (ASV) inference, we compared thecomposition and structure of soil bacterial communities from glacier forefields in Iceland and Antarctica to assess overlapbetween communities and the impact of established cryptogamic covers on the uniqueness of their taxa. These pioneermicrobial communities were found to share only 8% of ASVs and each taxonomic group’s contribution to the shared ASVdata subset was heterogeneous and independent of their relative abundance. Although the presence of ASVs specific to oneglacier forefield and/or different cryptogam cover values confirms the existence of habitat specialist bacteria, our data showthat the influence of cryptogams on the edaphic bacterial community structure also varied also depending on thetaxonomic group. Hence, the establishment of distinct cryptogamic covers is probably not the only factor driving theuniqueness of bacterial communities at both poles. The structure of bacterial communities colonising deglaciated areasseems also conditioned by lineage-specific limitations in their dispersal capacity and/or their establishment andpersistence in these isolated and hostile regions.