(Sub-)Antarctic endemic cyanobacteria from benthic mats are rare and have restricted geographic distributions

The Antarctic terrestrial macrobiota are highly endemic and biogeographically structured, but whether this also holds true for microbial groups remains poorly understood. We studied the biogeographic patterns of Antarctic cyanobacteria from benthic microbial mats sampled in 84 lakes from two sub-Antarctic islands, as well as from eight Antarctic Conservation Biogeographic Regions (ACBRs) which were previously defined based mainly on macroscopic taxa. Analysis of 16S rRNA gene sequences revealed that Antarctic and sub-Antarctic lakes host significantly different cyanobacterial communities, yet that the bioregionalization pattern did not correspond to the division into ACBRs. Both Antarctic and sub-Antarctic lakes contain a high number of potentially endemic taxa (41% of the total diversity), of which 33.3% attain a relative abundance of < 1%. Our findings highlight the uniqueness of Antarctic microbiota and the need for increased protection of inland waters in both Antarctica and the sub-Antarctic islands.