The genus Stauroneis (Bacillariophyceae) in the Antarctic region

Aim To provide a detailed biogeography of the diatom genus Stauroneis in the Antarctic and sub‐Antarctic regions and to establish the biogeographical relationships between the different constituent locations to test the application of a precise and refined taxonomy in generating accurate polar biogeographies. Location The Antarctic and sub‐Antarctic region comprising the islands South Georgia, Crozet, Kerguelen, Marion, Heard and the Antarctic Peninsula. Methods Diatom samples from different habitats in a large part of the sub‐Antarctic and Antarctic region were investigated for their Stauroneis content. Presence/absence data were investigated using Sørensen's similarity index. An additional 500 samples from Arctic locations were used to provide a bipolar comparison. Using reliable literature data, gaps in the distribution of the Stauroneis taxa were filled. Results The Stauroneis flora of the Antarctic and sub‐Antarctic regions is quite distinct from its Arctic equivalent, with only five species (out of 60) common to both areas. Within the (sub‐)Antarctic group, the islands of the Indian Ocean have the most diverse Stauroneis composition, which is clearly separated from the rest of the region. The South Georgia Stauroneis composition has some affinities with the Antarctic Peninsula but the latter has far fewer species. These results are in clear contrast to older data showing no biogeographical difference between the Arctic and Antarctic regions. Main conclusions Using only a single genus, a clear biogeography of the (sub‐)Antarctic region can be produced that separates the Indian Ocean islands from other sampling locations. When based on a precise taxonomy, biogeographical relationships between locations in the region become much more reliable. Contrary to previous work, there is almost no similarity in the diatom floras of the Arctic and Antarctic regions.