An illustrated and annotated checklist of freshwater diatoms (Bacillariophyta) from Livingston, Signy and Beak Island (Maritime Antarctic Region)

Background and aims - Non-marine diatom communities in the Antarctic Region are characterized by a typical species composition, dominated by a large number of Antarctic endemic species. Despite recent advances in our knowledge about the diversity and biogeography of non-marine Antarctic diatoms, the flora of many Antarctic localities is still only poorly known, which can result in incorrect conceptions of species' distributions. The present paper provides a taxonomically consistent illustrated checklist of the diatom flora observed in recent and (sub)fossil non-marine sediments of three islands in the proximity of the northern Antarctic Peninsula, namely; Signy Island (South Orkneys), Livingston Island (South Shetlands) and Beak Island (James Ross Island group). Methods - The diatom flora of 66 samples collected from a wide variety of lakes and localities on the three above-mentioned islands has been studied using light and scanning electron microscopy. The biogeographical distribution of the composing taxa has been assessed on the basis of quality-checked distribution data from the recent literature. Key results - One hundred and two diatom taxa, belonging to thirty-four genera, were observed. Pinnularia (twelve taxa), Chamaepinnularia, Luticola, Planothidium, Psammothidium and Stauroneis (seven taxa each), Nitzschia (six taxa), Humidophila and Navicula (five taxa each) proved to be the most species-rich genera. Original morphometric data (including length, width and stria density) and illustrations are presented for all taxa observed. Forty-one species are hitherto only known from the Antarctic region. The exact taxonomic identity of twenty species remains uncertain and requires further study. It is suspected that many of these will also turn out to be restricted to the Antarctic region, suggesting that about half of all taxa observed are probably endemic to the Antarctic. Conclusions - The diatom flora of the three investigated localities comprises a large proportion of typical Antarctic taxa, many of which have only recently been split off from their presumably cosmopolitan relatives.