Diatoms define a novel freshwater biogeography of the Antarctic

Abstract

Terrestrial biota in the Antarctic are more globally distinct and highly structured biogeographically than previously believed, but information on biogeographic patterns and endemism in freshwater communities is largely lacking. We studied biogeographic patterns of Antarctic freshwater diatoms based on the analysis of species occurrences in a dataset of 439 lakes spread across the Antarctic realm. Highly distinct diatom floras, both in terms of composition and richness, characterize Continental Antarctica, Maritime Antarctica and the sub-Antarctic islands, with marked biogeographic provincialism in each region. A total of 44% of all species is estimated to be endemic to the Antarctic, and most of them are confined to a single biogeographic region. The level of endemism significantly increases with increasing latitude and geographic isolation. Our results have implications for conservation planning, and suggest that successful dispersal of freshwater diatoms to and within the Antarctic is limited, fostering the evolution of highly endemic diatom floras.

Fifty million years of beetle evolution along the Antarctic Polar Front

“…Both regions share many higher taxa (e.g., ref. 25), a dynamic geo-climatic history (6,26), a profound degree of isolation, and indications that climatic events likely structured their biota (6,8,27). The terrestrial habitat on the continent and its surrounding islands is fragmented by large expanses of ice or ocean, respectively, and has been further isolated by the Antarctic Circumpolar Current for at least 34 Ma (28,29).…”

“…In contrast, Antarctica's paleoclimatic legacy for terrestrial communities has long been considered one of widespread extinction due to glaciation. Evidence of terrestrial species surviving in Antarctic glacial refugia (6) and discoveries of substantial endemic diversity and biogeographic structuring in some groups (7,8) is changing this narrative, indicating extended evolutionary histories on land. Yet, such evolutionary histories remain obscured by a lack of large-scale molecular phylogenetic work, with most Antarctic terrestrial research focused on small subsets of species or populations (9,10).…”

“…The hypothesis that diversification has proceeded similarly in Antarctic marine and terrestrial groups has not been tested. While the extinction of a diverse continental Antarctic biota is well established (13), mounting evidence of significant and biogeographically structured Antarctic terrestrial diversity (8,14,15) with a long evolutionary history (6,16) suggests the possibility of broadly similar diversification processes across marine and terrestrial Antarctic systems. If valid for some taxa, further tests should then be sought across a wider variety of organisms.…”

Comparative phylogeography reveals consistently shallow genetic diversity in a mitochondrial marker in Antarctic bdelloid rotifers

“…Terrestrial habitats are highly fragmented, interrupting migration and gene flow (Bergstrom & Chown, 1999; Chown & Convey, 2007; Convey et al, 2014). Biogeographical regionalisation is thus known to occur (Terauds et al, 2012; Verleyen et al, 2021), with genetic structure between populations and species even across relatively small areas (Carapelli et al, 2020; McGaughran et al, 2019; de Wouw et al, 2007).…”

From the Heroic Age to today: What diatoms from Shackleton's Nimrod expedition can tell us about the ecological trajectory of Antarctic ponds

“…Diatoms (Bacillariophyceae), siliceous unicellular microeukaryotic algae, make excellent bioindicators due to their species-specific environmental preferences, ease in morphological identification, and excellent preservation (Smol and Stoermer 2010). They are especially useful in Antarctica where the continental flora consists of $ 50 mostly endemic species (Esposito et al 2008), and is distinct from the Maritime-and sub-Antarctic regions (Verleyen et al 2021). Reports on Cape Royds diatom communities are few, and largely consist of survey descriptions and checklists by West and West (1911), Fukushima (1964Fukushima ( , 1967, and Broady (1989).…”