Diatoms define a novel freshwater biogeography of the Antarctic

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