Antarctic ascidians: an isolated and homogeneous fauna

• Published in: Polar Research
• Main Authors: Primo, C, Vazquez, E
• Format: Article in Journal/Newspaper
• Language: English
• Published: Norwegian Polar Inst 2009
• Subjects: Biological Sciences; Evolutionary Biology; Biogeography and Phylogeography; Antarctic; Bellingshausen Sea; Sandwich Islands; The Antarctic; Antarc*; Polar Research
• Online Access: https://doi.org/10.1111/j.1751-8369.2009.00110.x; http://ecite.utas.edu.au/64422

Several biogeographical studies have already been performed on the ascidiansof the Antarctic region. However, new data obtained in the last few years haveled us to a revision of the biogeography of this fauna. To examine the biogeographicalstructure of the Antarctic region, we divided it into 10 sectors,depending on the principal geographical features, and then applied clusteranalysis and a multi-dimensional scaling ordination to a presence/absencematrix of species for each biogeographical area. Our study shows that Antarcticascidians are a very homogeneous fauna, with a high level of endemism in thewhole region (2551% of Antarctic endemic species per sector), but with a lowpercentage of sector endemism (only up to 10%). This probably results fromisolation arising from the Antarctic Convergence, and the vast geographicaldistances from adjacent regions, as well as from the relative constancy of thehydrographical conditions and the dispersal of organisms through circumpolarcurrents. In fact, cosmopolitan species represented only 07% of the totalascidian fauna in all sectors. Only the Bellingshausen Sea (low sample size),Bouvetya (young and isolated, with an impoverished ascidian fauna) and theSouth Sandwich Islands (also young and isolated) are relatively separated. Theinsular sectors were more closely related to the South America and sub-Antarctic regions than the continental ones, showing a latitudinal gradient.