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S.D. Stepanjants et al.: "A review of bipolarity concepts: History and examples…"

A review of bipolarity concepts: History and examples from Radiolaria and Medusozoa (Cnidaria)
Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory,
University of Copenhagen, Denmark
(Accepted 18 April 2006; Printed 24 July 2006)
ISSN 1745-1000 print/ISSN 1745-1019 online
Marine Biology Research, 2006; 2: 200-241
Zoological Institute, Russian Academy of Sciences, St Petersburg, Russia, Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany, P.P. Shirshov Institute of Oceanology, Russian Academy of Sciences, Moscow, Russia & Natural History Museum, Department of Geology, University of Oslo, Norway
Bipolarity, its history and general interpretation are investigated and discussed herein. Apart from the classical view, namely that a bipolar distribution is a peculiar biogeographical phenomenon, we propose that it is ecologically controlled too. This approach was used for bipolarity assessment within the following groups: Phaeodaria, Nassellaria, Spumellaria (Radiolaria) and Medusozoa (Cnidaria). We recognize 46 bipolar radiolarian species and three radiolarian genera. However, although species concepts in radiolarians are relatively stable and well known, the high-rank taxonomy of radiolarians is still not well defined. Caution should therefore be taken in the interpretation of distribution data at a taxonomic level higher than the species. In the Medusozoa, bipolarity is observed for 23 species and 32 genera. The different ways in which bipolarity can develop are discussed under the different groups, but preference has been given to the recent and most probable routes of migration. In our investigation of the bipolarity phenomenon, we reviewed more than 400 articles dealing with taxonomy, ecology and biogeography of the modern fauna in both groups.
Key words: Biogeography, bipolarity, Medusozoa, Radiolaria

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