A review of bipolarity concepts: History and examples from Radiolaria and Medusozoa (Cnidaria)

Abstract

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.

Keywords:

• Biogeography
• bipolarity
• Medusozoa
• Radiolaria

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark

Acknowledgments

We are thankful to all investigators who collected and organized the radiolarian and cnidarian material, and worked fruitfully on its taxonomy. This has made it possible to undertake interpretations on the bipolarity problem. We are thankful to our colleagues Dr B. I. Sirenko and Dr A. F. Emeljanov (Zoological Institute RAS, St. Petersburg), Dr A. I. Kafanov (Marine Biology Institute, Vladivostok), Dr D. Boltovskoy (University of Buenos Aires), Dr Stanley Kling (Scripps Institution of Oceanography, La Jolla) and Dr Oliver R. Anderson (Lamont-Doherty Earth Observatory, Palisades) for reading the manuscript and for their critical advice on its first version. Mr B. F. Anokhin (ZIN RAS) helped in preparing the figures. We are grateful for the critical and stimulating remarks and suggestions from the reviewers.

The present investigation was supported by the Russian Foundation of the Fundamental Researches (grants N 97-65-685, N 01-05-64-478), the Norwegian Research Council for Science and the Humanities, and the Nansen Foundation (Norwegian Academy of Sciences) for radiolarians (Kruglikova); by the Federal Programme “World Ocean” of the subprogram “Antarctic Fauna”, Project N16 “Antarctic Biota”, and the Nansen Foundation (Norwegian Academy of Sciences) for the Medusozoa (Stepanjants); by the Deutsche Forschungsgemeinschaft as part of the DFG-Research Center “Ocean Margins” of the University of Bremen, no. RCOM0395 (Cortese); by the Norwegian Research Council for Science and the Humanities, and the Natural History Museum, University of Oslo (Bjørklund).

Notes

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark