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    THE ROSS SEA AS A UNIQUE EVOLUTIONARY SITE

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    Document Number:
    WG-EMM-09/13
    Author(s):
    J.T. Eastman and D.G. Ainley (USA)
    Abstract

    The case is made that the Ross Sea is an evolutionary site on par with those of the Galápagos, Hawaii, Madagascar, the African Rift Valley lakes, and Lake Baikal, all recognized as World Heritage Sites. The focus herein will be on notothenioid fishes because their taxonomy and phylogeny are reasonably well known, and have been more thoroughly studied from an evolutionary perspective than many other Antarctic marine groups. The Ross Sea fish fauna includes 95 species of fishes, dominated by 61 species of notothenioids, an endemic perch-like group. Relative to fish fauna in warmer regions, the nature of the Ross Sea fish diversity overshadows the absolute numbers of species. Antarctic notothenioid fishes, living at subzero temperatures possess blood antifreeze and lack hemoglobin; moreover, lacking a swim bladder, they have repeatedly diversified into water column niches where they dominate abundance and biomass. As the Ross Sea continental shelf was not entirely covered by a grounded ice sheet, which was true of almost the entire remainder of Antarctic shelves during the most recent glaciations, it also constitutes an evolutionary refuge, so far, relatively untouched by direct human influence. The adaptive radiation involved, therefore, is unique and should be further investigated, including the ecological interactions among species and the environment, in its natural state.

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