NEW MARINE DIATOM (BACILLARIOPHYTA) SPECIES DESCRIBED FROM KERGUELEN ISLANDS COASTAL AREA AND PERTAINING TO NAVICULA S.S. WITH SOME REMARKS ON MORPHOLOGICAL VARIATION OF THE GENUS

Islands far from continental influence or impact represent an interesting field of investigation with regard to species diversity, morphological evolution and speciation. Austral Islands represent such a case, particularly for diatoms (Bacillariophyta). Several light (LM) and electron (SEM) microscopic surveys revealed the presence of more than 20 species, and possibly two genera, new to science. These new species pertain to several genera, most of them belonging to Navicula s.s. and Opephora, with respectively, eight and four new species. In this paper we describe only the new Navicula s.s. taxa, which are: Navicula australoceanica, N. concordia, N. criophiliforma, N. fabiformis, N. hippodontaformis, N. irminae, N. papilioarea and N. szlachetkoi. If we include historical data, e.g., works of Heiden & Kolbe, and recent data of Le Cohu & Maillard, Riaux-Gobin & Compere and Riaux-Gobin & Romero, the number of species described from Kerguelen Archipelago increases to several dozen. Therefore, it appears that the marine littoral of the Kerguelen Archipelago may represent a biodiversity hot spot. The factors (selection pressure) helping to generate this unique flora may be the geographic isolation of these islands and the unique hydrologic features, including being surrounded by strong hydrologic fronts, e.g., Polar and Sub-Polar Fronts.

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