Systematics and biogeography of marine gastropod molluscs from South Georgia Diego G. Zelaya Zelaya, D. G. (2005): Systematics and biogeography of marine gastropod mol-luscs from South Georgia. -Spixiana 28/2: 109-139 The gastropod fauna of South Georgia is reviewed and a complete list of the 121 species known from the archipelago is provided; 65 species were re-examined upon the study of 3047 specimens and reference specimens illustrated; other 56 species were inchided in the list from literature records. lotliia coppingeri (Smith, 1881), Submargarita unißlosa Thiele, 1912, Eiimetiila dilecta Thiele, 1912, Omalogyra burd-woodiana Strebel, 1908 and Neumesia antarctica Smith, 1902 are reported for the first time from South Georgia, and the presence of 16 species is confirmed by a second finding. Moreover, new bathymetric ranges for 30 species are given. The analysis of faunistic affinities of the gastropod fauna from South Georgia revealed a high similarity with South Orkney Islands (35 %), the Antarctic Weddell Sector (35 %) and South Shetland Islands (32 %). These data suggest the placement of the South Georgia in the Antarctic Region. However, the high number of gastro-pod species only known from South Georgia (53 species, 43 % of the total) and the distinctiveness of the composition of their assemblages, suggest that South Georgia should be considered as an own section within the Antarctic Region. Diego G. Zelaya, Division Zoologia Invertebrados, Museo de La Plata, Paseo del Bosque s/n, 1900 La Plata, Buenos Aires, Argentina; e-mail:
[email protected] Introduction In recent years, an increasing number of studies on the benthic invertebrate fauna from the Southern Ocean have been conducted; however, the gastro-pods from South Georgia (53°58'-54°55'S, 35°42'-38°20' W) remain scarcely studied. The first contribu-tion to malacology in the archipelago was con-ducted by Martens (1885), who reported 34 species of gastropods, 10 of them new to science. Martens & Pfeffer (1886) reported 39 species of gastropods (21 new), most of them were not figured. Contribu-tions by Lamy (1911), Dali (1914), David (1934) and Dell (1990) provided new localities for some species within the archipelago. The most significant contri-butions were based on collections made by the Schwedische Südpolar Expedition (Strebel 1908), and the Discovery, Discovery II and William Scores-by Expeditions (Powell 1951). From them, 62 new species were described. Subsequently, Carcelles (1953) provided additional locality data for 27 gas-tropods from South Georgia and listed all nominal gastropod species reported from Antarctica (includ-ing South Georgia). The relatively few malacological studies related to South Georgia contributed to the existing contro-versy about their biogeographic position (Clarke 1996). In a faunistic point of view, South Georgia were considered as being related to both Magellan (Linse 1997) or Antarctic Regions (Carcelles 1953, Zelaya 2000), as representing a transitional area between these regions (Linse et al. 2003, Schrödl 1999, 2003), or as a distinctive biogeographic unit (Linse 2002, Powell 1951); also, some workers argued on its faunistic affinities with Kerguelen Islands and Crozet Islands (Canteras & Arnaud 1985). In the present paper, the diversity of the gastro-pods from South Georgia (except pteropods) is critically reviewed, and the faunistic affinities and the biogeographic position of the archipelago are re-examined. 109
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