Abstract
The Joint Magellan Victor Hensen Campaign in 1994 focused on the biogeographic relationships of the Antarctic and Magellan fauna. The Peracarida and Mollusca sampled at 18 stations in the Beagle Channel by means of an epibenthic sledge were compared with the knowledge about the distribution of species data from the Falkland Islands, South Georgia, Antarctica and the Kerguelen. Peracarida were an important fraction of the macrobenthos and sampled in high numbers. About 105,000 individuals were collected with the epibenthic sledge. Until now about 40 species of Amphipoda, about 42 species of Isopoda, 24 species of Cumacea, eight species of Mysidacea, and 16 species of Tanaidacea were found. 118 mollusc taxa were identified, nine species of Aplacophora, 52 of Gastropoda, five of Scaphopoda and 52 of Bivalvia. Although the species present different distribution trends, the zoogeographic comparison for six larger taxa (four Mollusca and two Peracarida) showed that the species similarities decreased from the Magellan region towards the Falkland Islands and from South Georgia to Antarctica. The Magellanic Gastropoda showed similarities with the fauna of the Falkland Islands and South Georgia (31-37 %), whereas the Bivalvia were more similar to the Antarctic fauna (29 %). With regard to Crustacea, 10% of Antarctic Isopoda species were also found in the Magellan region; the Weddell Sea and East Antarctica, and South Georgia and the Antarctic Peninsula shared most species of both Cumacea and Isopoda, whereas the lowest similarities were shown between Bellingshausen and Weddell Sea for the Isopoda, and interestingly between the Magellan region and South Georgia for the Cumacea. The highest degree of endemism of the Isopoda and Cumacea was found in the Magellan region, where as a consequence of the opening of the Drake Passage many new species seem to have evolved in these taxa.
Highlights
The highest degree of endemism of the Isopoda and Cumacea was found in the Magellan region, where as a consequence of the opening of the Drake Passage many new species seem to have evolved in these taxa
The zoogeography of the fauna of the Magellan region is important with respect to the Antarctic faunal composition, as South America was the last continent that separated from Gondwana some 30 to 20 my ago (Kennett, 1977; Crame, 1992)
Crustacea Peracarida and Mollusca were collected with an epibenthic sledge (EBS), which was modified after Rothlisberg and Pearcy (1977), at 18 stations in the Beagle Channel
Summary
The zoogeography of the fauna of the Magellan region is important with respect to the Antarctic faunal composition, as South America was the last continent that separated from Gondwana some 30 to 20 my ago (Kennett, 1977; Crame, 1992). To what extent the presence of species corresponds between the Magellan area, the islands of the Scotia Arc, the Antarctic Peninsula and the high. Antarctic, is of utmost interest for biogeographic and evolutionary questions, The first investigations in the Magellan region, especially in the Beagle Channel date back to the. Antarctic Expedition (Melvill and Standen, 1907, 1912), the “Albatross” (Dall, 1908) and the “Discovery” (Powell, 1951; Dell, 1964). The most extensive and recent accounts of the Antarctic macrofauna and special macrofaunal taxa have been published recently, after modern research vessels, such as RV “Polarstern” were used for the logistics (e.g. Voß, 1988; Mühlenhardt-Siegel, 1989; Hain, 1990; Rauschert, 1990; Brandt, 1991). In the Magellan area fewer recent investigations have been undertaken mostly on special macrofaunal groups In the Magellan area fewer recent investigations have been undertaken mostly on special macrofaunal groups (e.g. Winkler, 1994; Linse, 1997; Schrödl, 1997)
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