Scotia Arc Acari: antiquity and origin

The Scotia Are comprises South Georgia, South Sandwich, South Orkney and So uth Shetland Islands together with the Antarctic Peninsula. Free-living Aca ri of the Scotia Arc contain immigrant and endemic elements. Transport of i mmigrant species to and within the Maritime Antarctic has been via Holocene storms and ocean currents. Most immigrants are Gamasida, Oribatida and Aca ridida while Actinedida dominate the endemic element. Immigrant species on South Georgia share common 'sub-Antarctic' affinities with South Indian and , to a lesser extent, South Pacific Ocean island faunas. In contrast, immig rants to the rest of the Scotia Are and Bouvetoya on the mid-Atlantic Ridge , form a robust 'Maritime Antarctic' Province group. The endemic component is of largely Tertiary origin and, like that of Continental Antarctica, dom inated by a few cosmopolitan families and genera of Actinedida. There are n o bona fide pan-Antarctic species and little evidence that Continental and Maritime Antarctic faunas have a common ancestry, indeed the Continental en demic fauna is entirely montane while that of Maritime Antarctica is coasta l. The presence of common Maritime Antarctic/South Pacific island genera co rroborate die Antarctic Peninsula as being derived from a South Pacific isl and archipelago which collided with Continental Antarctica during the Terti ary period. (C) 2000 The Linnean Society of London.