The immigration of glacial relicts into Northern Europe in the light of recent geological research

Abstract

Until 1957 glacial relicts (mostly crustaceans) of the Baltic Sea and lakes of Northern Europe were suggested to have reached the area from Siberian coastal waters via the ocean. Then, however, the author concluded that a marine route was unacceptable, and that the relicts had invaded Northern Europe along a continental freshwater path (S. G. Segerstråle, Commentat. Biol. Soc. Sci. Fenn. 16, 1957). This path came from West‑Siberian ice­-dammed waters into which marine animals, the coming relicts or their ancestors, had been trapped when the ice sheet advanced southwards across Siberian coastal waters and, by blocking rivers, gave rise to an enormous lake system. Crossing the Urals and migrating westwards along ice‑dammed waters, the relicts invaded Northern Europe. In this invasion a freshwater crustacean of Baikalian origin also took part, thanks to its inclusion in the West‑Siberian system of proglacial lakes. Recent geological work convincingly speaks in favour of this theory.