MOLECULAR TIME SCALES FOR EVOLUTION IN MYSIS AND PONTOPOREIA

The results of recent allozyme studies addressing the controversial hypotheses on the origin of the 'glacial relict' crustacean species in Europe and North America are reviewed. The data suggest that the time since the divergence of the lineages leading to each of the three currently recognized Pontoporeia species (P. affinis, P. hoyi, P. femorata) is of the order of tens of million years; this is in sharp contrast to recent suggestions of a late Pleistocene descent of both the European and North American freshwater species from the marine P. femorata. The divergence of the Mysis relicta lineage from its present marine congeners is probably younger but also dates back to the Tertiary. M. relicta itself comprises a group of several distinct species, two of which coexist in the Baltic Sea.