COLONIZATION OF EUROPE BY 2 AMERICAN GENETIC TYPES OR SPECIES OF THE GENUS MARENZELLERIA (POLYCHAETA, SPIONIDAE) - AN ELECTROPHORETIC ANALYSIS OF ALLOZYMES

Allozyme electrophoresis was conducted in an attempt to identify the o rigin of Marenzelleria sp. found in the North Sea and Baltic Sea. The analysis covered eight enzymes with ten loci from nine populations fou nd on the North American Atlantic coast, three populations in the Nort h Sea and five populations in the Baltic. The North Sea spionids corre spond to the Type I Marenzelleria from North American coastal waters b etween Barnstable Harbor (Massachusetts) and Cape Henlopen (Delaware). Nei's genetic distance between these North American populations and t hose from the North Sea was D = 0.010 to 0.020. The Marenzelleria sp. found in the Baltic Sea very probably stems from North American popula tions of Type II found from the region of Chesapeake Bay (Trippe Bay) south to the Currituck Sound (North Carolina). The genetic distance be tween these North American populations and the Baltic populations is D = 0.000 to 0.001. The invaders appear to have lost little of their ge netic variation while colonizing the North and Baltic Seas. Probably, both colonizing events call be attributed to large numbers of individu als reaching Europe simultaneously on one or more occasions. In additi on, a Marenzelleria Type III was found by electrophoresis among specim ens from Currituck Sound (North Carolina), where it is sympatric with Marenzelleria Type II. Salinity is discussed as an important factor fo r the establishment of Marenzelleria Type I in the North Sea and Type II in the Baltic Sea.