Allozyme clines and evidence of strong selection in three loci inMytilus edulisL. (Bivalvia) from Danish waters

Conspicuous differences in allozyme frequencies are found between Mytilus edulis populations from Bornholm in the Baltic and from the Kattegat and the North Sea in three allozyme loci (PGM: phosphoglucomutase; PGI: phosphoglucose isomerase; LAP: leucinaminopeptidase). The allozyme clines between the two areas are nearly coincident for the three loci. In an experiment where a Mytilus sample was introduced into an area with a different genetic composition, strong differential mortality was observed among the transplanted individuals.