Clone pool structure of four ecologically dissimilar parthenogenetic earthworms (Lumbricidae) was studied by means of enzyme electrophoresis in Sweden, Finland and Estonia. Each Octolasion cyaneum population had only one clone (=electrophoretic overall phenotype) but the clones differed from each other. Separate populations probably originate from one or few founder worms or cocoons unintentionally introduced by man. In Aporrectodea rosea the clonal heterogeneity was high. This is probably due to a high rate of unintentional in addition to parthenogenetic ones. Sweden and Estonia share 38% of the A. rosea clones and 49% of the A. rosea individuals with the same genotype whereas the corresponding figures between Finland and Estonia and between Finland and Sweden were lower. There is evidently some clone flow between the countries. These inter-regional clones are most probably southern immigrants into the area. The clone pool diversity of two epigeics namely Eiseniella tetraedra and Dendrobaena octaedra was high but clone pool similarities between the countries were, on average, lower than they were in A. rosea. In E. tetraedra the highest similarity was found between Finland and Sweden but in D. octaedra between Sweden and Estonia as well as Finland and Estonia. These differences can be explained by the different post-glacial dispersal patterns of the clones. Intraspecific differences in somatic traits and secondary reproductive organs between the countries were found, too. The study shows that parthenogenetic earthworms with a continuous geographical range by the Baltic Sea actually comprise populations which differ considerably in their genetical make-up and morphological and morphometric traits. The differences can best be explained by dissimilar post-glacial immigration and adaptation.
