Genetic variability in selected Polish population of Dreissena polymorpha [Pallas] [Bivalvia; Dreissenidae]

Genetic variability of a selected population of Dreissena polymorpha, an invasive species playing a significant role in aquatic ecosystems, was studied. Starch gel electrophoresis was used to analyse 8 enzymatic loci in 200 individuals collected from 20 sites in a lake. The population was found to have 75.0% of polymorphic loci, 2.8 alleles per locus, 3.5 alleles per polymorphic locus, 0.393 coefficient of expected heterozygosity, and 149 genotypes. Zebra mussel clumps were strongly polymorphic; almost every individual had a different genotype. The high polymorphism observed in the D. polymorpha clumps had most likely resulted from external cross-fertilisation and the presence of free-swimming veliger larvae as well as from a considerable heterozygosity of individual bivalves. Genetic variability of the population studied was found to be similar to that of populations inhabiting other Western Pomeranian lakes, including both highly polluted ones and those formed as recently as about 40 years ago. This provides evidence for a mass colonisation of freshwater reservoirs effected by very polymorphic parent populations of D. polymorpha. The literature data on North American zebra mussel populations which invaded that continent about 10 years ago show them to be polymorphic, too, but not as much as European ones