A comparative study on enzyme polymorphism in sympatric diploid and triploid forms of Lumbricillus lineatus (Enchytraeidae, Oligochaeta)

Polymorphisms in the phosphoglucose isomerase and phosphoglucomutase loci are studied in sympatric diploid and triploid Lumbricillus lineatus (O.F.M.) from 13 stations. The frequency of identical phenotypes is very similar in the two forms within the majority of stations. It is concluded that natural selection is responsible for the variation. The identical distribution of phenotypes in the diploid and triploid form suggests a situation where selection favours a certain distribution of phenotypes in a given environment and without unconditioned superiority of any phenotype.