Clone pool diversity was studied in two parthenogeneticOctolasionspecies in South Finland belonging to the region of Fennoscandia where the species occur at the northern margin of their European range. In spontaneously dispersingO. tyrtaeumwe recorded 24 clones (238 individuals/8 localities), but in anthropochorously dispersingO. cyaneumonly two clones (134 ind./4 locs.) were found. InO. tyrtaeumthe clone pools of the East ( = sample region) and the North were more similar to each other than to that in the West. Clone groups showed a clinal distribution pattern, which suggests that they may be adapted to regional environments. The low clonal heterogeneity ofO. cyaneumis attributed to a small founder population and clonal drift. Morphological variability showed that characters related to reproductive organs vary extremely little in the two species. Considering somatic characters, segment number seemed to be mostly controlled by the genotype, whereas body size varied mostly according to the locality and region implying the role of environmental variables. In the North,O. tyrtaeumadults were larger than their counterparts in the East and the West.