GENETIC POPULATION-STRUCTURE OF THE POSTGLACIAL RELICT DIVING BEETLE HYDROPORUS-GLABRIUSCULUS AUBE (COLEOPTERA, DYTISCIDAE)

The genetic population structure of the diving beetle Hydroporus glabriusculus was investigated by studying electrophoretic variation at nine enzyme loci. H. glabriusculus is a boreal Palaearctic dytiscid occurring in the far north of Eurasia and as scattered colonies elsewhere in western and central Europe, where it is considered to be a remnant of the early Postglacial biota. Analysis of allele frequency variation revealed considerable population substructuring within localities, which was supported by the field observation that the species exists as small, discrete colonies within a fen habitat showing considerable micro-ecological variation. This appears to be the first time such a demic population structure has been reported in a fully aquatic freshwater organism.