GENETIC DIFFERENTIATION OF NIPHARGUS-RHENORHODANENSIS (AMPHIPODA) FROM INTERSTITIAL AND KARST ENVIRONMENTS

Electrophoretic variation in proteins encoded by seven presumptive gen e loci was analyzed in four populations of the stygobiont amphipod Nip hargus rhenorhodanensis. The four populations occur in different habit ats, including one in drainage canals, another from sediments of the A in River, a tributary of the Rhone River, and the remaining two occur in a karstic massif (Dorvan, Ain, France) in the epikarstic and at the base level of the massif, respectively. Six of the seven loci were po lymorphic within or among populations, with as many as three electromo rphs segregating at the most variable loci. Significant deficiencies i n the frequency of heterozygotes were common. Genetic divergence betwe en the two populations of the Dorvan Massif and between the two of the Ain River (forest and sediment habitats) was large. This was highly u nexpected, particularly in the case of the two hydrologically connecte d populations of the Dorvan Massif. It is suggested that either low mi gration rates or the presence of ecological barriers to gene flow may result in strong genetic differentiation among local populations of Ni phargus.