Genetic variation in the stygobite amphipod Niphargus rhenorhodanensis: Comparison of four hyporheic populations of the Rhône and the Ain Rivers (France)

Abstract

Electrophoretic allozyme analysis was performed on the stygobite amphipods Niphargus rhenorhodanensis collected from the sediments of four locations, three on the River Rhone and one on its tributary, the River Ain. Six enzymes, encoded by seven presumptive loci, were examined. Four loci were monomorphic, while three were polymorphic, with three alleles segregating at the AO, GPI and EST loci. The four populations seem to belong to a panmictic unit, with little genetic differentiation among populations. Thus, gene flow among populations does not appear to be impeded by either geographic distance (15 to 60 km) or the presence of dams on the River Rhone. At the scale of the study, and with this method, an ancestral genetic unit seems to have existed for the individuals of the Rhone and Ain Rivers, owing to recolonization after the last glaciations (12,000 years ago), but homogenization of genetic patterns may also have resulted from extensive migrations not expected according to the biology of this stygobite species.