Spatial aspects of genetic differentiation of the European chub in the Rhone River basin

Starch-gel electrophoresis was used to examine genetic differentiation at four polymorphic loci in the European chub Leuciscus cephalus from 27 samples and three main areas of the Rhone River basin in France. The Upper Rhone samples appeared to be genetically distinct at locus PGM-2 * from the Lower Rhone and Saone-Grosne samples according to the constant row total-multiple correspondence analysis (CRT-MCA), which allowed the estimation of multivariate F_st equivalents. No difference between Lower Rhone and Saone-Grosne samples was revealed by the global analysis considering the three areas. However, distinct local analyses in the three areas showed that the spatial structure of genetic variability was dissimilar in these last two areas, suggesting a non-equilibrium process under the influence of dams in the Lower Rhone, and isolation by distance in Saone system. Isolation by distance was also suggested for the Upper Rhone samples.