Latitudinal variation of allozyme frequencies in populations of 2 fresh-water isopods in western-europe

Populations of the freshwater isopods, Proasellus meridianus Racovitza and P. coxalis Dollfus were found to be polymorphic at loci coding for the enzymes glucose phosphate isomerase (GPI) and phosphoglucomutase (PGM). PGM allele frequencies in populations of both species were significantly associated with latitude as has been previously reported for the closely related Asellus aquaticus (L.). Co-variation of PGM allele frequencies was also found in sympatric populations of P. meridianus and A. aquaticus. Significant interpopulation variation in GPI allele frequencies occurred in P. coxalis but not P. meridianus, however, this variation was not associated with latitude.