Protein polymorphism in some brackish-water populations of Gammarus aequicauda and G. insensibilis was assayed by electrophoresis. The analyses for several gene-enzyme systems indicate a low level of genetic variability. The data of repeated investigations show a strong temporal stability of the distribution of heterozygous loci, with a consistently high heterozygosity for the Pgi locus in G. insensibilis. This suggestes that the prevailing adaptive mechanism is based on a higher individual flexibility in more challenging environments. This is achieved through fixation of alleles conferring higher adaptiveness. However, it is possible that some loci can maintain high levels of heterozygosity by interaction of stochastic and directional factors.
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Con il contributo del Ministero per i Beni e le Attività Culturali