Electrophoretic analysis of 17 enzyme loci was carried out to assess the genetic differentiation and isolation of the Sardinian Polyommatus coridon gennargenti from R c. apennina of peninsular Italy and the related taxon P caelestissimus from central Spain. I? c. gennargenti is represented by a small, strongly inbred population, restricted to the central mountains of Sardinia, and probably derived from mainland populations as indicated by the reduction of genetic variation (P 17.6 per cent, H 0.024) with respect to the continental populations (P>52 per cent, H 0.170). Absence of gene flow is indicated by the presence of alternative fixed alleles at the Aat, Gpi and Pgm loci and significant differences in allele frequencies at other loci, which distinguish the Sardinian population from 1? C. apennina and P caelestissimus. The genetic differentiation of P c. gennargenti, as measured using Wright's FST values and Nei's genetic distances, suggests the evolution of the Sardinian taxon along an independent lineage, facilitated by isolation and the strict dependence of the butterflies on specific biotopes, thus confirming its taxonomic status.

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