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.
The mosquito Culex pipiens is subjected to organophosphate treatments in both Corsica and southern Sardinia, but the resistance gene A2‐B2, which is currently in a worldwide expansion, has only reached Sardinia. In order to understand this situation, the genetic structure of populations sampled in Sardinia and Corsica was assessed using 15 isozymes. Two loci (HK1 and HK2) were not taken into account because of the possibility of selection. For trie other loci, statistical independence was not rejected for all possible pairs, and no deviation from Hardy‐Weinberg expectations was apparent. Low but significant genie differentiation was present between Corsica and Sardinia, as well as between northern and southern Sardinia, despite a large number of effective migrants per generation. These results are discussed in the context of the high probability of extinction/recolonization of breeding sites, the flight migration ability of this mosquito, and the pleiotropic cost of insecticide resistances genes. It is concluded that A2‐B2 resistance is unlikely to reach Corsica from southern Sardinia, unless accidental human transportation occurs.
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