The taxonomic status, the possible hybridization in nature and the genetic variability of Apodemus sylvaticus and A. flavicollis has been investigated using the electrophoretic analysis of 30 enzyme loci in field populations of both species, living sympatrically in the Tolfa hills (North-West of Rome). The results obtained show: 1) A. sylvaticus and A. flavicollis are reproductively isolated and genetically well-differentiated species, easily and surely identifiable by electrophoresis; 2) in the area studied four enzyme loci (Ldh-1, Me-1, Ipo-1 and α-Gpdh) are diagnostic between A. sylvaticus and A. flavicollis, while three others (Idh-1, 6-Pgdh and Est-2) are partially discriminating as the common alleles are different in the two species; 3) average genetic distance (D) between the populations of A. sylvaticus and A. flavicollis studied is 0.2029 (I — 0.8163); 4) the mean heterozygosity per locus observed was 0.035 in A. sylvaticus and 0.020 in A. flavicollis; 5) no hybrids were observed in the area studied and habitat isolation appears to be an important factor in reproductive isolation; 6) the occurrence of introgression in the area studied cannot be completely excluded on the basis of the electrophoretic data; 7) comparison of A. flavicollis from the Tolfa hills with populations of the same species from the Western Alps and Central Apennines North of Tolfa showed considerable genetic differences, confirming the existence of distinct subspecies of A. flavicollis in Italy.
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Con il contributo del Ministero per i Beni e le Attività Culturali