Allozyme evidence of recent genetic shifts in honey bee populations of Italy

The genetic variability in the malate dehydrogenase (MDH) enzyme system was determined in several honey bee populations sampled throughout Italy in the periods 1981–1985 and 1995–1998. Samples from Calabria and Sicily also were evaluated with the esterase (EST) enzyme system, because Est-3 variability had been proposed as a genetic marker for the native Sicilian subspecies, Apis mellifera sicula. In the northern and central areas which make up the majority of the country, Mdh-1 allele distributions were rather homogeneous and no significant differences in allele frequencies were found between the two sampling periods. Also the hybrid zone between A. m. mellifera and A. m. ligustica did not show significant changes in Mdh-1 allele frequencies, although allele distributions are not homogeneous in this area due to the considerable gene flow between the two subspecies. On the contrary, in southern Italy, allele frequencies are now more similar to those of the rest of the country as a result of a wide scale replacement of the local honey bee population with colonies from northern areas after the spread of varroa mites in the 1980s. In Calabria and Sicily we found the same phenomenon, for both Mdh-1 and Est-3 loci, but the Sicilian native honey bee populations were already being replaced by imported A. m. ligustica when we first sampled them.