A map of the distribution of Apis mellifera mitochondrial DNA lineages in Italy

Two Apis mellifera subspecies have been described to be native and endemic to Italy: A. m. siciliana (A lineage), originally populating Sicily and surrounding minor islands, and A. m. ligustica (C lineage), known as the Italian honey bee and widespread along the Peninsula. Other two subspecies have been reported mainly in border regions: A. m. carnica (C lineage), mainly described in the North-East regions of Italy, and A. m. mellifera (M lineage), mainly reported in the North-West borders and in several Alp valleys. Movements of honey bee populations due to beekeeping activities and crossbreeding programs have contributed, more recently, to distribute different lineages and hybrids all over Italy. In this study, we produced a first comprehensive map of the distribution of the three main mitochondrial A. mellifera lineages (A, C and M) along the Italian Peninsula, Sardinia and Sicily. The study took advantage of the possibility to analyse honey bee DNA recovered from honey. A total of 549 honey samples produced by different beekeepers in all Italian regions were included in this study. DNA was extracted from these samples and amplified using an optimized PCR protocol for degraded DNA. This PCR method was developed to detect a specific informative region of the honey bee mitochondrial DNA (mtDNA). Then, PCR products were subject to gel electrophoresis to assign the corresponding mitotypes. Several DNA fragments were also sequenced to confirm the expected sequence. The most frequent mtDNA lineage in all Italian regions was lineage C with the exception of Sicily, where the most frequent mitotype belonged to lineage A. Sicily was also the region in which the A lineage was found with the highest percentage among all other investigated regions or provinces (>60%). This result confirms the African origin of the Sicilian original A. mellifera genetic stock. Lineage M was observed in most regions but it was never the prevalent mitotype. This work provided the most recent and updated assessment of the diffusion of different mtDNA lineages in Italy. The results obtained can be useful to support conservation programs of different honey bee subspecies in Italy.