Diversity patterns of honey bee (Apis mellifera L.) populations from the Archipelago of the Azores: insights from mtDNA and wing geometric morphometrics

The patterns of genetic diversity of the honey bee (Apis mellifera L.) populations from the Azores are virtually unknown, contrary to other Macaronesian archipelagos such as the Canary Islands and Madeira. In an attempt to fill this gap, a total of 473 honey bee colonies were sampled across the eight islands of the Azores occupied by honey bees, which were then surveyed for mitochondrial DNA (mtDNA) and wing morphometric variation. The mtDNA origin was assessed using a PCR-RFLP technique of the intergenic tRNA-cox2 region, known as the DraI test. Morphological differences in the wing shape among the populations of the different islands were analyzed with the geometric morphometric approach using 19 anatomical landmarks distributed along the wings venation. In addition to the 473 colonies of the Azores, morphometric patterns were assessed on a reference collection comprising 711 colonies of A. m. iberiensis, 11 colonies of A. m. ligustica, and 15 colonies of A. m. carnica. Maternal patterns were reasonably congruent with the morphological patterns obtained with the wings. The DraI test allowed identification of 13 different haplotypes, including a novel one (A64’). Of the 13 haplotypes, ten belong to the African lineage (lineage A), two to the western European lineage (lineage M), and one to the eastern European lineage (lineage C). Among the known African sub-lineages, sub-lineage AIII was the most frequent (62.38 %) and only 3% of sub-lineage AI was found in Faial. The mtDNA data suggest that historical introductions of honey bee colonies in the Azores originated from the northern part of continental Portugal, where a high frequency of haplotypes of sub-lineage AIII ancestry is found. In addition to historical introductions, the maternal patterns of the Azorean populations have seemingly been shaped by recent importations of commercial breeds of C-lineage ancestry, as suggested by the high frequency of C-lineage haplotypes found in Pico, Faial and Graciosa. The results obtained with geometric morphometrics revealed the power of the wing venation to discriminate different populations in the Azores, and also to distinguish them from the subspecies of the reference collection. The wing morphometric patterns showed that, overall, populations from the Azores exhibited a closer relationship with A. m. iberiensis; however some populations, especially those from Graciosa, tend to be clustered closer to A. m. ligustica and A. m. carnica. The founder effect resulting from introductions of A. mellifera in historical times, the particular insular environment, the barrier to gene flow due to geographical isolation, on one hand, and the contemporary human-assisted gene flow associated with beekeeping activity, on the other hand, are non-mutually exclusive factors that have possibly shaped the diversity patterns observed today in the Azores. Key-words: Apis mellifera, honey bees, Azores Archipelago, mtDNA, DraI test, wing geometric morphometrics, introgression FCUP Diversity patterns of honey bee (Apis mellifera L.) populations from the archipelago of the Azores: insights from mtDNA and w ing geometric morphometrics i