Mitochondrial DNA variability in honeybees and its phylogeographic implications

Abstract - A physical map of mitochondrial DNA (mtDNA) of the honeybee (Apis mellifera L) has been established with 17 restriction enzymes (46 sites). Elements of the genic map have been inferred from sequence data. The superimposition of both maps indicate that the gene order is quite similar between honeybee and Drosophila. The total length of the mitochondrial genome falls between 16 500 and 17 000 bp. This range is due to several regions exhibiting length polymorphisms. Two of them overlap with the control region, but a third one is unexpectedly located between the CO-I and CO-II genes. This last polymorphism is explained by the occurrence of variable numbers of 2 related sequences, called P and Q, which arose through tandem duplication. Sequence data from 3 regions of the mtDNA genome can be used to infer a phylogenetic tree for 4 Apis species: the resulting tree topology, (florea(dorsata(cerana,mellifera))), confirms the phylogeny based on morphometry and behavior. The mtDNA variability of Apis mellifera indicates 3 major lineages: African colonies (lineage A) including intermissa, adansonii, scutellata, capensis and monticola subspecies; mellifera colonies (lineage M); ligustica, carnica and caucasica colonies (lineage C). This distribution is very similar to the 3 evolutionary branches inferred from morphometric analysis by Ruttner. The main difference concerns the branch M which, according to Ruttner, includes also intermissa and iberica. From an Asian origin, 3 evolutionary branches colonized respectively northern Europe (M), the north-Mediterranean region (C) and Africa (A). Based on the Drosophila evolutionary rate, this divergence would have occurred between 300 000 and 1300 000 bp.