Maternal structure of Iberian honey bees inferred from whole mitochondrial genomes

The maternally inherited mitochondrial DNA has been the marker of choice for assessing Iberian honeybee variation, particularly the intergenic tRNA^leu-cox2 region. The data generated by massive sampling of this region confirmed early findings of coexistence of African (A) and western European (M) lineages, forming a south-north cline, and revealed unparalleled levels of haplotype diversity and complexity. Accordingly, it has been suggested that Iberia served as a glacial refuge, and as a place of secondary contact between European and African lineages. While we have learned a great deal with this region, due to its high levels of variation and repetitive structure, there are evolutionary questions that can only be properly addressed using other mitochondrial regions. In this study, we used NGS technology to sequence the whole mitogenomes of 70 A.m. iberiensis, 7 A.m. intermissa, 7 A.m. sahariensis, and 8 Am. mellifera. The data was analyzed using a phylogeographical framework to address the following questions: When did M and A lineages split? How divergent are African-derived Iberian honey bees from both African subspecies? Is there evidence of multiple range expansions of northern African honey bees? Which African subspecies is the most probable source of African genes in Iberian honey bees? The powerful data set generated in this study is providing the opportunity to decipher the Iberian honey bee history at an unprecedented resolution. At the same time, it will supply a strong scientific basis for conservation decisions, which is increasingly important in face of the escalating threats to honey bee diversity.