Origin and evolution of honey bees
The origin of the Western honey bee lies in the Middle East, where it originated among other Apis-species around 6 to 9 million years ago. About a million years ago, the honey bee (Apis mellifera) finally spread from Asia to Africa and Europe while it had to adapt to the new environmental conditions. This adaptation process has resulted in four major evolutionary lineages of Apis mellifera: the M-lineage (Western and Northern Europe), the C-lineage (Eastern Europe), the O-lineage (Middle East and Central Asia) and the A-lineage (Africa). The natural distribution range of the honey bee extends from the southern tip of Africa over savannah, rainforest, desert, Mediterranean to southern Scandinavia. With such a variety of habitats, climatic conditions, flora and fauna it is not surprising that numerous subspecies have emerged, each possessing special traits to optimally adapt them to their local habitat. Today more than 28 honey bee subspecies have been described. These subspecies are genetically different and can therefore be distinguished by means of DNA analyses.
Situation in Switzerland
In Switzerland there are currently four subspecies or races of the honey bee: the original native dark honey (Apis mellifera mellifera), the Carnica bee (Apis mellifera carnica), the Italian bee (Apis mellifera ligustica) and the Buckfast bee (hybrid breed). The dark Mellifera honey bee belongs to the evolutionary M-lineage, while Carnica and Ligustica are part of the C-lineage. Buckfast bees are closely related to the Ligustica subspecies and therefore mainly belong to the C-lineage. Since the subspecies of the C and M evolutionary lineages are very clearly genetically differentiated, it is possible to draw highly accurate conclusions about the hybridization between the two groups using only very few genetic markers.
What are SNPs?
A genome is the entirety of the genetic information of any organism. This genetic information is encoded in the DNA of each cell by a sequence of four nucleic acid bases: A, T, G and C (letters of the genetic code). The honey bee genome consists of 247 million base pairs. A SNP (single nucleotide polymorphism) is defined as a variation in a single base pair (e.g. the exchange of the base G from AG to AA) and thus describes the smallest possible deviation in the genetic code.
Most SNPs are shared by all honey bee subspecies, meaning they can be found in all populations. However, some SNPs are predominantly or exclusively present in a population, subspecies or breed. Such population-specific SNPs can be used as genetic markers to test the ancestry of a bee.
The genome of the honey bee contains a remarkable number of SNPs (≈ 1 SNP per 300 base pairs). By comparison, the human genome only contains around 1 SNP per 1300 base pairs. That means that the honey bee is an extremely genetically diverse species.
Genetic diversity occurs on different levels: within a colony, within a population and within the entire species. The level of genetic diversity within a population directly affects the diversity within a colony. Numerous scientific studies have shown that high intra-colony genetic diversity is crucial for vitality, thermoregulation, disease resistance and productivity.
In addition, it is also important to maintain the diversity between populations and especially between different subspecies as they possess different adaptation strategies for future environmental changes. High volumes of international transport would facilitate mixing of different subspecies which could lead to the loss of specific properties for local adaptation. A large-scale experiment in 11 European countries with 16 populations could show that locally adapted bees survived longer, had fewer pathogens and were more productive than their introduced conspecifics.
References and further links
Parejo, M., Wragg, D., Gauthier, L., Vignal, A., Neumann, P. & Neuditschko, M. (2016). Using Whole-Genome Sequence Information to Foster Conservation Efforts for the European Dark Honey Bee, Apis mellifera mellifera. Frontiers in Ecology and Evolution, 4, 140. Link
Meixner, M. D., Buchle,r R.,Costa, C., Francis, R.M., Hatjina, F., Kryger, P., Uzunov A. & Carreck, N.L. (2014). Honey bee genotypes and the environment. J. Apic. Res. 53:183-187. Special issue with several articles: Link
Tarpy, D.R., Vanengelsdorp, D. & Pettis, J.S. (2013). Genetic diversity affects colony survivorship in commercial honey bee colonies. Naturwissenschaften 100, 723-728. Link
Desai, S.D. & Currie, R.W. (2015). Genetic diversity within honey bee colonies affects pathogen load and relative virus levels in honey bees, Apis mellifera L. Behavioral Ecology and Sociobiology 69, 1527-1541. Link
Research Network for Sustainable Bee Breeding: Link