Conservation of Honeybee (Apis mellifera) Intraspecific Diversity Through Reproductive Science and Technology

There are approximately 30 subspecies of the Western honeybee (Apis mellifera), many of which are threatened by genetic introgression due to migratory beekeeping as well an intensive trade with queens and colonies. Invasive pests and parasites can additionally lead to the loss of wild and feral populations. Because A. mellifera mates in free flight and in central "congregation areas", gene flow between managed and unmanaged populations is extremely hard to prevent. Therefore, conservation through utilization is generally viewed as the most promising (though not the only) way to preserve intraspecific biodiversity, and the development and spread of techniques for mating control are critical for maintaining indigenous populations and breed apiculturally acceptable stock from them. The oldest and still the most widespread method of mating control is the use of geographically isolated "Mating stations". Its use is limited due to the lack of suitable locations and the organizational burden it involves. Artificial insemination of honeybee bee queens has been possible since the 1920s and is increasingly used for conservational breeding to control inbreeding in small remnant populations. Variants such as single drone insemination or insemination with homogenized semen are widely used to fasten trait-based breeding, e.g. to increase parasite resistance. A third method of mating control is the "delayed flight-time method", based on temporal isolation of mating flights. Interest in this technique has grown in recent years due to technical simplifications. These techniques of in situ conservation are complemented by protocols for ex situ storage of honeybee semen, leading to the creation of cryobanks on several continents since 2010. Cryostorage of honeybee embryos is still not practically feasible but is presently the object of intensive research. Preservation of A. mellifera diversity relies on classical morphometrical methods to tell apart subspecies and ecotypes, recently complemented by SNP panels for taxonomic diagnosis, analysis of relatedness, and introgression. Methods of quantitative genetics such as REML have been adapted to the biological peculiarities of the species and can be combined with molecular tools to control inbreeding.Climate change is leading to sometimes drastic changes in the availability of pollen and nectar. Together with international trade, it is also allowing the spread of honeybee parasites and predators. While these factors may increase the vulnerability of endemic honeybee populations, there is also hope that they may lead to their increased appreciation by beekeepers, who are recognizing them as important reservoirs of preadaptations, given evidence that locally adapted genotypes are often more resilient towards new stressors. The challenge will lie in preserving the genetic identity of diverse A. mellifera populations while allowing them to further adapt to environmental change and also to the needs of beekeepers, in whose hands their survival will often lie. Improvement and generalized access to reproductive technologies such as mating control, ex situ storage of germplasm, and molecular tools to manage diversity will doubtlessly be crucial for the success of this process.