Why the bees are also dying: the costs of artificial selection

Jacques van Alphen is emeritus professor of animal ecology. From 1975 to 2011, he worked at Leiden University as a researcher and lecturer. From 2007 tm 2009, he held an EU Chair of Excellence, teaching behavioural ecology at the University of Rennes in France. He has published widely on the behavioural ecology of parasitoids, their application in biological pest control, and on speciation in tropical fish. Now he is affiliated with the Naturalis biodiversity Centre as correspondent.

After retirement he published a review on the role of (natural) selection in honey bee resistance against Varroa mites. He also published a book (in Dutch) on the evolutionary ecology of honey bees.

Modern techniques of selective bee breeding have high potential to improve economically important traits of honey bees. However, this breeding neglects fundamental rules of natural selection. This review explains how resistance alleles have become rare or have disappeared from artificially selected honey bee populations in Europe (and probably also in North America).
Honeybees have the highest recombination frequency of all animals, indicating that pathogenic bacteria, viruses, fungi and microsporidia are an important source of selection. To respond to new virulent strains of pathogens, honeybees need to have access to rare alleles that could foster immunity against a new pathogen.

By mating in a large panmictic population, new rare alleles can be recruited, and combined into new genotypes through recombination with useful alleles of other genes.
Selection for desirable traits typically involves taking a small sample from a larger population. As a result, rare alleles are under sampled and disappear from the selected population with continued artificial selection. In addition, selection for polygenic behavioural traits may result in runs of homozygosity and hampers the role of recombination in the creation of new genotypes. Restoring large panmictic populations of native subspecies of honeybees can provide a reservoir from which lost alleles can be recovered.

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