The Downside of Selection: A Forgotten Cause of Honeybee Decline

Author(s): Jacques JM van Alphen

This article explains how resistance alleles have disappeared from honeybee populations in Europe and North America. Honeybees have the highest recombination frequency of any animal, suggesting that pathogenic bacteria, viruses, fungi and microsporidia are an important source of selection. To respond to new virulent strains of pathogens, honeybees need access to rare alleles that could confer immunity to a new pathogen. By mating in a large panmictic population, new rare alleles can be recruited, which can then be 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 as selection continues. In addition, selection for polygenic behavioural traits leads to runs of homozygosity and hampers the role of recombination in creating 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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