Intracolonial genetic variability in honeybee larval resistance to the chalkbrood and American foulbrood parasites

The origin of multiple mating of queens in social Hymenoptera is a widely debated topic in evolutionary biology. One of the hypotheses is that genetic variability would benefit the colony by increasing its resistance to parasites through various mechanisms. One among the predictions of this hypothesis is that the resistance of different patrilines within a colony to parasites of different species should be independent, as a result of independent gene-for-gene interactions with each parasite. To test this aspect of the hypothesis, two honeybee colonies (Apis mellifera) were infected with the fungus Ascosphaera apis and two colonies with both A. apis and the American foulbrood bacterium Paenibacillus larvae. Patrilines were found to vary in resistance of larvae to A. apis in all four colonies, but similar variation in resistance was not found to P. larvae. Common resistance to both pathogens was not detected. This study supports the hypothesis that polyandry in social insects could have originated as an adaptation to decrease the impact of diseases.