Testing genetic variance hypotheses for the evolution of polyandry in the honeybee (Apis mellifera L.)

Abstract

Colony size, honey yields and colony levels of infestation with Varroa jacobsoni of 30 queenright honeybee (Apis mellifera) colonies with naturally mated queens were evaluated over a two-year period. Workers taken from each colony were genotyped at four DNA-microsatellite loci to determine the level of polyandry. All queens mated with more than 10 drones (mean number of observed patrilines = 17.7 ± 5.23). We found significant correlations between colony size and honey yield and between colony sizes of two subsequent years. Analyses of variance revealed a strong impact of the breeding lines on the tested phenotypic traits. The impact of polyandry on colony honey yields was weak (p < 0.05, not significant when applying a Bonferroni adjustment) and 8% of the phenotype was determined by the effect of polyandry. The contribution of polyandry to colony size (0.25%) or levels of infestation with Varroa jacobsoni (0.09%) was even weaker in both test years. Likewise, we could not find any averaging effect of polyandry on the honey yield, size nor parasite load of honeybee colonies. Our data set does not resolve the question, whether polyandry and genetic diversity causes more productive colonial phenotypes. If colony level selection is an evolutionary force for polyandry, the effects are hard to detect in man-kept colonies headed by naturally mated queens.