Effect of genotype but not of age or caste on olfactory learning performance in the honey bee, Apis mellifera

The ability to change expression of a behaviour through experience with contingencies among important stimuli can enhance the survival and fitness of animals under certain ecological conditions. It would seem paradoxical if strong variability in learning performance persists even when those conditions are met. In the honey bee, learning about the relationship between floral odours and the rewards offered by flowers is important for colony survival. Yet several studies have identified a significant amount of inter-individual variability in olfactory learning performance among workers within colonies. This variability could be due to changes in learning performance due to age, to caste-specific alteration of motivational state, or to genotypic variability among paternal lines within colonies. Experiments reported herein were designed to establish the contribution of all three variables under controlled environmental conditions within which significant variability in a measure of learning performance exists. The results indicate that, at least under these conditions and when genotype is not manipulated, neither age nor caste had an effect on motivational state or learning performance. Genotype was the only variable that could account for a substantial portion of the variability within colonies of honey bees. Therefore, manipulation of genotype will be necessary in future studies designed to establish the reasons underlying variability in learning performance in natural populations.