Abstract
Simple SummaryThis study is the first to compare the associative learning performance of six honeybee subspecies from different European regions in a common apiary. We quantified sucrose responsiveness prior to appetitive olfactory proboscis extension learning to dissociate effects of motivation and cognition. Our results show that Apis mellifera iberiensis displayed a significantly poorer learning performance compared to other Apis subspecies from across Europe, which did not differ from each other. Possible causes are discussed.The Western honeybee (Apis mellifera L.) is one of the most widespread insects with numerous subspecies in its native range. How far adaptation to local habitats has affected the cognitive skills of the different subspecies is an intriguing question that we investigate in this study. Naturally mated queens of the following five subspecies from different parts of Europe were transferred to Southern Germany: A. m. iberiensis from Portugal, A. m. mellifera from Belgium, A. m. macedonica from Greece, A. m. ligustica from Italy, and A. m. ruttneri from Malta. We also included the local subspecies A. m. carnica in our study. New colonies were built up in a common apiary where the respective queens were introduced. Worker offspring from the different subspecies were compared in classical olfactory learning performance using the proboscis extension response. Prior to conditioning, we measured individual sucrose responsiveness to investigate whether possible differences in learning performances were due to differential responsiveness to the sugar water reward. Most subspecies did not differ in their appetitive learning performance. However, foragers of the Iberian honeybee, A. m. iberiensis, performed significantly more poorly, despite having a similar sucrose responsiveness. We discuss possible causes for the poor performance of the Iberian honeybees, which may have been shaped by adaptation to the local habitat.
Highlights
We aimed to investigate whether the correlation between individual sucrose responsiveness and appetitive learning performance described for A. m. carnica and A. m. ligustica is present in the other subspecies, pointing towards a general rule for appetitive associative learning
The bees tested for their appetitive olfactory learning performance were all highly motivated, i.e., displaying a high sucrose responsiveness, which is an indicator of their “learning motivation” and can predict learning performance to a high degree [19,24,27,38]
A. m. ligustica [19,23] were present in the other honeybee subspecies, there should be few differences in the learning performance of the different subspecies, since the majority of differences in appetitive olfactory learning can be attributed to differences in the sucrose responsiveness of the bees [27]
Summary
The intraspecific diversity of Apis mellifera is remarkable, with currently about 30 subspecies described [1,7,8,9,10]. The different subspecies display diverse adaptations to a wide variety of geographic areas and environmental factors. They can be grouped into five evolutionary lineages (A, M, C, O, and Y), based on morphometric and molecular studies [7,8,9,11]. Whereas the subspecies of lineage A are spread across Africa, those belonging to lineage Y originate in North-Eastern Africa. Subspecies of lineage M are distributed widely in Western and Northern Europe, while lineage C comprises subspecies originating from South-Eastern
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