How does a swarm of the giant Asian honeybee Apis dorsata reach consensus? A study of the individual behaviour of scout bees

The last few years have seen a renewed interest in the mechanisms behind nest-site selection in honeybees. Most studies have focused on the cavity-nesting honeybee Apis mellifera, but more recently studies have included the open-nesting A. florea. Amongst species comparisons are important if we want to understand how the process has been adapted over evolutionary time to suit the particular species’ nest-site requirement. Here, we describe the behaviour of scout bees of the giant Asian honeybee A. dorsata on three artificially created swarms to determine the mechanisms used to collectively decide on a location to move to, either in the same environment (nest-site selection) or somewhere further afield (migration). In all swarms, scouts’ dances converged on a general direction prior to lift-off and this direction corresponded to the direction that swarms flew. Scouts from one swarm danced for sites that were far away. These dances did not converge onto a specific distance, implying they were migration dances. Dances for different sites differed in the number of circuits per dance suggesting that A. dorsata scouts make an assessment of site quality. Similarly to A. florea, but in contrast to A. mellifera, A. dorsata scouts did not reduce dance duration after repeated returns from scouting flights. We found that many scouts that dance for a non-preferred location changed dance location during the decision-making process after following dances for the consensus direction. We conclude that the consensus building process of A. dorsata swarms relies on the interaction of scout bees on the swarm

Two extended haplotype blocks are associated with adaptation to high altitude habitats in East African honey bees

Understanding the genetic basis of adaption is a central task in biology. Populations of the honey bee Apis mellifera that inhabit the mountain forests of East Africa differ in behavior and morphology from those inhabiting the surrounding lowland savannahs, which likely reflects adaptation to these habitats. We performed whole genome sequencing on 39 samples of highland and lowland bees from two pairs of populations to determine their evolutionary affinities and identify the genetic basis of these putative adaptations. We find that in general, levels of genetic differentiation between highland and lowland populations are very low, consistent with them being a single panmictic population. However, we identify two loci on chromosomes 7 and 9, each several hundred kilobases in length, which exhibit near fixation for different haplotypes between highland and lowland populations. The highland haplotypes at these loci are extremely rare in samples from the rest of the world. Patterns of segregation of genetic variants suggest that recombination between haplotypes at each locus is suppressed, indicating that they comprise independent structural variants. The haplotype on chromosome 7 harbors nearly all octopamine receptor genes in the honey bee genome. These have a role in learning and foraging behavior in honey bees and are strong candidates for adaptation to highland habitats. Molecular analysis of a putative breakpoint indicates that it may disrupt the coding sequence of one of these genes. Divergence between the highland and lowland haplotypes at both loci is extremely high suggesting that they are ancient balanced polymorphisms that greatly predate divergence between the extant honey bee subspecies