Our understanding of the impact of recombination, mutation, genetic drift, and selection on the evolution of a single gene is still limited. Here we investigate the impact of all these evolutionary forces at the complementary sex determiner (csd) gene that evolves under a balancing mode of selection. Females are heterozygous at the csd gene and males are hemizygous; diploid males are lethal and occur when csd is homozygous. Rare alleles thus have a selective advantage, are seldom lost by the effect of genetic drift, and are maintained over extended periods of time when compared with neutral polymorphisms. Here, we report on the analysis of 17, 19, and 15 csd alleles of Apis cerana, Apis dorsata, and Apis mellifera honeybees, respectively. We observed great heterogeneity of synonymous (piS) and nonsynonymous (piN) polymorphisms across the gene, with a consistent peak in exons 6 and 7. We propose that exons 6 and 7 encode the potential specifying domain (csd-PSD) that has accumulated elevated nucleotide polymorphisms over time by balancing selection. We observed no direct evidence that balancing selection favors the accumulation of nonsynonymous changes at csd-PSD (piN/piS ratios are all <1, ranging from 0.6 to 0.95). We observed an excess of shared nonsynonymous changes, which suggest that strong evolutionary constraints are operating at csd-PSD resulting in the independent accumulation of the same nonsynonymous changes in different alleles across species (convergent evolution). Analysis of csd-PSD genealogy revealed relatively short average coalescence times ( approximately 6 Myr), low average synonymous nucleotide diversity (piS < 0.09), and a lack of trans-specific alleles that substantially contrasts with previously analyzed loci under strong balancing selection. We excluded the possibility of a burst of diversification after population bottlenecking and intragenic recombination as explanatory factors, leaving high turnover rates as the explanation for this observation. By comparing observed allele richness and average coalescence times with a simplified model of csd-coalescence, we found that small long-term population sizes (i.e., N(e) < 10(4)), but not high mutation rates, can explain short maintenance times, implicating a strong historical impact of genetic drift on the molecular evolution of highly social honeybees.

SummaryIn this BEEBOOK paper we present a set of established methods for quantifying honey bee behaviour. We start with general methods for preparing bees for behavioural assays. Then we introduce assays for quantifying sensory responsiveness to gustatory, visual and olfactory stimuli. Presentation of more complex behaviours like appetitive and aversive learning under controlled laboratory conditions and learning paradigms under free-flying conditions will allow the reader to investigate a large range of cognitive skills in honey bees. Honey bees are very sensitive to changing temperatures. We therefore present experiments which aim at analysing honey bee locomotion in temperature gradients. The complex flight behaviour of honey bees can be investigated under controlled conditions in the laboratory or with sophisticated technologies like harmonic radar or RFID in the field. These methods will be explained in detail in different sections. Honey bees are model organisms in behavioural biology for their complex yet plastic division of labour. To observe the daily behaviour of individual bees in a colony, classical observation hives are very useful. The setting up and use of typical observation hives will be the focus of another section. The honey bee dance language has important characteristics of a real language and has been the focus of numerous studies. We here discuss the background of the honey bee dance language and describe how it can be studied. Finally, the mating of a honey bee queen with drones is

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Summary — We compared drones of different body size. Small drones were reared in worker cells while large drones originated from drone cells. We used the cordovan (cd) mutant as a marker. The distribution of drone types in a drone congregation area was monitored by pheromone traps. No significant differences in temporal, horizontal and vertical distributions of large (cd) drones were found, either in comparison with large (+) or in the experiment with small (+) drones. The offspring of homozygous cordovan (cd/cd) queens which were mated during the experiment by (cd) and (+) drones was examined. We compared the ratio of (cd/cd) and (cd/+) workers to the drone ratio at time of the mating flight. Small drones had a reproductive disadvantage compared with large drones. Large (cd) drones had a lower reproductive success compared to large (+) drones.

-In Apis mellifera the estimated average number of drones visiting a drone congregation area (DCA) was 11 750 + 2 145. Drones of the species Apis cerana, A. koschevnikovi, A. dorsata and A. mellifera, which pursued a queen dummy moving in circular course, flew in a comet shaped formation. Median numbers of drones in a comet ranged from 9 drones (A. koschevnikovi) to 31 drones (A. mellifera).In none of the species we observed aggression between drones. Drone density behind the queen and distance to the queen seemed to be adjusted to avoid collisions between drones. The median flight speed ranged from 2.6 m/s (A. koschevnikovi) to 4.1 m/s (A. dorsata). The median duration of a drone's presence in the mating comet did not exceed 2 seconds. Drones of all species had the ability of high acceleration (10 to 20 m/s 2 ). Either by overtaking or leaving/entering the comet drones seem to compete for more promising positions. Only drones flying in a limited space of not more than 2000 cm 3 behind the queen were successful in grasping the dummy.Apis reproduction / mating behavior / drone congregation area / drone competition / drone numbers

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