While workers of almost all subspecies of honeybee are able to lay only haploid male eggs, Apis mellifera capensis workers are able to produce diploid female eggs by thelytokous parthenogenesis. Cytological analyses have shown that during parthenogenesis, egg diploidy is restored by fusion of the two central meiotic products. This peculiarity of the Cape bee preserves two products of a single meiosis in the daughters and can be used to map centromere positions using half-tetrad analysis. In this study, we use the thelytokous progenies of A. m. capensis workers and a sample of individuals from a naturally occurring A. m. capensis thelytokous clone to map centromere position for most of the linkage groups of the honeybee. We also show that the recombination rate is reduced by Ͼ10-fold during the meiosis of A. m. capensis workers. This reduction is restricted to thelytokous parthenogenesis of capensis workers and is not observed in the meiosis of queen within the same subspecies or in arrhenotokous workers of another subspecies. The reduced rate of recombination seems to be associated with negative crossover interference. These results are discussed in relation to evolution of thelytokous parthenogenesis and maintenance of heterozygosity and female sex after thelytoky.

The honeybee (Apis mellifera) queen mates during nuptial £ights, in the so-called drone congregation area where many males from surrounding colonies gather. Using 20 highly polymorphic microsatellite loci, we studied a sample of 142 drones captured in a congregation close to Oberursel (Germany). A parentage test based on lod score showed that this sample contained one group of four brothers, six groups of three brothers, 20 groups of two brothers and 80 singletons. These values are very close to a Poisson distribution. Therefore, colonies were apparently equally represented in the drone congregation, and calculations showed that the congregation comprised males that originated from about 240 di¡erent colonies. This ¢gure is surprisingly high. Considering the density of colonies around the congregation area and the average £ight range of males, it suggests that most colonies within the recruitment perimeter delegated drones to the congregation with an equal probability, resulting in an almost perfect panmixis. Consequently, the relatedness between a queen and her mates, and hence the inbreeding coe¤cient of the progeny, should be minimized. The relatedness among the drones mated to the same queen is also very low, maximizing the genetic diversity among the di¡erent patrilines of a colony.

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.

SummaryPollination by honey bees plays a key role in the functioning of ecosystems and optimisation of agricultural yields. Severe honey bee colony losses worldwide have raised concerns about the sustainability of these pollination services. In many cases, bee mortality appears to be the product of many interacting factors, but there is a growing consensus that the ectoparasitic mite Varroa destructor plays the role of the major predisposing liability. We argue that the fight against this mite should be a priority for future honey bee health research. We highlight the lack of efficient control methods currently available against the parasite and discuss the need for new approaches. Gaps in our knowledge of the biology and epidemiology of the mite are identified and a research road map towards sustainable control is drawn. Innovative and challenging approaches are suggested in order to stimulate research efforts and ensure that honey bees will be able to sustainably fulfil their role in the ecosystem. Varroa destructor: alternativas para su control sostenible ResumenLa polinización por las abejas melíferas tiene una importante relevancia en el funcionamiento de los ecosistemas y en la optimización de los rendimientos agrícolas. Se ha expresado la preocupación acerca de la sostenibilidad de estos servicios de polinización, debido a las graves pérdidas de colonias de abejas melíferas a nivel mundial. En varios de estos casos, la pérdida de estas abejas parece ser el resultado de la interacción de muchos factores, existiendo un creciente consenso en que el ácaro ectoparásito Varroa destructor desempeña alguna

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