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ABSTRACT
The subspecies of honeybee indigenous to the Cape region of South Africa, Apis mellifera capensis, is unique because a high proportion of unmated workers can lay eggs that develop into females via thelytokous parthenogenesis involving central fusion of meiotic products. This ability allows pseudoclonal lineages of workers to establish, which are presently widespread as reproductive parasites within the honeybee populations of South Africa. Successful long-term propagation of a parthenogen requires the maintenance of heterozygosity at the sex locus, which in honeybees must be heterozygous for the expression of female traits. Thus, in successful lineages of parasitic workers, recombination events are reduced by an order of magnitude relative to meiosis in queens of other honeybee subspecies. Here we show that in unmated A. m. capensis queens treated to induce oviposition, no such reduction in recombination occurs, indicating that thelytoky and reduced recombination are not controlled by the same gene. Our virgin queens were able to lay both arrhenotokous male-producing haploid eggs and thelytokous female-producing diploid eggs at the same time, with evidence that they have some voluntary control over which kind of egg was laid. If so, they are able to influence the kind of second-division meiosis that occurs in their eggs post partum.
IN the honeybee, Apis mellifera, unfertilized eggs normally develop into haploid males by arrhenotokous parthenogenesis. Unfertilized eggs are produced by queens for the production of males and also by unmated queenless workers whose eggs also produce functional males (Dzierzon 1845). Very occasionally, however, a worker will lay an egg in which meiosis II is modified so that an unfertilized egg is able to restore diploidy and become female (Mackensen 1943; Tucker 1958), in a form of parthenogenesis known as thelytoky. Thelytoky is ubiquitous in workers of the South African subspecies A. m. capensis (hereafter Cape) (Onions 1912; Anderson 1963) and is thought to be controlled by a single gene, Th, which a mapping study has suggested may be homologous to Grainy Head of Drosophila melanogaster (Lattorff et al. 2005, 2007). In Cape workers, two haploid pronuclei of second-division meiosis fuse and produce a diploid zygote, which usually gives rise to a female that may be reared as a worker or a queen (Moritz et al. 1996; Jordan et al. 2008)....