Cytogenetic basis of thelytoky in Apis mellifera capensis (original) (raw)
Related papers
Genetics, 2004
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.
Thelytoky in Cape honeybees (Apis mellifera capensis ) is controlled by a single recessive locus
– Worker reproduction in Apis mellifera typically leads to haploid males produced via arrhenotokous parthenogenesis. An exception are laying workers of the South African Cape honeybee Apis mellifera capensis. Due to an abnormal spindle rotation during meiosis A. m. capensis workers are able to produce female progeny via thelytokous parthenogenesis. This trait has been suggested to be genetically controlled by a recessive allele at the thelytoky locus (th), but this conclusion was recently challenged by Chapman et al. (2015). To clarify the mode of inheritance for thelytokous parthenogenesis in Cape honeybees, we determined the sex of the offspring of 74 A. m. capensis workers of a single queen from a colony of the endemic wild population at the Cape of Good Hope Nature Reserve. When we tested individual worker reproduction, parthenogenesis was dimorphic, segregating in a Mendelian fashion supporting the single locus model. We could exclude maternal or paternal effects determining the mode of parthenogenesis. A careful re-analysis of the data of Chapman et al. (2015) also revealed that their data do not contradict the one locus model for the inheritance of thelytoky. thelytoky / worker reproduction / reproductive dominance / asexual reproduction / gemini
Heredity, 2004
The evolution and maintenance of parthenogenetic species are a puzzling issue in evolutionary biology. Although the genetic mechanisms that act to restore diploidy are well studied, the underlying genes that cause the switch from sexual reproduction to parthenogenesis have not been analysed. There are several species that are polymorphic for sexual and parthenogenetic reproduction, which may have a genetic basis. We use the South African honeybee subspecies Apis mellifera capensis to analyse the genetic control of thelytoky (asexual production of female workers). Due to the caste system of honeybees, it is possible to establish classical backcrosses using sexually reproducing queens and drones of both arrhenotokous and thelytokous subspecies, and to score the frequency of parthenogenesis in the resulting workers. We found Mendelian segregation for thelytoky of egg-laying workers, which appears to be controlled by a single major gene (th). The segregation pattern indicates a recessive allele causing thelytoky. We found no evidence for maternal transmission of bacterial endosymbionts controlling parthenogenesis. Thelytokous parthenogenesis of honeybee workers appears to be a classical qualitative trait, because we did not observe mixed parthenogenesis (amphitoky), which might be expected in the case of multi-locus inheritance. Heredity (2005) 94, 533-537.
Reproductive biology of the Cape honeybee: A critique of Beekman et al.
Journal of Heredity, 2012
A critique of ''Asexually Produced Cape Honeybee Queens (Apis mellifera capensis) Reproduce Sexually'': Laying workers of the Cape honeybee parthenogenetically produce female offspring, whereas queens typically produce males. Beekman et al. confirm this observation, which has repeatedly been reported over the last 100 years including the notion that natural selection should favor asexual reproduction in Apis mellifera capensis. They attempt to support their arguments with an exceptionally surprising finding that A. m. capensis queens can parthenogenetically produce diploid homozygous queen offspring (homozygous diploid individuals develop into diploid males in the honeybee). Beekman et al. suggest that these homozygous queens are not viable because they did not find any homozygous individuals beyond the third larval instar. Even if this were true, such a lethal trait should be quickly eliminated by natural selection. The identification of sex (both with molecular and morphological markers) is possible but notoriously difficult in honeybees at the early larval stages. Ploidy is however a reliable indicator, and we therefore suggest that these ''homozygous'' larvae found in queen cells are actually drones reared from unfertilized eggs, a phenomenon well known by honeybee queen breeders.
Unusually high recombination rate detected in the sex locus region of the honey bee (Apis mellifera)
Genetics, 1999
Sex determination in Hymenoptera is controlled by haplo-diploidy in which unfertilized eggs develop into fertile haploid males. A single sex determination locus with several complementary alleles was proposed for Hymenoptera [so-called complementary sex determination (CSD)]. Heterozygotes at the sex determination locus are normal, fertile females, whereas diploid zygotes that are homozygous develop into sterile males. This results in a strong heterozygote advantage, and the sex locus exhibits extreme polymorphism maintained by overdominant selection. We characterized the sex-determining region by genetic linkage and physical mapping analyses. Detailed linkage and physical mapping studies showed that the recombination rate is <44 kb/cM in the sex-determining region. Comparing genetic map distance along the linkage group III in three crosses revealed a large marker gap in the sex-determining region, suggesting that the recombination rate is high. We suggest that a "hotspot&quo...
Journal of Heredity, 2012
A critique of ''Asexually Produced Cape Honeybee Queens (Apis mellifera capensis) Reproduce Sexually'': Laying workers of the Cape honeybee parthenogenetically produce female offspring, whereas queens typically produce males. Beekman et al. confirm this observation, which has repeatedly been reported over the last 100 years including the notion that natural selection should favor asexual reproduction in Apis mellifera capensis. They attempt to support their arguments with an exceptionally surprising finding that A. m. capensis queens can parthenogenetically produce diploid homozygous queen offspring (homozygous diploid individuals develop into diploid males in the honeybee). Beekman et al. suggest that these homozygous queens are not viable because they did not find any homozygous individuals beyond the third larval instar. Even if this were true, such a lethal trait should be quickly eliminated by natural selection. The identification of sex (both with molecular and morphological markers) is possible but notoriously difficult in honeybees at the early larval stages. Ploidy is however a reliable indicator, and we therefore suggest that these ''homozygous'' larvae found in queen cells are actually drones reared from unfertilized eggs, a phenomenon well known by honeybee queen breeders.
What mechanistic factors affect thelytokous parthenogenesis in Apis mellifera caponises queens?
Apidologie, 2020
The Cape honey bee (Capensis) is unusual in that workers can produce viable female offspring via thelytokous parthenogenesis. In contrast, mated queens never reproduce thelytokously, even though they could benefit from doing so when generating daughter queens. Nonetheless, virgin Capensis queens induced to lay without mating by CO 2 narcosis produce a high proportion of thelytokous eggs, and instrumentally inseminated queens produce triploid offspring as the result of the fusion of two egg pronuclei and a sperm nucleus. We show here that thelytoky/triploidy in Capensis queens is not a consequence of CO 2 narcosis per se because narcosis of laying queens does not induce thelytokous or triploid progeny. We also show that in artificially inseminated queens, the frequency of thelytoky/triploidy declines with age and is absent 10 months post-insemination. We confirm that the presence of semen in the spermatheca is not the mechanism that prevents thelytoky/triploidy in mated queens.
Journal of Evolutionary Biology, 2011
Determining the extent and causes of barriers to gene flow is essential for understanding sympatric speciation, but the practical difficulties of quantifying reproductive isolation remain an obstacle to analysing this process. Social parasites are common in eusocial insects and tend to be close phylogenetic relatives of their hosts (= Emery's rule). Sympatric speciation caused by reproductive isolation between host and parasite is a possible evolutionary pathway. Socially parasitic workers of the Cape honeybee, Apis mellifera capensis, produce female clonal offspring parthenogenetically and invade colonies of the neighbouring subspecies A. m. scutellata. In the host colony, socially parasitic workers can become pseudoqueens, an intermediate caste with queenlike pheromone secretion. Here, we show that over an area of approximately 275.000 km 2 , all parasitic workers bear the genetic signature of a clone founded by a single ancestral worker genotype. Any gene flow from the host to the parasite is impossible because honeybee workers cannot mate. Gene flow from the parasite to the host is possible, as parasitic larvae can develop into queens. However, we show that despite sympatric coexistence for more than a decade, gene flow between host and social parasite (F st = 0.32) and hybridizations (0.71%) are rare, resulting in reproductive isolation. Our data suggest a new barrier to gene flow in sympatry, which is not based on assortative matings but on thelytoky and reproductive division of labour in eusocial insects, thereby suggesting a new potential pathway to Emery's rule.
Evidence of separate karyotype evolutionary pathway in Euglossa orchid bees by cytogenetic analyses
Euglossini are solitary bees considered important pollinators of many orchid species. Information regarding chromosome organization is available for only a small number of species in this group. In the present work, the species Euglossa townsendi and E. carolina were analyzed by cytogenetic techniques to collect information that may aid the understanding of their evolution and chromosomal organization. The chromosome number found was n = 21 for males and 2n = 42 for females in the two species. The distribution and amount of heterochromatin regions differed in the two species analyzed, where they were classified as "high" or "low" heterochromatin content, similarly to what has already been performed in social bee species of the genus Melipona. Banding patterns found in this study suggest that other mechanisms may have occurred in the karyotype evolution of this group, unlike those suggested for social bees and ants. Karyotype evolution of solitary bees appears to have occurred as an event separate from other hymenopterans and did not involve chromosome fissions and heterochromatin amplification.