Amro Zayed

Adaptive, caste-specific changes to recombination rates in a thelytokous honeybee population

Publisher: The Royal Society

Date: 09-06-2021

DOI: 10.1098/RSPB.2021.0729

Abstract: The ability to clone oneself has clear benefits—no need for mate hunting or dilution of one's genome in offspring. It is therefore unsurprising that some populations of haplo-diploid social insects have evolved thelytokous parthenogenesis—the virgin birth of a female. But thelytokous parthenogenesis has a downside: the loss of heterozygosity (LoH) as a consequence of genetic recombination. LoH in haplo-diploid insects can be highly deleterious because female sex determination often relies on heterozygosity at sex-determining loci. The two female castes of the Cape honeybee, Apis mellifera capensis , differ in their mode of reproduction. While workers always reproduce thelytokously, queens always mate and reproduce sexually. For workers, it is important to reduce the frequency of recombination so as to not produce offspring that are homozygous. Here, we ask whether recombination rates differ between Cape workers and Cape queens that we experimentally manipulated to reproduce thelytokously. We tested our hypothesis that Cape workers have evolved mechanisms that restrain genetic recombination, whereas queens have no need for such mechanisms because they reproduce sexually. Using a combination of microsatellite genotyping and whole-genome sequencing we find that a reduction in recombination is confined to workers only.

Strikingly high levels of heterozygosity despite 20 years of inbreeding in a clonal honey bee

Publisher: Wiley

Date: 07-12-2019

DOI: 10.1111/JEB.13397

Abstract: Inbreeding (the mating between closely related in iduals) often has detrimental effects that are associated with loss of heterozygosity at overdominant loci, and the expression of deleterious recessive alleles. However, determining which loci are detrimental when homozygous, and the extent of their phenotypic effects, remains poorly understood. Here, we utilize a unique inbred population of clonal (thelytokous) honey bees, Apis mellifera capensis, to determine which loci reduce in idual fitness when homozygous. This asexual population arose from a single worker ancestor approximately 20 years ago and has persisted for at least 100 generations. Thelytokous parthenogenesis results in a 1/3 of loss of heterozygosity with each generation. Yet, this population retains heterozygosity throughout its genome due to selection against homozygotes. Deep sequencing of one bee from each of the three known sub-lineages of the population revealed that 3,766 of 10,884 genes (34%) have retained heterozygosity across all sub-lineages, suggesting that these genes have heterozygote advantage. The maintenance of heterozygosity in the same genes and genomic regions in all three sub-lineages suggests that nearly every chromosome carries genes that show sufficient heterozygote advantage to be selectively detrimental when homozygous.

Genetic origins of honey bees (Apis mellifera) on Kangaroo Island and Norfolk Island (Australia) and the Kingdom of Tonga

Publisher: Springer Science and Business Media LLC

Date: 07-01-2019

DOI: 10.1007/S13592-018-0615-X

University Of Illinois Urbana-Champaign

Location: United States of America

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York University

Location: Canada

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Discovery Projects - Grant ID: DP180101696

Start Date: 2018

End Date: 12-2020

Amount: $289,844.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP190101500

Start Date: 2019

End Date: 06-2022

Amount: $321,000.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP210101084

Start Date: 12-2021

End Date: 01-2022

Amount: $288,760.00

Funder: Australian Research Council