Reversions to virgin births by asexual reproduction are rare in nature. Asexual birth, in Cape honey bees, might be the first time that the genetic basis of such a phenomenon has been discovered. In a study published in Current Biology, researchers from the University of Sydney have identified the single gene that determines how Cape honey bees reproduce without ever having sex. One gene, GB45239 on chromosome 11, is responsible for virgin births.
Cape honey bee workers laying parasitic eggs on a queen cell. (Image: via Benjamin Oldroyd)
Professor Benjamin Oldroyd, from the School of Life and Environmental Sciences, said in a statement:
“It is extremely exciting, scientists have been looking for this gene for the last 30 years. Now that we know it’s on chromosome 11, we have solved a mystery.”
Behavioral geneticist Professor Oldroyd said:
“Sex is a weird way to reproduce and yet it is the most common form of reproduction for animals and plants on the planet. It’s a major biological mystery why there is so much sex going on and it doesn’t make evolutionary sense. Asexuality is a much more efficient way to reproduce, and every now and then we see a species revert to it.”
Masses of parasitic eggs laid by parasites in a dying colony. (Image: via Benjamin Oldroyd)
Cape honey bees lay eggs that only produce females
In the Cape honey bee, found in South Africa, the gene has allowed worker bees to lay eggs that only produce females instead of the normal males that other honey bees do. Professor Oldroyd added:
“Males are mostly useless. but Cape workers can become genetically reincarnated as a female queen and that prospect changes everything.”
But it also causes problems, according to Professor Oldroyd:
“Instead of being a cooperative society, Cape honey bee colonies are riven with conflict because any worker can be genetically reincarnated as the next queen. When a colony loses its queen the workers fight and compete to be the mother of the next queen.”
Only the Cape honey bee has virgin births
The ability to produce daughters asexually through virgin births, known as “thelytokous parthenogenesis,” is restricted to a single subspecies inhabiting the Cape region of South Africa, the Cape honey bee, or Apis mellifera capensis. Several other traits distinguish the Cape honey bee from other honey bee subspecies. In particular, the ovaries of worker bees are larger and more readily activated, and they can produce queen pheromones, allowing them to assert reproductive dominance in a colony.
The sexual Cape honey bee queen surrounded by her asexual workers. (Image: via Benjamin Oldroyd)
These traits also lead to a propensity for social parasitism, a behavior where Cape bee workers invade foreign colonies, reproduce, and persuade the host colony workers to feed their larvae. Every year in South Africa, 10,000 colonies of commercial beehives die because of the social parasitic behavior of Cape honey bees. Professor Oldroyd said:
“This is a bee we must keep out of Australia.”
The existence of Cape bees with these characters has been known for over a hundred years, but it is only recently, using modern genomic tools, that we have been able to understand the actual gene that gives rise to these virgin births, according to Professor Oldroyd He says:
“Further study of Cape bees could give us insight into two major evolutionary transitions: the origin of sex and the origin of animal societies.”
Perhaps the most exciting prospect arising from this study is the possibility of understanding how the gene works functionally. Professor Oldroyd concluded by saying:
“If we could control a switch that allows animals to reproduce asexually, that would have important applications in agriculture, biotechnology and many other fields. For instance, many pest ant species like fire ants are thelytokous, though unfortunately it seems to be a different gene to the one found in Capensis.”
Provided by: University of Sydney [Note: Materials may be edited for content and length.]
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