“Sex is a weird way to reproduce”

• Researchers discover a gene in honey bees that causes virgin birth
• Reversions to asexual reproduction are rare in nature
• This may be the first time that the genetic basis of such a reversion has been discovered
• Mutations of this single gene have changed the reproductive mode of an entire population

**** In a study published today in Current Biology , researchers fromUniversity of Sydney have identified the single gene that determines how Capehoney bees reproduce without ever having sex. One gene, GB45239 on chromosome11, is responsible for virgin births.

“It is extremely exciting,” said Professor Benjamin Oldroyd in theSchool of Life and Environmental Sciences. “Scientists have been lookingfor this gene for the last 30 years. Now that we know it’s on chromosome 11,we have solved a mystery.”

Behavioural geneticist Professor Oldroyd said: “Sex is a weird way toreproduce and yet it is the most common form of reproduction for animals andplants on the planet. It’s a major biological mystery why there is so much sexgoing on and it doesn’t make evolutionary sense. Asexuality is a much moreefficient way to reproduce, and every now and then we see a species revert toit.”

In the Cape honey bee, found in South Africa, the gene has allowed worker beesto lay eggs that only produce females instead of the normal males that otherhoney bees do. “Males are mostly useless,” Professor Oldroyd said. “But Capeworkers can become genetically reincarnated as a female queen and thatprospect changes everything.”

But it also causes problems. “Instead of being a cooperative society, Capehoney bee colonies are riven with conflict because any worker can begenetically reincarnated as the next queen. When a colony loses its queen theworkers fight and compete to be the mother of the next queen,” ProfessorOldroyd said.

The ability to produce daughters asexually, known as “thelytokousparthenogenesis”, is restricted to a single subspecies inhabiting the Caperegion of South Africa, the Cape honey bee or Apis mellifera capensis.

Several other traits distinguish the Cape honey bee from other honey beesubspecies. In particular, the ovaries of worker bees are larger and morereadily activated and they are able to produce queen pheromones, allowing themto assert reproductive dominance in a colony.

These traits also lead to a propensity for social parasitism, a behaviourwhere Cape bee workers invade foreign colonies, reproduce and persuade thehost colony workers to feed their larvae. Every year in South Africa, 10,000colonies of commercial beehives die because of the social parasite behaviourin Cape honey bees.

“This is a bee we must keep out of Australia,” Professor Oldroyd said.

The existence of Cape bees with these characters has been known for over ahundred years, but it is only recently, using modern genomic tools, that wehave been able to understand the actual gene that gives rise to virgin birth.

“Further study of Cape bees could give us insight into two major evolutionarytransitions: the origin of sex and the origin of animal societies,” ProfessorOldroyd said.

Perhaps the most exciting prospect arising from this study is the possibilityto understand how the gene actually works functionally. “If we could control aswitch that allows animals to reproduce asexually, that would have importantapplications in agriculture, biotechnology and many other fields,” ProfessorOldroyd said. For instance, many pest ant species like fire ants arethelytokous, though unfortunately it seems to be a different gene to the onefound in Capensis.”

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