A single gene allows Cape honey bees to reproduce asexually

A team of scientists has solved the mystery of how honey bees in the Cape region of South Africa are capable of virgin births. Researchers at the University of Sydney have discovered that a single gene makes it possible for Cape honey bees to reproduce without ever having sex.

“It is extremely exciting,” said Professor Benjamin Oldroyd. “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.”

“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.”

A gene found on chromosome 11, GB45239, allows the Cape honey worker bees to lay eggs that produce only females. 

“Males are mostly useless,” said Professor Oldroyd. “But Cape workers can become genetically reincarnated as a female queen and that prospect changes everything.”

The Cape bees make up the only known subspecies of honey bees with the ability to produce daughters asexually, known as “thelytokous parthenogenesis.” Despite the benefits of having an abundance of worker bees, this also causes conflict. 

“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,” explained Professor Oldroyd. “When a colony loses its queen the workers fight and compete to be the mother of the next queen.”

The Cape honey bees have other unique characteristics beyond asexual reproduction. The ovaries of the female bees are larger, more easily activated, and are able to produce queen pheromones. These chemicals trigger a social response from other honey bees, including those in foreign colonies.  

The Cape bees often use queen pheromones for social parasitism, which is when they invade foreign colonies and assert reproductive dominance. Each year, about 10,000 colonies of commercial beehives are lost in South Africa due to the social parasitic behavior of Cape honey bees.

While it has been known for a century that Cape bees are capable of virgin births, a modern genomic tool was needed to pinpoint the genetic mechanism that is involved. 

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

For the researchers, one of the most exciting prospects is the potential to understand how the newly-identified gene actually works. 

“If we could control a switch that allows animals to reproduce asexually, that would have important applications in agriculture, biotechnology and many other fields,” said Professor Oldroyd.

The study is published in the journal Current Biology.

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By Chrissy Sexton, Earth.com Staff Writer