A sci-fi-like phenomenon has been quietly taking place for three decades, going relatively unnoticed for a very long time.
There is an unseen threat in the hives of African lowland honeybees (Apis mellifera scutella) that is causing their colonies to collapse. The enemy is a growing clone army of a rival bee subspecies that appears to have immortal genes.
South African Cape honeybees (Apis mellifera capensis) are a subspecies of the western honeybee. They invade the hives of the African lowland honeybees and the female worker bees of this rival subspecies clone themselves perfectly.
It has been discovered that one worker bee did this thirty years ago, and it has been done millions of times since by her descendants. They have no need for a queen. They sneak inside the hives of their rival, the African lowland honeybee, and their perpetual cloning ability allows South African Cape honeybees to churn out endless replicas. The freeloader clones refuse to work, expecting the host bees to do everything.
This 3:13-minute video by Varun Goad gives some interesting perspective to this story:
A new study sheds light on the genetic basis of this bizarre adaptation. These female worker bees are unlike their own queens and most other animals. They do not rearrange the DNA of the eggs they lay, causing these worker bees to recreate perfect clones of themselves. Researchers have never seen such bypassing of the DNA-reshuffling process.
Thelytokous Parthenogenesis is the definition of asexual reproduction that honeybee workers and other social insects utilize, where females produce female offspring from unfertilized eggs. The single-parent worker bee clones her own chromosomes which she received from her own parents, a queen bee and male drone, into four.
But she doesn’t stop there. She takes this genetic material from all four chromosomes, and rearranges it, which produces four chromosomes with mixed-up or reshuffled DNA. This process is known as recombination. This ensures that future offspring will be genetically altered, even with just the one parent involved.
Benjamin Oldroyd is a professor of behavioral genetics at the University of Sydney and is the lead author. He told Live Science that it is incredibly dysfunctional, incredible, and insane, and that reshuffling is necessary to hold chromosomes together during egg-making. Despite this, they somehow manage to lay eggs. He never heard of such a thing before.
He goes further to explain that when just two chromosomes out of four are selected, and no new genetic material is added by a second parent, there is an average loss of one-third of genetic diversity with every generation.
Loss of genetic material would cause genetic diversity to become low enough to be deadly after just a few generations of parthenogenetic reproduction, as compared to most social insects that depend on a queen to breed sexually with males for genetic diversification on behalf of the entire hive. All workers then protect and care for all brood, as they are all closely related.
Cape honeybees usually reproduce according to the usual rules of social insect reproduction, he goes on to share, but their worker bees have a genetic mutation that allows them to lay eggs parthenogenetically with all the genetic material from the four chromosomes. This is what allows them to clone themselves for decades, whenever they like, despite it creating populations without genetic diversity.
What will this do over time to the balance of all-for-one and cooperation, in other words the unity that honeybees are known for, as compared to individuality? If they do not stick together, they may go extinct if social order collapses.
In the case of the parasitic behavior that one lineage of Cape bee workers exerts against African lowland honeybees, the rogue clones sneak into hives, lay as many eggs as they can, and let the African lowland honeybees raise them, thinking they are their own. The Cape bee workers exploiting the host bees are the genetically identical descendants of a single worker that lived in 1990, according to Oldroyd.
This Cape bee lineage is responsible for 10% collapse of African lowland honeybee colonies every year now. This trend could eventually create a devastating outcome for South African agriculture.
Researchers intend to study how queens can switch on the gene that enables recombination and how workers can switch it off. They will also study the parasitized African lowland hives to see what triggers their hives to collapse.
These findings were published by the researchers on June 9 in the journal Proceedings of the Royal Society B.