Too many crosses between chickens and red junglefowl threaten to destroy the latter’s genetic diversity.
We owe chickens a lot. For example, a Dutch person eats an average of 210 eggs and at least 20 kg of chicken meat per year. But for the wild urchin, the red jungle fowl, the chicken’s success is less good news. Its gene package, or genome, is in danger of being destroyed by too much chicken DNA due to a multitude of crosses. A research team from the National University of Singapore has recorded it PLOS Genetics.
The development of Gallus gallus domesticus, or the domesticated chicken, began in Thailand between 10,000 and 3,000 years ago. The population then began to cultivate rice, which attracted flocks of red junglefowl (Gallus gallus spadiceus) at Roaming among those rice fields, they got used to humans and vice versa. Due to the abundant amount of food, the animals then started laying more eggs and gradually changed into farm chickens.
Despite their differences, chickens and red junglefowl can still mate and produce offspring. Especially in areas where the animals can roam freely, as is often the case in Asia. And that now appears to be a problem, researchers led by Franck Rheindt have determined.
The team examined and compared the genomes of 51 chickens and 63 red junglefowl. Some of the specimens came from a museum and were therefore somewhat older. This also allowed the researchers to compare the genomes over time. What turned out? In recent decades, more and more chicken DNA has appeared in the genome of its wild ancestor. Rheindt and colleagues estimate that 20 to 50 percent of the current genes for red junglefowl now come from chickens.
“It is not surprising that the DNA of wild and domestic animals of the same species is mixed over time,” says biologist and geneticist Manon de Visser of the Naturalis Biodiversity Center and Leiden University. “We also see this in, for example, pigs and wild boar. But what strikes me is the found percentage of up to 50 percent. I find that quite shocking!”
That too fall of the chicken?
And the huge mix is not good, continues De Visser. “Compare that to dogs and wolves: If all wolves were slowly turning into pugs, chihuahuas and golden retrievers, they probably wouldn’t last long in the wild. Chicken DNA has diverged significantly from the ancestral genome due to the breeding process. If wild junglefowl then inheriting that DNA, they are no longer as well adapted to their natural habitat and may even become extinct in the long run.”
It could also just be news to the chicken. Because, according to the researchers, the wild gerbil also functions as a genetic reservoir. This means we can take advantage of this (read: targeted breeding) to improve the chickens. For example, to make them more resistant to certain diseases. “The loss of the red junglefowl could in the worst case also mean that the modern chicken, an important food source for humans, declines,” says De Visser, who is also very satisfied with the way the research was carried out.
It is therefore important to protect the red junglefowl. How do we do it? Preventing mating is easier said than done, especially in areas where chickens roam free. “The foraging behavior is of course important for their well-being. But it is certainly also good to create a stricter demarcation between wild and domesticated groups. Genetic monitoring of wild animals is also important. Fortunately, there are already working groups and breeding programs specifically for jungle birds.” Hopefully, this research will help emphasize the importance of these initiatives.
Sources: PLOS Genetics, PLOS News via EurekAlert!
Image: Lip Kee/CC BY-SA 2.0