The red junglefowl — the chicken’s wild ancestor — is losing its genetic diversity through interbreeding with domestic birds, according to a new study led by Frank Rheindt of the National University of Singapore, published Jan. 19 in the journal PLOS Genetics.
Humans domesticated the red junglefowl in tropical Asia sometime between 3,000 and 10,000 years ago, but wild and domestic birds can still interbreed. This is a concern for red bush fowl conservation because as wild populations acquire more DNA from chickens, they may lose their genetic diversity, potentially making them less resilient to changes in their environment.
In the new study, researchers compared whole genomes of 51 chickens and 63 junglefowl from the wild bird’s natural range, to find signs of interbreeding. They saw DNA from domestic chickens moving into wild junglefowl, and the magnitude of that movement has increased in recent decades. Comparing modern wild genomes with red junglefowl genomes from about a century ago, the researchers estimate that the wild birds have inherited 20% to 50% of their genomes from domestic birds, depending on their location. The study also identified eight genes that differed greatly between domesticated chickens and their wild ancestors, which were likely key to the development of the chicken as a livestock animal. These genes are involved in development, reproduction and vision.
The results of the study highlight the ongoing loss of genetic diversity in the wild junglefowl, and the researchers suggest efforts may be needed to protect the genome. In addition, wild populations have agricultural value because they can serve as a reservoir of genetic diversity that researchers can use to improve domesticated species, for example by finding genetic variants that make an animal more resistant to a particular disease. The loss of that genetic diversity in red junglefowl could hamper scientists’ ability to protect one of humanity’s most important food sources.
The authors add: “Taken from 100-year-old birds show that modern wild junglefowl, on average, carry more domesticated DNA than in the past. The wild genotype is an important reservoir of chicken genetic diversity and its conservation is critical.”
- Wu MY, Forcina G, Low GW, Sadanandan KR, Gwee CY, van Grouw H, et al. (2023) Historical samples reveal loss of wild genotype due to introgression of domestic chickens during the Anthropocene. PLoS Genet 19(1): e1010551. DOI: 10.1371/journal.pgen.1010551