Indian red jungle fowl are genetically pure
it was believed that genetic contamination was driving the Indian red fowl to the verge of extinction. Inter-breeding with domestic chicken had upset their genetic integrity. But that may not be the case, a study has found out. India's native red jungle fowl are genetically pure, the study notes. It has also busted another belief. Earlier, domestication of chicken was considered to have occurred in southeast Asia from a species of red jungle fowl found in the region and from there more species spread to other parts of the world when people domesticated the chicken. The study suggests that domestication of chicken happened independently in India. It is not a variant of the southeast Asian domestic chicken (see box: Sub chicks).
For the study, researchers from Centre for DNA Fingerprinting and Diagnostics, Hyderabad, used 76 Indian birds (domestic chicken, red jungle fowl and grey jungle fowl) from seven different populations for genetic analysis. Blood samples were collected from geographically isolated populations in Haryana and various zoos. Some genetic information on Indian red jungle fowl and domestic chicken was obtained from the GeneBank of National Centre for Biotechnology Information--a public database of genome data in the us.
The researchers combined the results of two separate genetic analyses to conclude that there was no genetic exchange between the domestic chicken and the Indian red jungle fowl. The results brought to light evidences of separate inbreeding among the population of the red jungle fowl and domestic chicken, but not interbreeding. "Inbreeding clearly supports absence of any hybridization between Indian red jungle fowl and domestic birds in India and genetic impurity," the authors said in the study published in the June 2008 issue of BMC Evolutionary Biology (Vol 8, No 174). Changes in population over time leave characteristic molecular signatures and one can reconstruct the population history by measuring such changes, they added.
The researchers also constructed a phylogeny tree to come to the conclusion about the history of the species' lineage and genetic integrity. The tree showed a clear separation of domestic chicken from the Indian red jungle fowl. The tree also suggested genetic distinctness in the fowl population, ruling out any possibility of hybridization with domestic chicken. However, researchers clarify that rare instances of hybridization between Indian red jungle fowl and domestic birds cannot be ruled out.
The researchers found one such case in the course of their study. "Possible hybridization observed in previous studies could have been because of limited number of samples," say researchers. Besides native red jungle fowl not being included in earlier genetic studies, limited samples could also be a reason for the belief that domestic chickens originated from a common ancestor, the authors said.
"It was suspected that the domestic chicken is inter-breeding with the wild red jungle fowl, resulting in erosion of genetic purity of the wild birds. In the light of these reports it was important to assess the genetic uniqueness of Indian red jungle fowls," says an official of the Haryana Forest Department which initiated and funded the study. "The present study shows that the fowl displayed inbreeding not inter-breeding," he added.
Rahul Kaul, director of the Wild Species programme at Wildlife Trust of India says, "The findings should be used carefully. There was always doubt whether the assumption made about the red jungle fowl being threatened with extinction due to genetic contamination was true but it was a possibility and needed to be tested," argues Kaul. While a preliminary survey suggested that most specimens in captivity demonstrated physical traits similar to pure birds, but it has to be ascertained by molecular techniques on a nationwide basis. The present study on the other hand is only for three sites," said Kaul.
The findings could also be significant in controlling bird flu in future. The red jungle fowl are known to be resistant to the bird flu virus. Researchers say that since the domestic chicken in India descended from the Indian red jungle fowl, the response to the bird flu virus needs to be studied separately.
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