The wild species genome ancestry of domestic chickens

Hybridization and/or introgression play a key role in the evolutionary history of animal species. It is commonly observed in several orders in wild birds. The domestic chicken Gallus gallus domesticus is the commonest livestock species exploited for the benefit of mankind. The origin of its diversity remains unsettled. Here, we report a genome-wide analyses for signatures of introgression within domestic village chicken. We first established the genome-wide phylogeny and divergence time across the genus Gallus, showing the sister relationships between Grey junglefowl G. sonneratii and Ceylon junglefowl G. lafayettii and that the Green junglefowl is the first diverging lineage within the genus Gallus. Then, by analysing the whole-genome sequences of geographically diverse chicken populations, we reveal extensive bidirectional introgression between Grey junglefowl and domestic chicken and to a much less extent with Ceylon junglefowl. A single case of Green junglefowl G. varius introgression was identified. These introgressed regions include biological functions related to the control of gene expression. Our results show that while the Red junglefowl is the main ancestral species, introgressive hybridization episodes have impacted the genome and contributed to the diversity of domestic chicken, although likely at different level across its geographic range.