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Domestic sheep and their wild relatives harbor substantial genetic variants that can form the backbone of molecular breeding, but their genome landscapes remain understudied. Here, we present a comprehensive genome resource for wild ovine species, landraces and improved breeds of domestic sheep, comprising high-coverage (∼16.10×) whole genomes of 810 samples from 7 wild species and 158 diverse domestic populations. We detected, in total, ∼121.2 million single nucleotide polymorphisms, ∼61 million of which are novel. Some display significant (P < 0.001) differences in frequency between wild and domestic species, or are private to continent-wide or individual sheep populations. Retained or introgressed wild gene variants in domestic populations have contributed to local adaptation, such as the variation in the HBB associated with plateau adaptation. We identified novel and previously reported targets of selection on morphological and agronomic traits such as stature, horn, tail configuration, and wool fineness. We explored the genetic basis of wool fineness and unveiled a novel mutation (chr25: T7,068,586C) in the 3′-UTR of IRF2BP2 as plausible causal variant for fleece fiber diameter. We reconstructed prehistorical migrations from the Near Eastern domestication center to South-and-Southeast Asia and found two main waves of migrations across the Eurasian Steppe and the Iranian Plateau in the Early and Late Bronze Ages. Our findings refine our understanding of genome variation as shaped by continental migrations, introgression, adaptation, and selection of sheep., This study was financially supported by grants from the National Natural Science Foundation of China (Nos. 32061133010, 31825024, 31661143014, and 31972527), the National Key Research and Development Program-Key Projects of International Innovation Cooperation between Governments (2017YFE0117900), the External Cooperation Program of Chinese Academy of Sciences (152111KYSB20150010), and the Second Tibetan Plateau Scientific Expedition and Research Program (STEP) (No. 2019QZKK0501), and the Special Funds of the State Key Laboratory of Sheep Genetic Improvement and Healthy Production (Nos. 2018CA001, and 2019CA009, 2020CA001).

Additional file 1: Fig. S1. mtDNA D-loop variation of 88 haplotypes found in the 706 village chicken. Fig. S2. Median-Joining network for Algerian haplotypes (n = 13). Fig. S3. Median-Joining network for Ethiopian haplotypes (n = 36). Fig. S4. Median-Joining network for Iraqi haplotypes (n = 18). Fig. S5. Median-Joining network for Libyan haplotypes (n = 10). Fig. S6. Median-Joining network for Pakistani haplotypes (n = 19). Fig. S7. Median-Joining network for Saudi Arabia haplotypes (n = 26). Fig. S8. Maximum likelihood tree for the 136 haplotypes and references from Liu et al. [14]. Fig. S9. Median-Joining network for 136 haplotypes of the collected and downloaded samples. Fig. S10. Mismatch distribution patterns of populations included in this study. Table S1. Downloaded sequences from GeneBank. Table S2a. Haplotype diversity significant differences among Iraqi populations. Table S2b. Nucleotide diversity significant differences among Iraqi populations. Table S3a. Haplotype diversity significant differences among Algerian populations. Table S3b. Nucleotide diversity significant differences among Algerian populations. Table S4a. Haplotype diversity significant differences among Ethiopian populations. Table S4b. Nucleotide diversity significant differences among Ethiopian populations. Table S5a. Haplotype diversity significant differences among Saudi regions. Table S5b. Nucleotide diversity significant differences among Saudi regions. Table S6. Location, sample size and genetic diversity of haplogroup E.

BACKGROUND: Hybridisation and introgression play key roles in the evolutionary history of animal species. They are commonly observed within several orders in wild birds. The domestic chicken Gallus gallus domesticus is the most common livestock species. More than 65 billion chickens are raised annually to produce meat and 80 million metric tons of egg for global human consumption by the commercial sector. Unravelling the origin of its genetic diversity has major application for sustainable breeding improvement programmes. RESULTS: In this study, we report genome-wide analyses for signatures of introgression between indigenous domestic village chicken and the four wild Gallus species. We first assess the genome-wide phylogeny and divergence time across the genus Gallus. Genome-wide sequence divergence analysis supports a sister relationship between the Grey junglefowl G. sonneratii and Ceylon junglefowl G. lafayettii. Both species form a clade that is sister to the Red junglefowl G. gallus, with the Green junglefowl G. varius the most ancient lineage within the genus. We reveal extensive bidirectional introgression between the Grey junglefowl and the domestic chicken and to a much lesser extent with the Ceylon junglefowl. We identify a single case of Green junglefowl introgression. These introgressed regions include genes with biological functions related to development and immune system. CONCLUSIONS: Our study shows that while the Red junglefowl is the main ancestral species, introgressive hybridisation episodes have impacted the genome and contributed to the diversity of the domestic chicken, although likely at different levels across its geographic range.

Background: Hybridisation and introgression play key roles in the evolutionary history of animal species. They are commonly observed within several orders in wild birds. The domestic chicken Gallus gallus domesticus is the most common livestock species. More than 65 billion chickens are raised annually to produce meat and 80 million metric tons of egg for global human consumption by the commercial sector. Unravelling the origin of its genetic diversity has major application for sustainable breeding improvement programmes. Results: In this study, we report genome-wide analyses for signatures of introgression between indigenous domestic village chicken and the four wild Gallus species. We first assess the genome-wide phylogeny and divergence time across the genus Gallus. Genome-wide sequence divergence analysis supports a sister relationship between the Grey junglefowl G. sonneratii and Ceylon junglefowl G. lafayettii. Both species form a clade that is sister to the Red junglefowl G. gallus, with the Green junglefowl G. varius the most ancient lineage within the genus. We reveal extensive bidirectional introgression between the Grey junglefowl and the domestic chicken and to a much lesser extent with the Ceylon junglefowl. We identify a single case of Green junglefowl introgression. These introgressed regions include genes with biological functions related to development and immune system. Conclusions: Our study shows that while the Red junglefowl is the main ancestral species, introgressive hybridisation episodes have impacted the genome and contributed to the diversity of the domestic chicken, although likely at different levels across its geographic range.