**4.5. Population expansion of Tibetan sheep populations**

The mismatch distribution analysis of the complete dataset, maternal lineages A, B, C, D, and 15 Tibetan sheep populations of the mtDNA D-loop, is presented [29]. Neutrality tests (Ewens-Watterson test, Chakraborty's test, Tajima's D test, Fu's FS test) were used to detect population expansion [29]. The complete dataset of all Tibetan sheep populations had a significantly large negative Tajima's D value and *FS* value. This result shows two large and sudden expansions, consistent with a demographic model, as inferred from the mismatch distribution. The mismatch distribution of the complete dataset suggested that there were two major peaks with maximum values at 4 and 27 pairwise differences and two smaller peaks at 45 and 51 differences. Based on the results, it could be implied that there are at least two expansion events occurred in the population demographic history of the Tibetan sheep, which live on the Qinghai-Tibetan Plateau. The mismatch distribution analysis revealed a unimodal bell-shaped distribution of the pairwise sequence differences in maternal lineages A, B and C. However, the distribution of maternal lineage D was a sambong function, duo to the geographic distribution patterns of species diversity. Mismatch analysis of maternal lineages A, B, and C suggested that it happened in the demographic history of Tibetan sheep populations that single population expansion events occurred before. Similar results were found in previous reports [42, 43].

showed that four maternal lineages (A, B, C and D), previously defined, could be identified in the 636 tested individuals of the 15 Tibetan sheep populations. The estimation of demographic parameters from the mismatch analyses shows that maternal lineages A, B and C had at least one demographic expansion in the Tibetan sheep of the Qinghai-Tibetan Plateau

Phylogenetic Evolution and Phylogeography of Tibetan Sheep Based on mtDNA D-Loop Sequences

http://dx.doi.org/10.5772/intechopen.76583

147

The authors appreciated constructive comments from the editor Hervé Seligmann. This work was supported by the special fund from the Major International (Regional) Joint Research Project (NSFC-CGIAR 31461143020), and Gansu Provincial Agricultural biotechnology research and application projects (GNSW-2014-21, GNSW-2016-13), and the Central Level,

This study did not involve endangered or protected Tibetan sheep populations. All experimental and sampling procedures were approved by the Institutional Animal Care and Use Committee, Lanzhou Institute of Husbandry and Pharmaceutical Sciences, Peoples Republic

Conceived and designed the experiments: LJB DXZ ZYF GX SXP. Performed the experiments: LJB DXZ ZYF GX SXP. Analyzed the data: GX SXP YC. Wrote the paper: LJB DXZ ZYF GX YC.

1 Lanzhou Institute of Husbandry and Pharmaceutical Sciences of the Chinese Academy of

2 Sheep Breeding Engineering Technology Research Center of Chinese Academy of

, Xian Guo1†‡

, Xiaoping Sun1,2†‡

and

, Yufeng Zeng1†‡

Scientific Research Institutes for Basic R & D Special Fund Business (1610322016016).

areas.

**Acknowledgements**

**Conflict of interest**

**Author contributions**

\*, Xuezhi Ding1†‡

Agricultural Sciences, Lanzhou, China

Agricultural Sciences, Lanzhou, China

\*Address all correspondence to: liujianbin@caas.cn

These authors contributed equally to this work

These authors are co-first authors on this work

**Author details**

Jianbin Liu1,2†‡

Chao Yuan1,2†‡

†

‡

of China.
