Ancient Mitogenomes Provide New Insights into the Origin and Early Introduction of Chinese Domestic Donkeys.

Linying Wang,Michael Hofreiter,Bo Xiao,Xulong Lai,Xindong Hou,Tao Deng,Songmei Hu,Guilian Sheng,Michaela Preick,Junxia Yuan,Shiwen Song,Ulrike H Taron,Guojiang Sun,Jiaming Hu,Axel Barlow

doi:10.3389/fgene.2021.759831

Abstract

Both molecular data and archaeological evidence strongly support an African origin for the domestic donkey. Recent genetic studies further suggest that there were two distinct maternal lineages involved in its initial domestication. However, the exact introduction time and the dispersal process of domestic donkeys into ancient China are still unresolved. To address these questions, we retrieved three near-complete mitochondrial genomes from donkey specimens excavated from Gaoling County, Shaanxi Province, and Linxia Basin, Gansu Province, China, dated at 2,349-2,301, 469-311, and 2,160-2,004 cal. BP, respectively. Maximum-likelihood and Bayesian phylogenetic analyses reveal that the two older samples fall into the two different main lineages (i.e., clade Ⅰ and clade Ⅱ) of the domestic donkey, suggesting that the two donkey maternal lineages had been introduced into Midwestern China at least at the opening of Silk Road (approximately the first century BC). Bayesian analysis shows that the split of the two donkey maternal lineages is dated at 0.323 Ma (95% CI: 0.583–0.191 Ma) using root-tip dating calibrations based on near-complete mitogenomes, supporting the hypothesis that modern domestic donkeys go back to at least two independent domestication events. Moreover, Bayesian skyline plot analyses indicate an apparent female population increase between 5,000 and 2,500 years ago for clade I followed by a stable population size to the present day. In contrast, clade II keeps a relatively stable population size over the past 5,000 years. Overall, our study provides new insights into the early domestication history of Chinese domestic donkeys.

Highlights

The domestication of the donkey (Equus asinus) is a vital event in human history, which played a significant role in the development of human civilization (Liu et al, 2010; Bai et al, 2017; Wang et al, 2020)
Two specimens (SG1 and SG3) were excavated from Gaoling County, Shaanxi Province, China and one sample (LXH1) was collected from Linxia Basin, Gansu Province, China (Figure 1). 14C dating of the samples was performed by accelerator mass spectrometry (AMS) at the Archaeological Geochronology Laboratory of Peking University (PKUAMS, China)
Detailed information on the samples is listed in Supplementary Table S1

Summary

INTRODUCTION

The domestication of the donkey (Equus asinus) is a vital event in human history, which played a significant role in the development of human civilization (Liu et al, 2010; Bai et al, 2017; Wang et al, 2020). Wang et al (2020) recently analyzed 126 modern domestic donkey nuclear genomes Their D-statistic analysis showed an African domestication of donkeys, consistent with the results from mitochondrial DNA, and indicated its subsequent spread to Europe and Asia. Wang et al (2020) analyzed mitochondrial DNA and nuclear genomes of Chinese local donkey breeds and revealed that Chinese donkeys are closer to African wild asses than to Asian wild asses (E. hemionus and Equus kiang). The only public report on genetic analyses of Chinese ancient donkeys has been presented by Han et al (2014), but only mitochondrial DNA D-loop and cytochrome b gene fragments were obtained, with the dates of the analyzed samples ranging between 1,200–550 years before present (BP). Our study provides new insights into the early domestication history of Chinese donkeys

RESULTS AND DISCUSSION

METHODS

ETHICS STATEMENT