Laboratoire des Productions Animales et Fourragères, Institut National de la Recherche Agronomique de Tunisie, Université de Carthage, Ariana, Tunisia.
Livestock and Wildlife Laboratory, Arid Lands Institute, Route Djorf Km 22, 4119, Medenine, Tunisia.
Anim Genet. 2019 Oct;50(5):526-533. doi: 10.1111/age.12831. Epub 2019 Aug 5.
North Africa has a great diversity of indigenous sheep breeds whose origin is linked to its environmental characteristics and to certain historical events that took place in the region. To date, few genome-wide studies have been conducted to investigate the population structure of North African indigenous sheep. The objective of the present study was to provide a detailed assessment of the genetic structure and admixture patterns of six Maghreb sheep populations using the Illumina 50K Ovine BeadChip and comparisons with 22 global populations of sheep and mouflon. Regardless of the method of analysis used, patterns of multiple hybridization events were observed within all North African populations, leading to a heterogeneous genetic architecture that varies according to the breed. The Barbarine population showed the lowest genetic heterogeneity and major southwest Asian ancestry, providing additional support to the Asian origin of the North African fat-tailed sheep. All other breeds presented substantial Merino introgression ranging from 15% for D'man to 31% for Black Thibar. We highlighted several signals of ancestral introgression between North African and southern European sheep. In addition, we identified two opposite gradients of ancestry, southwest Asian and central European, occurring between North Africa and central Europe. Our results provide further evidence of the weak global population structure of sheep resulting from high levels of gene flow among breeds occurring worldwide. At the regional level, signs of recent admixture among North African populations, resulting in a change of the original genomic architecture of minority breeds, were also detected.
北非拥有丰富多样的本土绵羊品种，其起源与该地区的环境特征和某些历史事件有关。迄今为止，针对北非本土绵羊的群体结构，仅有少数全基因组研究。本研究的目的是利用 Illumina 50K 绵羊基因芯片，对六个马格里布绵羊群体进行详细的遗传结构和混合模式评估，并与 22 个全球绵羊和摩弗伦羊群体进行比较。无论使用哪种分析方法，所有北非群体都观察到多次杂交事件的模式，导致遗传结构异质，这因品种而异。巴巴里羊群体显示出最低的遗传异质性和主要的西南亚祖先，为北非肥尾羊的亚洲起源提供了额外的支持。其他所有品种都有大量的美利奴羊的渗入，从 D'man 的 15%到 Black Thibar 的 31%。我们强调了北非和南欧绵羊之间存在一些祖先渗入的信号。此外，我们还发现了西南亚和中欧之间的两个相反的祖先梯度，这两个梯度存在于北非和中欧之间。我们的研究结果进一步证明了由于世界各地品种间基因流水平较高，导致绵羊的全球群体结构较弱。在区域层面上，还检测到北非群体之间存在近期混合的迹象，导致少数品种原始基因组结构发生变化。
