Department of Agriculture Environment and Food Science, University of Molise, Campobasso, Italy.
Consortium for Experimentation, Dissemination, and Application of Innovative Biotechniques, (ConSDABI), Benevento, Italy.
PLoS One. 2023 Oct 18;18(10):e0291814. doi: 10.1371/journal.pone.0291814. eCollection 2023.
Livestock European diffusion followed different human migration waves from the Fertile Crescent. In sheep, at least two diffusion waves have shaped the current breeds' biodiversity generating a complex genetic pattern composed by either primitive or fine-wool selected breeds. Nowadays most of the sheep European breeds derive from the second wave which is supposed to have largely replaced oldest genetic signatures, with the exception of several primitive breeds confined on the very edge of Northern Europe. Despite this, some populations also in the Mediterranean region are characterised by the presence of phenotypic traits considered ancestral such as the policeraty, large horns in the ram, short tail, and a moulting fleece. Italy is home of a large number of local breeds, albeit some are already extinct, others are listed as critically endangered, and among these there is the Quadricorna breed which is a four-horned sheep characterised by several traits considered as ancestral. In this context we genotyped 47 individuals belonging to the Quadricorna sheep breed, a relict and endangered breed, from Central and Southern Italy. In doing so we used the Illumina OvineSNP50K array in order to explore its genetic diversity and to compare it with other 41 breeds from the Mediterranean region and Middle-East, with the specific aim to reconstruct its origin. After retaining 32,862 SNPs following data filtering, the overall genomic architecture has been explored by using genetic diversity indices, Principal Component Analysis (PCA) and admixture analysis, while the genetic relationships and migration events have been inferred using a neighbor-joining tree based on Reynolds' distances and by the maximum likelihood tree as implemented in treemix. The Quadricorna breed exhibit genetic diversity indices comparable with those of most of the other analysed breeds, however, the two populations showed opposing patterns of genetic diversity suggesting different levels of genomic inbreeding and drift (FIS and FROH). In general, all the performed genome-wide analyses returned complementary results, indicating a westward longitudinal cline compatible with human migrations from the Middle-East and several additional genetic footprints which might mirror more recent historical events. Interestingly, among the Italian breeds, the original Quadricorna (QUAD_SA) first separated showing its own ancestral component. In addition, the admixture analysis does not suggest any signal of recent gene exchange with other Italian local breeds, highlighting a rather ancestral purity of this population. On the other hand, both the neighbor-joining tree and the treemix analysis seem to suggest a proximity of the Quadricorna populations to breeds of South-Eastern Mediterranean origin. Although our results do not support a robust link between the genetics of the first wave and the presence of primitive traits, the observed genetic uniqueness together with the inferred phylogeograpic reconstruction would suggest an ancient presence of the Quadricorna breed in the Italian Peninsula. Because of this singularity, urgent conservation actions are needed in order to keep the breed and all related cultural products alive.
家畜在欧洲的传播是随着人类从新月沃地的不同迁徙浪潮进行的。在绵羊中,至少有两次传播浪潮塑造了当前品种的生物多样性,产生了由原始或细毛品种组成的复杂遗传模式。如今,大多数欧洲绵羊品种都源自第二次浪潮,这一浪潮可能已经在很大程度上取代了最古老的遗传特征,除了北欧几个原始品种之外。尽管如此,一些地中海地区的种群也具有被认为是原始的表型特征,如公绵羊的 policeraty、大角、短尾和季节性换毛。意大利是大量本地品种的发源地,尽管有些品种已经灭绝,有些品种被列为极度濒危品种,其中就包括 Quadricorna 品种,这是一种具有多种被认为是原始特征的四角绵羊。在这种情况下,我们对来自意大利中部和南部的 47 只属于 Quadricorna 绵羊品种的个体进行了基因分型,该品种是一种古老而濒危的品种。为此,我们使用了 Illumina OvineSNP50K 芯片,以探索其遗传多样性,并将其与来自地中海地区和中东的其他 41 个品种进行比较,目的是重建其起源。在对数据进行过滤后保留了 32862 个 SNP 后,我们通过遗传多样性指数、主成分分析(PCA)和混合分析来探索其基因组结构,同时通过基于 Reynolds 距离的邻接树和 treemix 中实现的最大似然树来推断遗传关系和迁移事件。Quadricorna 品种的遗传多样性指数与大多数其他分析品种相当,然而,两个种群显示出相反的遗传多样性模式,表明基因组近亲繁殖和漂变(FIS 和 FROH)的程度不同。一般来说,所有进行的全基因组分析都得出了互补的结果,表明这与从中东地区开始的人类迁徙相一致,并且存在其他一些遗传痕迹,可能反映了更近的历史事件。有趣的是,在意大利品种中,原始的 Quadricorna(QUAD_SA)首先分离出来,显示出其自身的原始成分。此外,混合分析并没有表明与其他意大利本地品种有任何近期基因交流的信号,突出了该种群的相当原始的纯度。另一方面,邻接树和 treemix 分析似乎都表明,Quadricorna 种群与东南地中海起源的品种之间存在亲缘关系。尽管我们的结果不支持第一次浪潮的遗传与原始特征之间存在强有力的联系,但观察到的遗传独特性以及推断的系统地理学重建表明,Quadricorna 品种在意大利半岛的存在非常古老。由于这种独特性,需要采取紧急保护措施,以保持该品种及其所有相关文化产品的活力。