摘要
真猛犸象(Mammuthus primigenius)是中国北方猛犸象-披毛犀动物群的核心动物,在晚更新世时期广泛分布于欧亚和北美的中高纬度地区,在我国则主要分布在东北一带.针对中国东北地区的真猛犸象材料的基因组层面的研究极为匮乏,导致其分类和溯源问题不甚明朗.本研究获取到中国东北16个真猛犸象样品的完整或部分线粒体基因组序列,并对样品进行放射性碳同位素测年或分子定年.线粒体基因组系统发育树显示,在晚更新世时期的中国东北地区分布有猛犸象全部已知3个线粒体遗传支系(Clade Ⅰ、Clade Ⅱ和Clade Ⅲ),该时期该地区的猛犸象种群遗传多样性较高.样品年代信息及各地种群的线粒体遗传结构表明,Clade Ⅰ与Clade Ⅱ、Ⅲ的共同祖先在约163万年前的分化对应着草原猛犸象从欧亚到北美的第一次迁徙事件;在Clade Ⅰ内部,中国东北种群与晚更新世时期第二次迁向北美的种群在61万年前已发生分歧.此外,本研究在中国东北真猛犸象样品中发现Clade Ⅱ支系个体,表明该支系代表的种群曾广泛分布于东北亚;在末次盛冰期来临前,该种群可能发生了栖居地缩减并在中国东北形成小规模种群.本研究为探究中国东北真猛犸象的系统发育地位、遗传多样性及真猛犸象对晚更新世气候变化的响应提供了分子依据.
Abstract
As one of the representatives of extinct mammals in Late Quaternary,Mammuthus primigenius was widely distributed across middle-to-high latitude regions of Eurasia and North America.In China,it was mainly distributed in the northeast and represented not only the core member of the Mammuthus-Coelodonta fauna in Northern China during the Late Pleistocene,but also a key component of this hot spot species from mid-latitude region in Asia.Compared to the comprehensive paleogenomic exploration of its counterparts from Europe,Siberia,and North America,M.primigenius remains in Northeastern China have only been molecularly investigated using short mitochondrial fragments and thus the genomic level is inadequate.Therefore,the phylogenetic relationship of the woolly mammoth in China to Eurasian and North American individuals remains an open question.Moreover,paleontologists have suggested classifying the woolly mammoth from Northeastern China as a separate species based on its morphological characters.Here,we performed ancient DNA extraction,sequencing library construction and next-generation sequencing(NGS)on woolly mammoth fossils collected in Northern and Northeastern China.By data filtering and mapping to reference genome,we obtained high-quality complete mitochondrial genomes or partial mitochondrial sequences from 16 individuals.We carried out radiocarbon isotope dating for three out of these 16 samples and obtained dates for the rest either from the literature or by molecular dating.We ran mapDamage to authenticate our data as ancient and confirm substitution characteristics typical of ancient DNA sequences.Phylogenetic analyses based on our newly obtained mitochondrial sequences and published mitogenomic data showed that all three known mitochondrial clades of M.primigenius are present in the analyzed Chinese woolly mammoths.Specifically,among the 16 individuals,there are nine individuals clustered with M.primigenius from Northern Siberia and central Asia in Clade Ⅰ;six individuals clustered with samples from Northeastern Asia to form CladeⅡ;one individual belonged to Clade Ⅲ.The placement in multiple clades suggests that M.primigenius in Northeastern China had relatively high mitochondrial diversity.In a Bayesian phylogenetic using complete mitochondrial genomes of five of our Northeastern Chinese individuals and other published individuals from Asia and North America,the available age information of all individuals and their mitochondrial genetic structure show that Clade Ⅰ and Clade Ⅱ+Ⅲ diverged from each other approximately 1.63 Ma,corresponding to the first migration event of the woolly mammoth from Eurasia to North America.A second migration was detected within Clade Ⅰ,in which a population in Northeastern China split from the ancestral woolly mammoth population that headed into North America around 0.61 Ma.In addition,it is the first time that individuals belonged to Clade Ⅱ have been identified from Northeastern China,which indicates that the population represented by Clade Ⅱ was once widely distributed in Northeast Asia in the Late Pleistocene.Prior to the Last Glacial Maximum(LGM),this population probably experienced habitat contraction and remained as a small population in Northeastern China,since the only individual that dated close to LGM has only be found in this region.Overall,we provide mitogenomic insights into both the phylogenetic positions and genetic diversity of M.primigenius in China,as well as the response of woolly mammoths to the Late Pleistocene climate change.
维普
万方数据