Der Sarkissian Clio, Vilstrup Julia T, Schubert Mikkel, Seguin-Orlando Andaine, Eme David, Weinstock Jacobo, Alberdi Maria Teresa, Martin Fabiana, Lopez Patricio M, Prado Jose L, Prieto Alfredo, Douady Christophe J, Stafford Tom W, Willerslev Eske, Orlando Ludovic
Centre for GeoGenetics, Natural History Museum of Denmark, University of Copenhagen, Øster Voldgade 5-7, 1350 Copenhagen K, Denmark.
Centre for GeoGenetics, Natural History Museum of Denmark, University of Copenhagen, Øster Voldgade 5-7, 1350 Copenhagen K, Denmark Danish National High-throughput DNA Sequencing Centre, Øster Farimagsgade 2D, 1353 Copenhagen K, Denmark.
Biol Lett. 2015 Mar;11(3). doi: 10.1098/rsbl.2014.1058.
Hippidions were equids with very distinctive anatomical features. They lived in South America 2.5 million years ago (Ma) until their extinction approximately 10 000 years ago. The evolutionary origin of the three known Hippidion morphospecies is still disputed. Based on palaeontological data, Hippidion could have diverged from the lineage leading to modern equids before 10 Ma. In contrast, a much later divergence date, with Hippidion nesting within modern equids, was indicated by partial ancient mitochondrial DNA sequences. Here, we characterized eight Hippidion complete mitochondrial genomes at 3.4-386.3-fold coverage using target-enrichment capture and next-generation sequencing. Our dataset reveals that the two morphospecies sequenced (H. saldiasi and H. principale) formed a monophyletic clade, basal to extant and extinct Equus lineages. This contrasts with previous genetic analyses and supports Hippidion as a distinct genus, in agreement with palaeontological models. We date the Hippidion split from Equus at 5.6-6.5 Ma, suggesting an early divergence in North America prior to the colonization of South America, after the formation of the Panamanian Isthmus 3.5 Ma and the Great American Biotic Interchange.
希氏马是具有非常独特解剖特征的马科动物。它们在250万年前生活在南美洲，直至约1万年前灭绝。已知的三种希氏马形态物种的进化起源仍存在争议。根据古生物学数据，希氏马可能在1000万年前就已从导致现代马科动物的谱系中分化出来。相比之下，部分古代线粒体DNA序列表明其分化时间要晚得多，希氏马嵌套在现代马科动物之中。在此，我们利用靶向富集捕获和新一代测序技术，以3.4至386.3倍的覆盖率对8个希氏马完整线粒体基因组进行了特征分析。我们的数据集显示，测序的两个形态物种（萨尔迪亚希氏马和主要希氏马）形成了一个单系类群，位于现存和已灭绝的马属谱系的基部。这与之前的基因分析结果相反，并支持希氏马作为一个独特的属，这与古生物学模型一致。我们确定希氏马与马属的分化时间为560万至650万年前，这表明在350万年前巴拿马地峡形成和大美洲生物交流之后，希氏马在南美洲殖民之前就已在北美洲早期分化。
