Abstract：
Extant Old World camels (genus Camelus) contributed to the economic and cultural exchanges between the East and West for thousands of years.1,2 Although many remains have been unearthed,3,4,5 we know neither whether the prevalent hybridization observed between extant Camelus species2,6,7 also occurred between extinct lineages and the ancestors of extant Camelus species nor why some populations became extinct while others survived. To investigate these questions, we generated paleogenomic and stable isotope data from an extinct two-humped camel species, Camelus knoblochi. We find that in the mitochondrial phylogeny, all C. knoblochi form a paraphyletic group that nests within the diversity of modern, wild two-humped camels (Camelus ferus). In contrast, they are clearly distinguished from both wild and domesticated (Camelus bactrianus) two-humped camels on the nuclear level. Moreover, the divergence pattern of the three camel species approximates a trifurcation, because the most common topology is only slightly more frequent than the two other possible topologies. This mito-nuclear phylogenetic discordance likely arose due to interspecific gene flow between all three species, suggesting that interspecific hybridization is not exclusive to modern camels but a recurrent phenomenon throughout the evolutionary history of the genus Camelus. These results suggest that the genomic complexity of Old World camels\' evolutionary history is underestimated when considering data from only modern species. Finally, we find that C. knoblochi populations began declining prior to the last glacial maximum and, by integrating palaeoecological evidence and stable isotope data, suggest that this was likely due to failure to adapt to a changing environment.
摘要：
现存的旧世界骆驼（骆驼属）几千年来为东西方之间的经济和文化交流做出了贡献。1,2尽管出土了许多遗骸，3,4,5我们既不知道在现存的骆驼物种2,6,7之间观察到的普遍杂交是否也发生在已灭绝的谱系和现存的骆驼物种的祖先之间，也不知道为什么某些种群灭绝而另一些种群幸存下来。为了调查这些问题，我们从已灭绝的双峰骆驼物种中获得了古基因组和稳定同位素数据，CamelusKnoblochi.我们发现在线粒体系统发育中，所有C.knoblochi都形成了一个共生的群体，在现代的多样性中筑巢，野生双峰骆驼（Camelusferus）。相比之下,在核水平上，它们与野生和驯化的（Camelusbactrianus）双峰骆驼明显不同。此外，三种骆驼的发散模式近似为三分叉，因为最常见的拓扑仅比其他两种可能的拓扑稍微频繁一些。这种mito核系统发育不一致可能是由于所有三个物种之间的种间基因流动引起的，表明种间杂交并非现代骆驼独有，而是在骆驼属的进化史上反复出现的现象。这些结果表明，当仅考虑来自现代物种的数据时，旧世界骆驼进化史的基因组复杂性被低估了。最后,我们发现C.knoblochi种群在最后一次冰川最大值之前开始下降，通过整合古生态证据和稳定同位素数据，这可能是由于未能适应不断变化的环境。
