Vershinina Alisa O, Heintzman Peter D, Froese Duane G, Zazula Grant, Cassatt-Johnstone Molly, Dalén Love, Der Sarkissian Clio, Dunn Shelby G, Ermini Luca, Gamba Cristina, Groves Pamela, Kapp Joshua D, Mann Daniel H, Seguin-Orlando Andaine, Southon John, Stiller Mathias, Wooller Matthew J, Baryshnikov Gennady, Gimranov Dmitry, Scott Eric, Hall Elizabeth, Hewitson Susan, Kirillova Irina, Kosintsev Pavel, Shidlovsky Fedor, Tong Hao-Wen, Tiunov Mikhail P, Vartanyan Sergey, Orlando Ludovic, Corbett-Detig Russell, MacPhee Ross D, Shapiro Beth
Ecology and Evolutionary Biology, University of California Santa Cruz, Santa Cruz, CA, USA.
The Arctic University Museum of Norway, UiT - The Arctic University of Norway, Tromsø, Norway.
Mol Ecol. 2021 Dec;30(23):6144-6161. doi: 10.1111/mec.15977. Epub 2021 May 27.
The Bering Land Bridge (BLB) last connected Eurasia and North America during the Late Pleistocene. Although the BLB would have enabled transfers of terrestrial biota in both directions, it also acted as an ecological filter whose permeability varied considerably over time. Here we explore the possible impacts of this ecological corridor on genetic diversity within, and connectivity among, populations of a once wide-ranging group, the caballine horses (Equus spp.). Using a panel of 187 mitochondrial and eight nuclear genomes recovered from present-day and extinct caballine horses sampled across the Holarctic, we found that Eurasian horse populations initially diverged from those in North America, their ancestral continent, around 1.0-0.8 million years ago. Subsequent to this split our mitochondrial DNA analysis identified two bidirectional long-range dispersals across the BLB ~875-625 and ~200-50 thousand years ago, during the Middle and Late Pleistocene. Whole genome analysis indicated low levels of gene flow between North American and Eurasian horse populations, which probably occurred as a result of these inferred dispersals. Nonetheless, mitochondrial and nuclear diversity of caballine horse populations retained strong phylogeographical structuring. Our results suggest that barriers to gene flow, currently unidentified but possibly related to habitat distribution across Beringia or ongoing evolutionary divergence, played an important role in shaping the early genetic history of caballine horses, including the ancestors of living horses within Equus ferus.
白令陆桥（BLB）在晚更新世时期最后一次连接了欧亚大陆和北美洲。尽管白令陆桥本可促成陆地生物群在两个方向上的迁移，但它也起到了生态过滤器的作用，其通透性随时间有很大变化。在此，我们探讨了这条生态走廊对曾经分布广泛的马属动物（Equus spp.）种群内部的遗传多样性以及种群间连通性可能产生的影响。我们使用了一组从全北区采集的现代和已灭绝马属动物样本中获得的187个线粒体基因组和8个核基因组，发现欧亚马种群最初在约100万至80万年前与它们的祖传大陆北美洲的马种群产生了分化。在这次分化之后，我们的线粒体DNA分析确定在中更新世和晚更新世期间，约87.5万至62.5万年前以及约20万至5万年前，有两次双向的长距离扩散跨越了白令陆桥。全基因组分析表明北美和欧亚马种群之间的基因流动水平较低，这可能是这些推断扩散的结果。尽管如此，马属动物种群的线粒体和核多样性仍保留着强烈的系统地理学结构。我们的结果表明，目前尚未明确但可能与白令地区的栖息地分布或正在进行的进化分化有关的基因流动障碍，在塑造马属动物的早期遗传历史中发挥了重要作用，包括现存野马（Equus ferus）的祖先。
