Pleistocene glacial cycles influenced the diversification of high-latitude wildlife species through recurrent periods of range contraction, isolation, divergence, and expansion from refugia and subsequent admixture of refugial populations. We investigate population size changes and the introgressive history of caribou (Rangifer tarandus) in western Canada using 33 whole genome sequences coupled with larger-scale mitochondrial data. We found that a major population expansion of caribou occurred starting around 110,000 years ago (kya), the start of the last glacial period. Additionally, we found effective population sizes of some caribou reaching ~700,000 to 1,000,000 individuals, one of the highest recorded historical effective population sizes for any mammal species thus far. Mitochondrial analyses dated introgression events prior to the LGM dating to 20–30 kya and even more ancient at 60 kya, coinciding with colder periods with extensive ice coverage, further demonstrating the importance of glacial cycles and events prior to the LGM in shaping demographic history. Reconstructing the origins and differential introgressive history has implications for predictions on species responses under climate change. Our results have implications for other whole genome analyses using pairwise sequentially Markovian coalescent (PSMC) analyses, as well as highlighting the need to investigate pre-LGM demographic patterns to fully reconstruct the origin of species diversity, especially for high-latitude species.

中文翻译：

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末次盛冰期前冰川周期塑造的驯鹿种群动态

更新世冰川周期通过反复出现的范围收缩、隔离、分歧和从避难所扩张以及随后的避难种群混合，影响了高纬度野生动物物种的多样化。我们调查了北美驯鹿的种群规模变化和渐渗历史（Rangifer tarandus) 在加拿大西部使用 33 个全基因组序列和更大规模的线粒体数据。我们发现驯鹿的大规模人口扩张发生在大约 110,000 年前（kya），即最后一个冰期的开始。此外，我们发现一些驯鹿的有效种群规模达到了约 700,000 到 1,000,000 只个体，这是迄今为止任何哺乳动物物种中记录的最高历史有效种群规模之一。线粒体分析表明，LGM 之前的基因渗入事件可追溯到 20-30 kya 甚至更古老的 60 kya，与较冷的时期相吻合，冰覆盖范围广，进一步证明了 LGM 之前的冰川周期和事件在塑造人口历史方面的重要性。重建起源和不同的渐渗历史对预测气候变化下的物种反应具有重要意义。我们的结果对使用成对顺序马尔可夫聚结 (PSMC) 分析的其他全基因组分析具有影响，并强调需要研究 LGM 前的人口模式以完全重建物种多样性的起源，特别是对于高纬度物种。