Co-Innovation Center for Sustainable Forestry in Southern China, College of Biology and the Environment, Key Laboratory of State Forestry and Grassland Administration on Subtropical Forest Biodiversity Conservation, Nanjing Forestry University, Nanjing, Jiangsu 210037, China.
Laboratory of Biodiversity and Conservation, College of Biology and the Environment, Nanjing Forestry University, Nanjing, Jiangsu 210037, China.
Ann Bot. 2022 Jan 28;129(2):231-245. doi: 10.1093/aob/mcab140.
Contemporary patterns of genetic admixture reflect imprints of both ancient and recent gene flow, which can provide us with valuable information on hybridization history in response to palaeoclimate change. Here, we examine the relationships between present admixture patterns and past climatic niche suitability of two East Asian Cerris oaks (Quercus acutissima and Q. chenii) to test the hypothesis that the mid-Pliocene warm climate promoted while the Pleistocene cool climate limited hybridization among local closely related taxa.
We analyse genetic variation at seven nuclear microsatellites (1111 individuals) and three chloroplast intergenic spacers (576 individuals) to determine the present admixture pattern and ancient hybridization history. We apply an information-theoretic model selection approach to explore the associations of genetic admixture degree with past climatic niche suitability at multiple spatial scales.
More than 70 % of the hybrids determined by Bayesian clustering analysis and more than 90 % of the individuals with locally shared chloroplast haplotypes are concentrated within a mid-Pliocene contact zone between ~30°N and 35°N. Climatic niche suitabilities for Q. chenii during the mid-Pliocene Warm Period [mPWP, ~3.264-3.025 million years ago (mya)] and during the Last Glacial Maximum (LGM, ~0.022 mya) best explain the admixture patterns across all Q. acutissima populations and across those within the ancient contact zone, respectively.
Our results highlight that palaeoclimate change shapes present admixture patterns by influencing the extent of historical range overlap. Specifically, the mid-Pliocene warm climate promoted ancient contact, allowing widespread hybridization throughout central China. In contrast, the Pleistocene cool climate caused the local extinction of Q. chenii, reducing the probability of interspecific gene flow in most areas except those sites having a high level of ecological stability.
当代的基因混合模式反映了古代和近期基因流动的印记，这为我们提供了有关杂交历史的宝贵信息，以应对古气候变化。在这里，我们研究了两个东亚赤松栎（Quercus acutissima 和 Q. chenii）的现代混合模式与过去气候生态位适宜性之间的关系，以检验这样一个假设，即中更新世暖期促进了局部亲缘种间的杂交，而更新世冷期则限制了这种杂交。
我们分析了七个核微卫星（1111 个个体）和三个叶绿体基因间区（576 个个体）的遗传变异，以确定现代混合模式和古代杂交历史。我们应用信息理论模型选择方法来探索遗传混合程度与多个空间尺度上过去气候生态位适宜性的关联。
贝叶斯聚类分析确定的杂交种超过 70%，具有局部共享叶绿体单倍型的个体超过 90%，集中在 30°N 至 35°N 之间的中更新世接触带内。中更新世暖期（mPWP，约 326.4-302.5 万年前）和末次冰期（LGM，约 0.022 万年前）的 Q. chenii 气候生态位适宜性分别最好地解释了所有 Q. acutissima 种群和古老接触带内种群的混合模式。
我们的结果强调，古气候变化通过影响历史分布范围的重叠程度来塑造现代混合模式。具体来说，中更新世暖期促进了古代接触，允许在中国中部广泛杂交。相比之下，更新世冷期导致 Q. chenii 在大多数地区局部灭绝，降低了除具有高生态稳定性的地点以外的大多数地区种间基因流动的可能性。
