Accurate estimates of divergence times are essential to understand the evolutionary history of species. It allows linking evolutionary histories of the diverging lineages with past geological, climatic, and other changes in environment and shed light on the processes involved in speciation. The pea aphid radiation includes multiple host races adapted to different legume host plants. It is thought that diversification in this system occurred very recently, over the past 8,000–16,000 years. This young age estimate was used to link diversification in pea aphids to the onset of human agriculture, and led to the establishment of the pea aphid radiation as a model system in the study of speciation with gene flow. Here, we re-examine the age of the pea aphid radiation, by combining a mutation accumulation experiment with a genome-wide estimate of divergence between distantly related pea aphid host races. We estimate the spontaneous mutation rate for pea aphids as $2.7×10-10$ per haploid genome per parthenogenic generation. Using this estimate of mutation rate and the genome-wide genetic differentiation observed between pea aphid host races, we show that the pea aphid radiation is much more ancient than assumed previously, predating Neolithic agriculture by several hundreds of thousands of years. Our results rule out human agriculture as the driver of diversification of the pea aphid radiation, and call for re-assessment of the role of allopatric isolation during Pleistocene climatic oscillations in divergence of the pea aphid complex.

中文翻译：

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豌豆蚜虫的自发突变率和更新世辐射低。

准确估计发散时间对于了解物种的进化史至关重要。它允许将不同血统的进化历史与过去的地质，气候以及环境的其他变化联系起来，并阐明物种形成过程。豌豆蚜虫辐射包括适应不同豆类寄主植物的多个寄主种族。据认为，该系统的多样化是在最近的8,000-16,000年中发生的。这个年轻的年龄估计被用来将豌豆蚜虫的多样化与人类农业的开始联系起来，并导致了豌豆蚜虫辐射的建立，作为研究基因流形态的模型系统。在这里，我们重新检查豌豆蚜虫辐射的年龄，通过将突变积累实验与远距离相关的豌豆蚜虫宿主种族之间的差异的全基因组估计相结合。我们估计豌豆蚜虫的自发突变率为$2.7×10--10$每个单性生殖基因组的每个单倍体基因组。使用这种估计的突变率和豌豆蚜虫宿主种族之间观察到的全基因组遗传分化，我们证明了豌豆蚜虫的辐射远比以前假设的要古老，比新石器时代的农业要早几十万年。我们的结果排除了人类农业作为豌豆蚜虫辐射多样化的驱动力，并呼吁重新评估异新世隔离在豌豆蚜虫复杂性的更新世气候振荡过程中的作用。