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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >The timing of eukaryotic evolution: does a relaxed molecular clock reconcile proteins and fossils?
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The timing of eukaryotic evolution: does a relaxed molecular clock reconcile proteins and fossils?

机译：真核生物进化的时机：宽松的分子钟能调节蛋白质和化石吗？

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摘要

The use of nucleotide and amino acid sequences allows improved understanding of the timing of evolutionary events of life on earth. Molecular estimates of divergence times are, however, controversial and are generally much more ancient than suggested by the fossil record. The limited number of genes and species explored and pervasive variations in evolutionary rates are the most likely sources of such discrepancies. Here we compared concatenated amino acid sequences of 129 proteins from 36 eukaryotes to determine the divergence times of several major clades, including animals, fungi, plants, and various protists. Due to significant variations in their evolutionary rates, and to handle the uncertainty of the fossil record, we used a Bayesian relaxed molecular clock simultaneously calibrated by six paleontological constraints. We show that, according to 95% credibility intervals, the eukaryotic kingdoms diversified 950-1,259 million years ago (Mya), animals diverged from choanoflagellates 761-957 Mya, and the debated age of the split between protostomes and deuterostomes occurred 642-761 Mya. The divergence times appeared to be robust with respect to prior assumptions and paleontological calibrations. Interestingly, these relaxed clock time estimates are much more recent than those obtained under the assumption of a global molecular clock, yet bilaterian diversification appears to be approximately 100 million years more ancient than the Cambrian boundary.
机译：核苷酸和氨基酸序列的使用允许更好地理解地球上生命的进化事件的时间。然而，发散时间的分子估计是有争议的，并且通常比化石记录所暗示的更古老。探究的基因和物种数量有限以及进化速率的普遍变化是此类差异的最可能来源。在这里，我们比较了来自36个真核生物的129种蛋白质的串联氨基酸序列，以确定几种主要进化枝（包括动物，真菌，植物和各种原生生物）的发散时间。由于它们进化速度的显着变化，并且要处理化石记录的不确定性，我们使用了贝叶斯松弛分子钟，该钟同时通过六个古生物学约束条件进行了校准。我们证明，按照95％的可信度区间，真核生物王国在950-1,259百万年前（Mya）发生了分化，动物从鞭毛鞭毛虫761-957 Mya分化，并且原虫和氘核之间分裂的辩论年龄发生了642-761 Mya 。相对于先前的假设和古生物学标定，发散时间似乎很稳健。有趣的是，这些宽松的时钟时间估计比在全球分子时钟假设下获得的估计时间要新得多，但双边的多样化似乎比寒武纪边界古老了大约一亿年。

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