Uncertainty in the Timing of Origin of Animals and the Limits of Precision in Molecular Timescales.
Uncertainty in the Timing of Origin of Animals and the Limits of Precision in Molecular Timescales.
复制标题
DOI：
10.1016/j.cub.2015.09.066
复制
发表时间：
2015-11-16
期刊：
影响因子：
--
通讯作者：
Yang Z
中科院分区：
文献类型：
--
作者：
dos Reis M;Thawornwattana Y;Angelis K;Telford MJ;Donoghue PC;Yang Z
后生动物谱系之间分歧的时间是理解动物进化过程的组成部分，将物种分歧的生物事件置于正确的地质时间框架中。最近的化石发现和分子钟测年研究表明，在寒武纪之前的1亿年左右左右，就已经出现了两侧生动物门的分歧，当时出现了第一个明确的冠状两侧生动物化石。然而，大多数以前的分子钟测年研究都受到数据有限和方法偏差的影响，几乎所有的研究都没有承认与早期动物化石记录相关的巨大不确定性，导致研究之间的估计不一致。在这里，我们使用了前所未有的分子数据量，结合四个化石校准策略（反映不同的和有争议的解释后生动物化石记录），以获得贝叶斯估计后生动物的分歧时间。我们的研究结果表明，古代化石的不确定性和违反分子钟施加的精度，可以实现在估计古代分子时标的限制。例如，虽然我们可以断言冠后生动物起源于低温期（大多数冠两侧门在埃迪卡拉纪期间多样化），但根据目前的数据，不可能以足够的准确度来确定分歧事件，以测试动物历史中地质和生物事件之间的相关性。虽然冠后生动物的低温起源同意目前的地质解释，分歧日期的bilaterians仍然存在争议。因此，试图建立基于分子钟时间尺度的早期动物进化的进化叙事似乎还为时过早。分子钟分析表明，动物的古老起源在低温纪动物门的多样化发生在埃迪卡拉纪，在寒武纪化石记录和分子钟影响时间估计之前，动物进化的精确时间轴不能用目前的方法获得dos Reis等人。研究贝叶斯估计的不确定性的时间起源的动物使用的基因组数据。他们发现，由于与早期动物化石记录相关的巨大不确定性以及古代生物进化中分子钟的强烈违反，解开早期动物进化的时间轴是困难的。
The timing of divergences among metazoan lineages is integral to understanding the processes of animal evolution, placing the biological events of species divergences into the correct geological timeframe. Recent fossil discoveries and molecular clock dating studies have suggested a divergence of bilaterian phyla >100 million years before the Cambrian, when the first definite crown-bilaterian fossils occur. Most previous molecular clock dating studies, however, have suffered from limited data and biases in methodologies, and virtually all have failed to acknowledge the large uncertainties associated with the fossil record of early animals, leading to inconsistent estimates among studies. Here we use an unprecedented amount of molecular data, combined with four fossil calibration strategies (reflecting disparate and controversial interpretations of the metazoan fossil record) to obtain Bayesian estimates of metazoan divergence times. Our results indicate that the uncertain nature of ancient fossils and violations of the molecular clock impose a limit on the precision that can be achieved in estimates of ancient molecular timescales. For example, although we can assert that crown Metazoa originated during the Cryogenian (with most crown-bilaterian phyla diversifying during the Ediacaran), it is not possible with current data to pinpoint the divergence events with sufficient accuracy to test for correlations between geological and biological events in the history of animals. Although a Cryogenian origin of crown Metazoa agrees with current geological interpretations, the divergence dates of the bilaterians remain controversial. Thus, attempts to build evolutionary narratives of early animal evolution based on molecular clock timescales appear to be premature. Molecular clock analysis indicates an ancient origin of animals in the Cryogenian Diversification into animal phyla occurred in the Ediacaran, before the Cambrian Uncertainties in the fossil record and the molecular clock affect time estimates A precise timeline of animal evolution cannot be obtained with current methods dos Reis et al. study the uncertainty in Bayesian estimates of the time of origin of animals using phylogenomic data. They find that disentangling the timeline of early animal evolution is hard given the large uncertainty associated with the fossil record of early animals and the strong violation of the molecular clock in ancient phylogenies.