School of Earth Sciences, University of Bristol, Bristol, UK.
Biol Lett. 2012 Feb 23;8(1):156-9. doi: 10.1098/rsbl.2011.0710. Epub 2011 Aug 24.
Calibration is a critical step in every molecular clock analysis but it has been the least considered. Bayesian approaches to divergence time estimation make it possible to incorporate the uncertainty in the degree to which fossil evidence approximates the true time of divergence. We explored the impact of different approaches in expressing this relationship, using arthropod phylogeny as an example for which we established novel calibrations. We demonstrate that the parameters distinguishing calibration densities have a major impact upon the prior and posterior of the divergence times, and it is critically important that users evaluate the joint prior distribution of divergence times used by their dating programmes. We illustrate a procedure for deriving calibration densities in Bayesian divergence dating through the use of soft maximum constraints.
校准是每个分子钟分析中至关重要的一步，但也是最被忽视的一步。贝叶斯方法在分歧时间估计中使得能够将化石证据与真实分歧时间的近似程度的不确定性纳入其中。我们使用节肢动物系统发育作为示例，探索了表达这种关系的不同方法的影响，为此我们建立了新的校准方法。我们证明了区分校准密度的参数对分歧时间的先验和后验有重大影响，因此用户评估其约会程序使用的分歧时间联合先验分布是至关重要的。我们通过使用软最大约束来演示在贝叶斯分歧时间约会中推导校准密度的过程。
