Representation and Incorporation of Fossil Data in Molecular Dating of Species Divergences

如果我们的基因随着时间以恒定的速率积累变化，那么两个物种之间的遗传距离（以积累的变化数量来衡量）将与物种分歧的时间成正比。因此，分子可以作为一个时钟，通过累积的变化来保持物种分化的时间。如果化石记录或地质事件可以用来为系统发育树上的物种分歧事件分配绝对地质时间，那么可以将所有计算的遗传距离转换为绝对地质时间。分子钟测年的原理最近被扩展到处理进化速率的局部变化。分子测年的关键是使用化石信息来校准时钟。在这个项目中，我们将开发统计模型和计算机算法，以准确地表示和纳入分子测年分析中的化石校准信息。我们还将实现明确考虑化石校准错误的模型。新方法将被应用于分析大型序列数据集，以估计灵长类动物和脊椎动物之间的分歧时间。

If our genes accumulate changes over time at a constant rate, the genetic distance between two species, measured by the number of changes accumulated, will be proportional to the time of species divergence. Thus molecules can serve as a clock, keeping time of species divergence by the accumulated changes. If fossil records or geological events can be used to assign an absolute geological time to a species divergence event on the phylogenetic tree, one can convert all calculated genetic distances into absolute geological times. This rationale for molecular clock dating has recently been extended to deal with local variation in evolutionary rate. Critical to molecular dating is the use of fossil information to calibrate the clock. In this project, we will develop statistical models and computer algorithms to accurately represent and incorporate fossil calibration information in molecular dating analysis. We will also implement models that explicitly consider errors in fossil calibrations. The new methods will be applied to analyze large sequence datasets to estimate divergence times among primates and vertebrates.