是否存在星树悖论?
Is there a star tree paradox?
作者信息
Kolaczkowski Bryan, Thornton Joseph W
出版信息
Mol Biol Evol. 2006 Oct;23(10):1819-23. doi: 10.1093/molbev/msl059. Epub 2006 Jul 12.
Concerns have been raised that posterior probabilities on phylogenetic trees can be unreliable when the true tree is unresolved or has very short internal branches, because existing methods for Bayesian phylogenetic analysis do not explicitly evaluate unresolved trees. Two recent papers have proposed that evaluating only resolved trees results in a "star tree paradox": when the true tree is unresolved or close to it, posterior probabilities were predicted to become increasingly unpredictable as sequence length grows, resulting in inflated confidence in one resolved tree or another and an increasing risk of false-positive inferences. Here we show that this is not the case; existing Bayesian methods do not lead to an inflation of statistical confidence, provided the evolutionary model is correct and uninformative priors are assumed. Posterior probabilities do not become increasingly unpredictable with increasing sequence length, and they exhibit conservative type I error rates, leading to a low rate of false-positive inferences. With infinite data, posterior probabilities give equal support for all resolved trees, and the rate of false inferences falls to zero. We conclude that there is no star tree paradox caused by not sampling unresolved trees.
有人担心,当真实树未解决或内部分支非常短时,系统发育树上的后验概率可能不可靠,因为现有的贝叶斯系统发育分析方法没有明确评估未解决的树。最近的两篇论文提出,仅评估已解决的树会导致“星树悖论”:当真实树未解决或接近未解决时,随着序列长度的增加,后验概率预计会变得越来越不可预测,从而导致对某一已解决树的信心膨胀以及假阳性推断的风险增加。在这里,我们表明情况并非如此;只要进化模型正确且假设使用无信息先验,现有的贝叶斯方法不会导致统计置信度的膨胀。后验概率不会随着序列长度的增加而变得越来越不可预测,并且它们表现出保守的I型错误率,导致假阳性推断的发生率较低。在有无限数据的情况下,后验概率对所有已解决的树给予同等支持,并且错误推断的发生率降至零。我们得出结论,不存在因未对未解决的树进行采样而导致的星树悖论。