Example to illustrate the concept of normalized weight (or probability) of ancestral assignments.

We present a simplified situation of two species related through a common ancestor, where the evolutionary tree has just one internal node representing the ancestor, with four possible ancestral assignments. For a sample PWM with 5 sites aligned over the two species, we provide representative values (in blue) for the probability of the tree corresponding to each site given a particular ancestral assignment. From these we work out the overall probability of an ancestral assignment given the data (last column). For details, see the text in the Materials and Methods section that references this table.

我们构建了一个由共同祖先演化而来的双物种类比简化场景：该演化树仅含一个代表该共同祖先的内部节点，且存在四种可能的祖先分配方案。针对在两个物种上比对得到的含5个位点的示例位置权重矩阵（Position Weight Matrix, PWM），我们给出了在特定祖先分配方案下，各对应位点匹配该演化树的概率代表性数值（以蓝色标注）。基于上述数值，我们可计算得到给定观测数据时各祖先分配方案的整体概率（详见最后一列）。欲了解详细信息，请参阅本文材料与方法部分中引用本表的相关内容。