主流分子钟定年方法的原理、误差来源和使用建议

陈旸康, 王益, 李家亮, 王文韬, 冯端宇, 毛康珊

Principles, error sources and application suggestions of prevailing molecular dating methods

Yangkang Chen, Yi Wang, Jialiang Li, Wentao Wang, Duanyu Feng, Kangshan Mao

图2 不同的分子钟模型示意图(改自: Ho & Duchêne, 2014)。图中的6个时间树具有相同的结构, 但由于分子钟模型选择的不同, 支长有很大差异。(a)未添加分子钟模型的时间树, 比例尺显示了1个时间单位。(b)严格分子钟模型, 所有支的速率相等。(c)局部多速率分子钟, 允许一定量的速率存在, 并根据拓扑的聚类情况设置速率, 同一类群具有相同或相似的速率。(d)离散多速率分子钟, 允许一定量的速率存在, 不考虑拓扑聚类情况的模型。(e)自相关松弛分子钟, 允许最多等于支数的速率存在, 且邻近支的速率相关。(f)非自相关松弛分子钟, 没有任何对速率的数量、分布格局的限制, 是最宽松自由的模型设置。

Fig. 2 Schematic diagram of different molecular clock models (modified from Ho & Duchêne, 2014). The six time trees in this figure have the same structure, but the branch length varies greatly due to different selection of molecular clock models. (a) The time tree without applying molecular clock model. The scale bar indicates one time unit. (b) In strict molecular clock model, all branches have the same rate. (c) Local multi-rate molecular clock allows a certain amount of rate and sets the rate according to the clustering situation of topology. The related branches have the same or similar rate. (d) Discrete multi-rate molecular clock, which also allows a certain amount of rate, does not consider the topological clustering. (e) The autocorrelated relaxed molecular clock allows the existence of a rate at most equal to the number of branches, and the rate dependence of adjacent branches. (f) The uncorrelated relaxed molecular clock, without any restrictions on the number and distribution pattern of rates, is the most relaxed and free model setting.