These observations would suggest the   possibility of using analyses of branch lengths on a DNA tree for explicit   tests of species boundaries, based on the difference in branching rates at   the level of species and populations. Branch lengths between species are   determined by speciation and extinction rates (macroevolution) (Nee et al.,   1994), whereas branch lengths within a species reflect coalescence processes   at the level of populations (microevolution) (Hudson, 1991; Rosenberg and   Nordborg, 2002; Wakeley, 2006). Well-developed approaches exist for analyzing   branching rates in either framework. Combining equations that describe processes   of lineage birth at the species level with coalescence models within species,   it is possible to develop a statistical framework for estimating the   predicted shift in dynamics of branching associated with the species   boundary. Here we develop a method that determines the locations of ancestral   nodes that define putative species and applies a likelihood ratio test to   assess the fit of the branch lengths to a mixed lineage birth-population   coalescence model.

这些观察结果表明，根据物种和种群水平上的分支速率差异，可以利用DNA树上的分支长度分析来明确探测物种边界。物种间的分支长度由物种形成和灭绝率（宏观进化）决定（Nee et al., 1994），而物种内的分支长度反映了种群水平上的溯祖过程（微观进化）（Hudson, 1991; Rosenberg and Nordborg, 2002; Wakeley, 2006）。在这两个框架中，都存在分析分支率的成熟方法。将描述物种层次上谱系产生过程的方程与物种内部的溯祖模型相结合，可以建立一个统计框架来估计与物种边界相关的分支动态变化。在这里，我们开发了一种方法，确定祖先节点的位置以定义推定物种，并应用似然率测试来评估分支长度匹配混合的谱系发生-种群溯祖模型的程度。