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. 2014 Jul 28;111(32):11756–11761. doi: 10.1073/pnas.1411601111

Fig. 1.

Fig. 1.

Cumulative distribution of nodes uniting African and Oriental clades as a function of age. The data were fit by nonlinear regression (SAS Proc NLIN) to a model in which the cumulative number of clades exponentially approaches an asymptotic number of sister lineage pairs equal to the ratio of the colonization (C) and extinction (E) rate. The rank reaches 1/2 C/E when (1 – exp(−E*age)) = 0.5 or exp(−E*age) = 0.5, which, for E = 0.0798, occurs at 8.7 Ma. The Inset shows the distribution of the ages of nodes uniting sister taxa of African and Oriental passerine clades, grouped in four Ma intervals, with node rank indicated.