The Relationship between γ and Clade Size and Age from Pure Birth Simulations

Plot of the γ statistic versus (A) clade size and (B) clade age in 10,000 simulated datasets of the pure birth model. Clade size simulations were run for 18 time units and clade age simulations were run until clades contained 50 species (both using a birth rate of 0.2). The solid line illustrates the relationship between γ and (A) clade size and (B) clade age, fitted using a cubic smoothing spline to capture non-linearity.