Figure 2

Prior and posterior distributions of the number of rate changes for three molecular data sets. Comparison of posterior (red) to prior (blue) probability mass functions of the number of rate changes K for the (a) mammal, (b) primate and (c) influenza examples. In all examples, the prior probability of a global molecular clock (K = 0) is 50%. Greater posterior than prior probability for K = 0 supports the global clock hypothesis (primates); while small or negligible posterior probability for K = 0 strongly rejects the hypothesis (mammals and influenza).