where c n counts the number of sampled locations descendent to n and f n is the frequency of the highest frequency location amongst these descendents. Similar to [10] , we report the posterior distributions Pr d AI jX, Y ð Þ and the AI compares these distributions to those obtained by random permutation of the tip locations X. Deviation from these permuted distributions reflected in low AI values suggests phylogeographic structure whereas AI values close to 1 suggest spatial admixture.