In the examples in this paper, we fix p k~1 =K and d KL achieves its maximum log K when the posterior places all estimable mass on a single location. From this perspective, log K{d KL plays the role of a measure of dispersion [55] or uncertainty. As a simple numerical summary, we also use d KL to explore the utility of BSSVS and distance-informed priors on drawing inference from phylogeographic models. Larger values signify that the model extracts more information from the data. To calculate KL divergence, we employ a uniform discrete distribution as reference distribution. Association index. Following existing phylogeographic approaches, we finally score the degree of spatial admixture using a modified association index (AI) [35] . For a given phylogeny F and tip locations X, we obtain the association value d AI by summing over each internal node n,