Figure 1

Most parsimonious interpretations of phylogenetic hypotheses to identify the geographic origin of species. Shown are possible derivations of species from (a) Andean or (b) Amazonian ancestors. Determining the polarity of a biogeographic transition (T, inside box) requires a phylogeny with at least three in-group members and a well-supported outgroup rooting the tree. (c) If the outgroup is unknown or poorly supported, it is not possible to identify the geographic range of the stem ancestor from which the transition originated. Using Bayesian or maximum-likelihood frameworks for reconstructing ancestral ranges (e.g., in Lagrange [25]) incorporates this topological data along with information such as the distribution of branch lengths and the historical connectivity of regions.