Figure 6.

Age and polarity of biogeographic transitions among the Andes and Amazon in other tropical lineages. A literature search of mammal, bird, amphibian, and insect lineages finds 87 dated transitions with identifiable polarities (listed in Table 5), including 35 with origins in the Andes and 52 that originated in the Amazon. Ages of transition are grouped in 1 Ma bins and their frequency is plotted by polarity. No significant trend in timing and polarity is observed, with considerable overlap in the distribution of Andes-to-Amazon ages (dark green; mean: 5.87, 95% confidence interval [CI]: 4.12, 7.62) and Amazon-to-Andes ages (light green; mean: 4.59, 95% CI: 3.55, 5.64). We plotted midpoints for ages with date ranges, values of 0.5 Ma for ages of < 1 Ma, and did not include transitions from undated phylogenies. Relevant geologic events are shown at the bottom and additional details are provided in the Discussion.