Fig. 4.

Diagram of ancestral–descendent transitions among different latitudinal zones. Circles are proportional to the log of the number of lineages (nodes + tips) in each zone, and the pie sectors represent the fractional ancestry of descendent lineages in that zone (i.e., the fraction of transitions to that zone from each zone). The size of the arrows and the percentages represent the fraction of transitions from that zone to each zone. Thin dashed arrows represent only 1–4% of transitions out of the respective zones. Zones are defined by ranges of tropicality values: tropical (red): 0.5 ≤ TI ≤ 1.0, semitropical (dark red): 0 ≤ TI < 0.5, semitemperate (dark blue): −0.5 ≤ TI < 0, temperate (blue): −1 ≤ TI < −0.5.