Figure 4.

Chronograms illustrating timing of lobeliad evolution based on (a) bottom-up calibration of the in-group molecular phylogeny against asterid fossils and (b) top-down calibration against ages of islands to which individual Hawaiian species are restricted; arrows indicate inferred times and places of initial colonization in the Hawaiian chain. Map shows extant tall islands (green) and submarine contours (blue) associated with original shorelines of islands that are now reduced to pinnacles or reefs in the northwest Hawaiian Islands. Current/former volcanoes are highlighted in red; dated volcanoes are highlighted by triangles. Bars represent ±1 s.d. for age estimates, based on bootstrapping of the in-group data (SD_b=grey) and variation across out-group trees in calibration set point(s) (SD_c=magenta). Total s.d.=(SD_b²+SD_c²)^0.5. SD_c falls monotonically towards the present, while SD_b first rises and then falls (see the electronic supplementary material).