Figure 3.

Dating the origin of Chrysomelidae under various absolute age calibrations. (a) Linearized tree with branch lengths proportional to substitution rate used to estimate the age of the Chrysomelidae. The uncertainty of fossil placements along the branches leading to a dated crown group is represented by the intervals (1, 2) (white: sagrine-like fossil; black: hispine-like feeding traces); the biogeographical event (“B” in gray circle) represents a maximum age for the vicariant split. Black triangles along branches represent the approximate placement of fossils known for each leaf beetle subfamily (all Eocenic or younger; Quaternary fossils excluded). (b) Inferred ages and 94% confidence intervals for the Chrysomelidae. The origin of Chrysomelidae is defined by the first separation of basal lineages within the Chrysomelidae (minimum age; gray square) and the node separating Chrysomelidae from other Chrysomeloidea (maximum age; black square). These node ages (y-axis) were estimated with each of the three calibration points from dated fossils and biogeography. The precise age of the calibration points (x-axis) is affected by uncertainty regarding their placement along the branch defining the crown group, bracketed by the interval (1, 2), and therefore a range of dates on the y-axis (origin of Chrysomelidae) is given for the upper and lower bounds of the calibrations. These calibration points each have a confidence interval from character resampling shown by error bars. The tree in (a) was scaled to match the minimum possible root age according to the analysis in (b), i.e. the lower boundary of the confidence interval using the biogeographical calibration.