Evolution of the angiosperms: calibrating the family tree

TLDR

Morphological diversity in angiosperm flowers, seeds, and pollen from the mid‑Cretaceous and derived lineages in older deposits suggest that early angiosperm diversification predates fossil estimates, prompting the use of DNA sequence divergence as an alternative calibration. Here, angiosperm divergence times are estimated using non‑parametric rate smoothing and a three‑gene dataset covering about 75 % of all angiosperm families, and an internal calibration point is used to independently evaluate angiosperm and eudicot origins. The study applies non‑parametric rate smoothing to a three‑gene dataset representing about 75 % of angiosperm families to estimate divergence times. The analysis indicates that the crown group of extant angiosperms originated in the Early to Middle Jurassic (179–158 Myr) and eudicots in the Late Jurassic to mid‑Cretaceous (147–131 Myr), both older than current fossil‑based estimates.

Abstract

Growing evidence of morphological diversity in angiosperm flowers, seeds and pollen from the mid Cretaceous and the presence of derived lineages from increasingly older geological deposits both imply that the timing of early angiosperm cladogenesis is older than fossil–based estimates have indicated. An alternative to fossils for calibrating the phylogeny comes from divergence in DNA sequence data. Here, angiosperm divergence times are estimated using non–parametric rate smoothing and a three–gene dataset covering ca. 75– of all angiosperm families recognized in recent classifications. The results provide an initial hypothesis of angiosperm diversification times. Using an internal calibration point, an independent evaluation of angiosperm and eudicot origins is performed. The origin of the crown group of extant angiosperms is indicated to be Early to Middle Jurassic (179–158 Myr), and the origin of eudicots is resolved as Late Jurassic to mid Cretaceous (147–131 Myr). Both estimates, despite a conservative calibration point, are older than current fossil–based estimates.