A metacalibrated time-tree documents the early rise of flowering plant phylogenetic diversity

Abstract

The establishment of modern terrestrial life is indissociable from angiosperm evolution. While available molecular clock estimates of angiosperm age range from the Paleozoic to the Late Cretaceous, the fossil record is consistent with angiosperm diversification in the Early Cretaceous. The time-frame of angiosperm evolution is here estimated using a sample representing 87% of families and sequences of five plastid and nuclear markers, implementing penalized likelihood and Bayesian relaxed clocks. A literature-based review of the palaeontological record yielded calibrations for 137 phylogenetic nodes. The angiosperm crown age was bound within a confidence interval calculated with a method that considers the fossil record of the group. An Early Cretaceous crown angiosperm age was estimated with high confidence. Magnoliidae, Monocotyledoneae and Eudicotyledoneae diversified synchronously 135-130 million yr ago (Ma); Pentapetalae is 126-121 Ma; and Rosidae (123-115 Ma) preceded Asteridae (119-110 Ma). Family stem ages are continuously distributed between c. 140 and 20 Ma. This time-frame documents an early phylogenetic proliferation that led to the establishment of major angiosperm lineages, and the origin of over half of extant families, in the Cretaceous. While substantial amounts of angiosperm morphological and functional diversity have deep evolutionary roots, extant species richness was probably acquired later.

Keywords: calibrations; constraints; diversification; fossil record; maximum age; radiations; relaxed molecular clocks.