title: Heterogeneous Rates of Molecular Evolution and Diversification Could Explain the Triassic Age Estimate for Angiosperms.
abstract: Dating analyses based on molecular data imply that crown angiosperms existed in the Triassic, long before their undisputed appearance in the fossil record in the Early Cretaceous. Following a re-analysis of the age of angiosperms using updated sequences and fossil calibrations, we use a series of simulations to explore the possibility that the older age estimates are a consequence of (i) major shifts in the rate of sequence evolution near the base of the angiosperms and/or (ii) the representative taxon sampling strategy employed in such studies. We show that both of these factors do tend to yield substantially older age estimates. These analyses do not prove that younger age estimates based on the fossil record are correct, but they do suggest caution in accepting the older age estimates obtained using current relaxed-clock methods. Although we have focused here on the angiosperms, we suspect that these results will shed light on dating discrepancies in other major clades.
authors.affiliation: National Institute for Mathematical and Biological Synthesis (NIMBioS); jbeaulieu@nimbios.org.
authors.forename: Jeremy M
authors.initials: JM
authors.lastname: Beaulieu
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Tennessee, Knoxville, TN 37996-1610, USA;
authors.forename: Brian C
authors.initials: BC
authors.lastname: O'Meara
authors.affiliation: School of Forestry and Environmental Studies, Yale University, 195 Prospect Street, New Haven, CT 06511, USA; and.
authors.forename: Peter
authors.initials: P
authors.lastname: Crane
authors.affiliation: Department of Ecology and Evolutionary Biology, Yale University, PO Box 208106, New Haven, CT 10620, USA.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Donoghue
mesh_terms: D003198:Computer Simulation; D019143:Evolution, Molecular; D005580:Fossils; D019684:Magnoliopsida / Q000145:classification* / Q000235:genetics*; D008957:Models, Genetic; D010802:Phylogeny; D013995:Time
keywords: Angiosperms; birth–death; divergence times; land plants; rates of molecular evolution