title: Evolution of the angiosperms: calibrating the family tree.
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.
authors.affiliation: Department of Botany, The Natural History Museum, Cromwell Road, London SW7 5BD, UK. N.Wikstrom@nhm.ac.uk
authors.forename: N
authors.initials: N
authors.lastname: Wikström
authors.forename: V
authors.initials: V
authors.lastname: Savolainen
authors.forename: M W
authors.initials: MW
authors.lastname: Chase
mesh_terms: D002138:Calibration; D019143:Evolution, Molecular; D019684:Magnoliopsida / Q000145:classification* / Q000235:genetics; D012337:RNA, Ribosomal, 18S; D012273:Ribulose-Bisphosphate Carboxylase / Q000235:genetics
chemical_list: D012337:RNA, Ribosomal, 18S; C101625:RbcL protein, plastid; D012273:Ribulose-Bisphosphate Carboxylase