title: A multi-locus time-calibrated phylogeny of the brown algae (Heterokonta, Ochrophyta, Phaeophyceae): Investigating the evolutionary nature of the "brown algal crown radiation".
abstract: The most conspicuous feature in previous phaeophycean phylogenies is a large polytomy known as the brown algal crown radiation (BACR). The BACR encompasses 10 out of the 17 currently recognized brown algal orders. A recent study has been able to resolve a few nodes of the BACR, suggesting that it may be a soft polytomy caused by a lack of signal in molecular markers. The present work aims to refine relationships within the BACR and investigate the nature and timeframe of the diversification in question using a dual approach. A multi-marker phylogeny of the brown algae was built from 10 mitochondrial, plastid and nuclear loci (>10,000 nt) of 72 phaeophycean taxa, resulting in trees with well-resolved inter-ordinal relationships within the BACR. Using Bayesian relaxed molecular clock analysis, it is shown that the BACR is likely to represent a gradual diversification spanning most of the Lower Cretaceous rather than a sudden radiation. Non-molecular characters classically used in ordinal delimitation were mapped on the molecular topology to study their evolutionary history.
authors.affiliation: UMR 7138, UPMC, MNHN, CNRS, IRD: Systématique, adaptation, évolution, Département Systématique & évolution, USM 603, Muséum National d'Histoire Naturelle, 75231 Paris cedex 05, France. ilberfeld@mnhn.fr
authors.forename: Thomas
authors.initials: T
authors.lastname: Silberfeld
authors.forename: Jessica W
authors.initials: JW
authors.lastname: Leigh
authors.forename: Heroen
authors.initials: H
authors.lastname: Verbruggen
authors.forename: Corinne
authors.initials: C
authors.lastname: Cruaud
authors.forename: Bruno
authors.initials: B
authors.lastname: de Reviers
authors.forename: Florence
authors.initials: F
authors.lastname: Rousseau
mesh_terms: D001499:Bayes Theorem; D002467:Cell Nucleus / Q000235:genetics; D048028:DNA, Algal / Q000235:genetics; D004272:DNA, Mitochondrial / Q000235:genetics; D019143:Evolution, Molecular; D008957:Models, Genetic; D000459:Phaeophyceae / Q000145:classification / Q000235:genetics*; D010802:Phylogeny; D018087:Plastids / Q000235:genetics; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA
chemical_list: D048028:DNA, Algal; D004272:DNA, Mitochondrial