A multi-locus time-calibrated phylogeny of the brown algae (Heterokonta, Ochrophyta, Phaeophyceae): Investigating the evolutionary nature of the "brown algal crown radiation"

Mol Phylogenet Evol. 2010 Aug;56(2):659-74. doi: 10.1016/j.ympev.2010.04.020. Epub 2010 Apr 19.

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.

MeSH terms

  • Bayes Theorem
  • Cell Nucleus / genetics
  • DNA, Algal / genetics
  • DNA, Mitochondrial / genetics
  • Evolution, Molecular*
  • Models, Genetic
  • Phaeophyta / classification
  • Phaeophyta / genetics*
  • Phylogeny*
  • Plastids / genetics
  • Sequence Alignment
  • Sequence Analysis, DNA

Substances

  • DNA, Algal
  • DNA, Mitochondrial