The Tree of Life Consolidates

Roland Piquepaille writes "The Tree of Life is an expression first used by Charles Darwin to describe the diversity of organisms on Earth and their evolutionary history. There are only two life forms, — eukaryotes, which gather their genetic material in a nucleus, and prokaryotes, such as bacteria, which have their genetic material floating freely in the cell. Until recently, eukaryotes, which include humans, were divided into five groups. But now, based on work by European researchers, the Tree of Life has lost a branch. After doing the largest ever genetic comparison of life forms they concluded that there are only four groups of eukaryotes."

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PLoS ONE: Phylogenomics Reshuffles the Eukaryotic

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Phylogenomics Reshuffles the Eukaryotic Supergroups

Fabien Burki1*, Kamran Shalchian-Tabrizi3, Marianne Minge3, Åsmund Skjæveland3, Sergey I. Nikolaev2, Kjetill S. Jakobsen3, Jan Pawlowski1

1 Department of Zoology and Animal Biology, University of Geneva, Geneva, Switzerland, 2 Department of Genetic Medicine and Development, University of Geneva, Geneva, Switzerland, 3 Department of Biology, University of Oslo, Oslo, Norway
Abstract
Background

Resolving the phylogenetic relationships between eukaryotes is an ongoing challenge of evolutionary biology. In recent years, the accumulation of molecular data led to a new evolutionary understanding, in which all eukaryotic diversity has been classified into five or six supergroups. Yet, the composition of these large assemblages and their relationships remain controversial.
Methodology/Principle Findings

Here, we report the sequencing of expressed sequence tags (ESTs) for two species belonging to the supergroup Rhizaria and present the analysis of a unique dataset combining 29908 amino acid positions and an extensive taxa sampling made of 49 mainly unicellular species representative of all supergroups. Our results show a very robust relationship between Rhizaria and two main clades of the supergroup chromalveolates: stramenopiles and alveolates. We confirm the existence of consistent affinities between assemblages that were thought to belong to different supergroups of eukaryotes, thus not sharing a close evolutionary history.
Conclusions

This well supported phylogeny has important consequences for our understanding of the evolutionary history of eukaryotes. In particular, it questions a single red algal origin of the chlorophyll-c containing plastids among the chromalveolates. We propose the abbreviated name 'SAR' (Stramenopiles+Alveolates+Rhizaria) to accommodate this new super assemblage of eukaryotes, which comprises the largest diversity of unicellular eukaryotes.

Citation: Burki F, Shalchian-Tabrizi K, Minge M, Skjæveland Å, Nikolaev SI, et al. (2007) Phylogenomics Reshuffles the Eukaryotic Supergroups. PLoS ONE 2(8): e790. doi:10.1371/journal.pone.0000790

Academic Editor: Geraldine Butler, University College Dublin, Ireland

Received: June 17, 2007; Accepted: July 26, 2007; Published: August 29, 2007

Copyright: © 2007 Burki et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Funding: This research was supported by the Swiss National Science Foundation grant 3100A0-100415 and 3100A0-112645 (JP); and by research grant (grant no 118894/431) from the Norwegian Research Council (KSJ).

Competing interests: The authors have declared that no competing interests exist.

* To whom correspondence should be addressed. E-mail: Fabien.Burki@zoo.unige.ch