title: Do orthologous gene phylogenies really support tree-thinking?
abstract: BACKGROUND
  Since Darwin's Origin of Species, reconstructing the Tree of Life has been a goal of evolutionists, and tree-thinking has become a major concept of evolutionary biology. Practically, building the Tree of Life has proven to be tedious. Too few morphological characters are useful for conducting conclusive phylogenetic analyses at the highest taxonomic level. Consequently, molecular sequences (genes, proteins, and genomes) likely constitute the only useful characters for constructing a phylogeny of all life. For this reason, tree-makers expect a lot from gene comparisons. The simultaneous study of the largest number of molecular markers possible is sometimes considered to be one of the best solutions in reconstructing the genealogy of organisms. This conclusion is a direct consequence of tree-thinking: if gene inheritance conforms to a tree-like model of evolution, sampling more of these molecules will provide enough phylogenetic signal to build the Tree of Life. The selection of congruent markers is thus a fundamental step in simultaneous analysis of many genes.
  
  
  RESULTS
  Heat map analyses were used to investigate the congruence of orthologues in four datasets (archaeal, bacterial, eukaryotic and alpha-proteobacterial). We conclude that we simply cannot determine if a large portion of the genes have a common history. In addition, none of these datasets can be considered free of lateral gene transfer.
  
  
  CONCLUSIONS
  Our phylogenetic analyses do not support tree-thinking. These results have important conceptual and practical implications. We argue that representations other than a tree should be investigated in this case because a non-critical concatenation of markers could be highly misleading.
authors.affiliation: GenomeAtlantic, 1721 Lower Water Street, Suite 401, Halifax, NS, B3J 1S5, Canada. eric.bapteste@dal.ca
authors.forename: E
authors.initials: E
authors.lastname: Bapteste
authors.forename: E
authors.initials: E
authors.lastname: Susko
authors.forename: J
authors.initials: J
authors.lastname: Leigh
authors.forename: D
authors.initials: D
authors.lastname: MacLeod
authors.forename: R L
authors.initials: RL
authors.lastname: Charlebois
authors.forename: W F
authors.initials: WF
authors.lastname: Doolittle
mesh_terms: D000465:Algorithms; D020561:Alphaproteobacteria / Q000235:genetics; D000818:Animals; D005075:Biological Evolution; D019143:Evolution, Molecular; D022761:Gene Transfer, Horizontal; D019766:Genes, Archaeal; D005798:Genes, Bacterial; D005819:Genetic Markers; D016678:Genome; D008954:Models, Biological; D008957:Models, Genetic; D015233:Models, Statistical; D008962:Models, Theoretical; D010802:Phylogeny; D012984:Software
chemical_list: D005819:Genetic Markers