A new universal tree of life

A revised universal tree of life

A revised universal tree of life

Here’s a new depiction of the ‘universal evolutionary tree of life’ which incorporates some recent advances in the field. In particular, some fast-evolving taxa that are known spuriously placed in previous ribosomal RNA trees have been omitted (e.g. microsporidia, which are known to fall within the fungi), and it also illustrates the increasingly popular idea that Eukaryotes nest within the Archaea. Unlike some other universal trees on the internet, this is shown as an unrooted tree, which is a more conservative approach than the (arguable) rooting of the tree of life between Eubacteria and Archaea. The tree has the distinct advantage that it (more or less) correctly reflects our understanding of the major groups of Eukaryotes (including plants, fungi & animals). In my opinion it is a more accurate depiction of our state of knowledge than other ‘universal trees of life’ commonly found on the internet.

My tree is simply a visualisation of data from using the ARB software package. This study using ribosomal proteins rather than (just) small subunit ribosomal RNA. I place my visualisation in the public domain (although if anyone else uses this picture it would be polite to mention the original paper from which the data is taken)

A few more things to note:

  1. Substantial horizontal gene transfer is likely to mean that this tree only applies to a minority of genes in the genome. The hope is that it reflects the ‘core’ history of ancestral cell division.
  2. The tree is from the CAT analysis of , which specifically looks at amino acid sequences (hence rRNA is excluded). As they say, “In particular, CAT seemed to amalgamate the best features of other models – recovering clades 1 and 2 of Bacteria and major eukaryotic supergroups.”
  3. The multiple branches at the base of the Archaea are probably artifactual, and the branching order with Archaea is debatable. Further resolution is provided by . There is still argument about whether Archaea are monophyletic (associated with the old 3 domains view of life, see ), or if Eukaryotes nest within them (a more recent suggestion, badlyaBad because it is unclear where the root of the entire tree lies anyway dubbed the “2 domains” hypothesis, ).
  4. The Eubacterial branching pattern is difficult to resolve.
  5. There are a few recent discoveries that are not included, in particular the Eubacterial groups in the “candidate phyla radiation”  and the recently discovered Lokiarchaeota .

An Inkscape-compatible SVG file is available here.

Notes   [ + ]

a. Bad because it is unclear where the root of the entire tree lies anyway

Leave a Reply

Your email address will not be published. Required fields are marked *