Unravelling the Protists!

Decades ago in university, we used interesting names for many microscopic organisms and hadn’t names for many. Relationships were guessed at but mostly we were unsure of it all.

Well, biologists started out putting anything that wasn’t an animal, plant into a cabinet of curiosities called the Protists. By the time I was was an undergrad, we had settled for a five kingdom arrangement which included Kingdom Protista – it held anything which was not an animal, plant, fungi or bacteria.

A revolution of molecular information and imaging technology over the past decade or so led to an explosion in the tree of life which has better placed these microbial entities.

Just a couple of weeks ago, I used these supergroups to describe the lot – Unikonts (includes animals and fungi), Archaeplastids (plants, red/green algae), Rhizarians, Chromalveolates and Excavates (see Tree of Life).

Changes were promised and last week (28 Sep 2012), the International Society of Protistologists published “The Revised Classification of Eukaryotes” (free download) and the tree looks like this now:

The Revised Classification of Eukaryotes 2012 (page 4 of 79)

We were chatting about all this recently during a Lee Kong Chian Natural History Museum gallery design meeting and this morning, Rudolf Meier alerted me about this paper.

The authors reduced several paraphyletic and polyphyletic groups and say (amongst other things):

  • “Chromalveolates are probably polyphyletic”, so that show was blown.
  • Stramenopiles, Alveolates, and Rhizaria are clustered into SAR (apparently common usage).
  • Since “Unikonta” is misleading, it’s dropped but the grouping of Amoebozoa with Opisthokonta is recognised and a new taxon is coined for the super-duper group, the Amorphea.
  • The other super-duper group is Diaphoretickes. Yes, we’ll enjoy saying that.
  • An “Incertae sedis” bin holds uncertain groups.

So now eukaryotes are represented by these supergroups:

  • Sar
  • Archaeplastida
  • Excavata
  • Amoebozoa
  • Opisthokonta

The protistologists really took pains to communicate this news to ensure it is better reflected in new textbooks: the paper is free, it has a pretty, coloured tree and they say “Unlike a phylogenetic tree that tries to reflect correctly the relatedness of lineages, a classification has a utilitarian purpose of categorizing diversity in a practical manner. Thus, we have resisted in this classification creating ranks that were not necessary.”


And the best part, they agree to disagree – “While these individuals [the 25 authors] share authorship of this work, this does not mean that all the authors endorse every aspect of the proposed classification.”

Nice going, people! Until next time.

Ernst Haeckel would’ve loved this!

Mr Bats on Eagle's Nest
Metazoan connections are stable.

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