Biology:Supergroup

Short description: Classification rank for living beings

A supergroup, in evolutionary biology, is a large group of organisms that share one common ancestor and have important defining characteristics. It is an informal, mostly arbitrary rank in biological taxonomy that is often greater than phylum or kingdom, although some supergroups are also treated as phyla.

Eukaryotic supergroups

Since the decade of 2000's, the eukaryotic tree of life (abbreviated as eToL) has been divided into 5–8 major groupings called 'supergroups'. These groupings were established after the idea that only monophyletic groups should be accepted as ranks, as an alternative to the use of paraphyletic kingdom Protista. In the early days of the eToL six traditional supergroups were considered: Amoebozoa, Opisthokonta, "Excavata", Archaeplastida, "Chromalveolata" and Rhizaria. Since then, the eToL has been rearranged profoundly, and most of these groups were found as paraphyletic or lacked defining morphological characteristics that unite their members, which makes the 'supergroup' label more arbitrary.

Phylogenomic tree of eukaryotes, as regarded in 2020. Supergroups are in color.

Currently, the addition of many lineages of newly discovered protists (such as Telonemia, Picozoa, Hemimastigophora, Rigifilida...) and the use of phylogenomic analyses have brought a new, more accurate supergroup model. These are the current supergroups of eukaryotes:

• TSAR, constituted by Telonemia and the SAR clade (Stramenopiles, Alveolata and Rhizaria). It is estimated to occupy up to half of all eukaryotic diversity, since it includes multiple major groups such as diatoms, dinoflagellates, seaweeds, ciliates, foraminiferans, radiolarians, and the apicomplexan and oomycete parasites. It essentially contains the majority of "Chromalveolata".
• Haptista (also treated as a phylum), previously in "Chromalveolata", comprising the haptophyte algae and centrohelids.
• Cryptista (also treated as a phylum), previously in "Chromalveolata", comprising the cryptomonads, katablepharids and the enigmatic Palpitomonas.
• Archaeplastida (also treated as a kingdom), constituted by the lineages that acquired chloroplasts through primary endosymbiosis: Chloroplastida (green algae and land plants), Rhodophyta, Glaucophyta and Rhodelphis.
• Amorphea, composed by the Amoebozoa and the Opisthokonta (animals, fungi and related protists). They're related to the breviates and the apusomonads, and together form the clade Obazoa.
• CRuMs, composed by the free-living protozoan groups Collodictyonidae, Rigifilida and Mantamonas.
• Discoba, constituted by Discicristata (Euglenozoa and Heterolobosea), Jakobida and Tsukubamonas. It is the biggest remaining clade of the "Excavates".
• Metamonada, previously part of the "Excavates", entirely containing anaerobic protists.
• Hemimastigophora, previously an orphan clade but recently brought into Diaphoretickes.
• Provora, the most recent supergroup, containing the previously orphan Ancoracysta.

Many orphan groups of free-living protozoa remain left behind, unable to be added to a supergroup, such as: Picozoa (possibly belongs to Archaeplastida with limited certainty), Malawimonadida (thought to be related to Metamonada), Ancyromonadida, Breviatea, Apusomonadida, etc.

A possible modern topology of the eToL would be the following (supergroups labeled in bold):

Eukaryota	Diaphoretickes         TSAR 55px     Haptista       Provora       Hemimastigophora         Cryptista     Archaeplastida 50px         Discoba       Metamonada         Ancyromonadida       Malawimonadida       CRuMs     Amorphea 80px

Prokaryotic supergroups

The term 'supergroup' is used in phylogenetic studies of bacteria, in a more specific sense than within eukaryotes. As of 2021, it is very commonly used for naming clades within the genus Wolbachia.