Malawimonad

Malawimonads (order Malawimonadida) are a small group of microorganisms with a basal position in the evolutionary tree of eukaryotes, containing only three recognized species.[2] They're considered part of a possibly paraphyletic group known as "Excavata".[3][4]

Malawimonads
Light microscopy image of the malawimonad Gefionella okellyi
Scientific classification Edit this classification
Domain: Eukaryota
Phylum: Malawimonada
Cavalier-Smith 2021[1]
Class: Malawimonadea
Cavalier-Smith 2013
Order: Malawimonadida
Cavalier-Smith 2003
Families
Diversity[2]
3 species
Synonyms

Neolouka Cavalier-Smith 2013

Evolution

It is clear that the malawimonads are a monophyletic clade at the base of Eukaryota, but there is no consensus on the specific relationships between other basal groups, such as Discoba, Metamonada, Ancyromonadida and Podiata. The sister group to Malawimonadida varies greatly between analyses.[2] Some phylogenetic analyses find Malawimonadida as the sister group to Podiata.[5] Other analyses recover Malawimonadida as the sister group of Discoba or Metamonada. Very few modern analyses recover the three clades, Malawimonadida, Discoba and Metamonada, forming an unexpected monophyletic Excavata.[2]

Eukaryota

Diaphoretickes (plants, chromalveolates...)

Discoba

Jakobea

Tsukubea

Euglenozoa

Heterolobosea

Metamonada

Malawimonadida

Ancyromonadida

Podiata

CRuMs

Amorphea (amoebozoa, fungi, animals...)

Taxonomy

History

The malawimonads were first described as order Malawimonadida in 2003 by Thomas Cavalier-Smith. In 2013 they were also described as a class (Malawimonadea) and were placed as the only member of the subphylum Neolouka as part of the phylum "Loukozoa", a polyphyletic group uniting Metamonada, Jakobea, Tsukubea and the malawimonads.[6] Later, the Loukozoa broke apart and Neolouka was raised to the rank of phylum. Finally, this phylum containing only malawimonads was renamed in 2021 to Malawimonada by the same author, and was placed in a separate kingdom by the same name.[1]

Classification

Initially, Malawimonadida was a monotypic order, containing only the family Malawimonadidae and the genus Malawimonas. In 2018, the genus Gefionella was first described and added to this family. In 2020, a new genus Imasa and a new family Imasidae were added to the group. Presently, Malawimonadida contains 2 families, 3 genera and 3 accepted species:[2]

References
  1. Cavalier-Smith T (December 2021). "Ciliary transition zone evolution and the root of the eukaryote tree: implications for opisthokont origin and classification of kingdoms Protozoa, Plantae, and Fungi". Protoplasma. 259: 487–593. doi:10.1007/s00709-021-01665-7. PMC 9010356.
  2. Heiss AA, Warring SD, Lukacs K, Favate J, Yang A, Gyaltshen Y, Filardi C, Simpson AGB, Kim E (December 2020). "Description of Imasa heleensis, gen. nov., sp. nov. (Imasidae, fam. nov.), a Deep-Branching Marine Malawimonad and Possible Key Taxon in Understanding Early Eukaryotic Evolution". Journal of Eukaryotic Microbiology. 68: e12837. doi:10.1111/jeu.12837.
  3. Kolisko M, Flegontova O, Karnkowska A, Lax G, Maritz JM, Pánek T, Táborský P, Carlton JM, Čepička I, Aleš H, Julius L, Simpson AGB, Tai V (2020). "EukRef-excavates: seven curated SSU ribosomal RNA gene databases". Database. 2020 (baaa080). doi:10.1093/database/baaa080. PMC 7678783.
  4. Heiss, Aaron A.; Kolisko, Martin; Ekelund, Fleming; Brown, Matthew W.; Roger, Andrew J.; Simpson, Alastair G. B.; et al. (2018). "Combined morphological and phylogenomic re-examination of malawimonads, a critical taxon for inferring the evolutionary history of eukaryotes". Royal Society Open Science. 5 (4): 171707. Bibcode:2018RSOS....571707H. doi:10.1098/rsos.171707. PMC 5936906. PMID 29765641.
  5. Brown MW, et al. (2018), "Phylogenomics Places Orphan Protistan Lineages in a Novel Eukaryotic Super-Group", Genome Biology and Evolution, 10 (2): 427–433, doi:10.1093/gbe/evy014, PMC 5793813
  6. Cavalier-Smith, Thomas (2013-05-01). "Early evolution of eukaryote feeding modes, cell structural diversity, and classification of the protozoan phyla Loukozoa, Sulcozoa, and Choanozoa". European Journal of Protistology. 49 (2): 115–178. doi:10.1016/j.ejop.2012.06.001. PMID 23085100.
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