Malawimonads (order Malawimonadida) are a small group of

microorganism A microorganism, or microbe, is an organism of microscopic scale, microscopic size, which may exist in its unicellular organism, single-celled form or as a Colony (biology)#Microbial colonies, colony of cells. The possible existence of unseen ...

s with a basal position in the evolutionary tree of

eukaryotes The eukaryotes ( ) constitute the domain of Eukaryota or Eukarya, organisms whose cells have a membrane-bound nucleus. All animals, plants, fungi, seaweeds, and many unicellular organisms are eukaryotes. They constitute a major group of ...

, containing only three recognized

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

. They're considered part of a

paraphyletic Paraphyly is a taxonomic term describing a grouping that consists of the grouping's last common ancestor and some but not all of its descendant lineages. The grouping is said to be paraphyletic ''with respect to'' the excluded subgroups. In co ...

group known as "

Excavata Excavata is an obsolete, extensive and diverse paraphyletic group of unicellular Eukaryota. The group was first suggested by Simpson and Patterson in 1999 and the name latinized and assigned a rank by Thomas Cavalier-Smith in 2002. It contains ...

Evolution

It is clear that the malawimonads are a

monophyletic In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent co ...

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

at the base of

Eukaryota The eukaryotes ( ) constitute the Domain (biology), domain of Eukaryota or Eukarya, organisms whose Cell (biology), cells have a membrane-bound cell nucleus, nucleus. All animals, plants, Fungus, fungi, seaweeds, and many unicellular organisms ...

, but there is no consensus on the specific relationships between other basal groups, such as

Discoba Excavata is an obsolete, extensive and diverse Paraphyly, paraphyletic group of unicellular Eukaryote, Eukaryota. The group was first suggested by Simpson and Patterson in 1999 and the name latinized and assigned a rank by Thomas Cavalier-Smit ...

, Metamonada,

Ancyromonadida Ancyromonadida or Planomonadida is a small group of biflagellated eukaryotes found in the soil and in aquatic habitats, where they feed on bacteria.Cavalier-Smith, T. (2013)Early evolution of eukaryote feeding modes, cell structural diversity, a ...

and

Podiata Podiates (Cavalier-Smith, 2012, excl. Ancyromonadida) are a proposed clade containing the Amorphea (incl. Opisthokonta, Amoebozoa, apusomonads and breviates) and the organisms now assigned to the clade CRuMs. Ancyromonadida does not appear ...

. The

sister group In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and ...

to Malawimonadida varies greatly between analyses. Some

phylogenetic analyses In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as Computational phylogenetics, phylogenetic inference. It infers the relationship among organ ...

find Malawimonadida as the

. Other analyses recover Malawimonadida as the sister group of

or Metamonada. Very few modern analyses recover the three clades,

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

and Metamonada, as a monophyletic

Taxonomy

History

The malawimonads were first described as

order Order, ORDER or Orders may refer to: * A socio-political or established or existing order, e.g. World order, Ancien Regime, Pax Britannica * Categorization, the process in which ideas and objects are recognized, differentiated, and understood ...

Malawimonadida in 2003 by

Thomas Cavalier-Smith Thomas (Tom) Cavalier-Smith, FRS, FRSC, NERC Professorial Fellow (21 October 1942 – 19 March 2021), was a professor of evolutionary biology in the Department of Zoology, at the University of Oxford. His research has led to discov ...

. 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 Loukozoa (From Greek ''loukos'': groove) is a proposed taxon used in some classifications of eukaryotes, consisting of the Metamonada and Malawimonadea. Ancyromonads are closely related to this group, as sister of the entire group, or as sister ...

", a

polyphyletic A polyphyletic group is an assemblage that includes organisms with mixed evolutionary origin but does not include their most recent common ancestor. The term is often applied to groups that share similar features known as Homoplasy, homoplasies ...

group uniting Metamonada,

Jakobea Jakobida is an order (sole order in the class Jakobea) of free-living, heterotrophic, flagellar eukaryotes in the clade Discoba. They are small (less than 15 μm), and can be found in aerobic and anaerobic environments. The order Jakobida, ...

Tsukubea ''Tsukubamonas'' is a unicellular heterotrophic, biflagellated excavate of the Discoba clade (along with jakobids, euglenozoans and percolozoans) with only one species known, ''Tsukubamonas globosa''. It inhabits fresh-water, feeds on bacter ...

and the malawimonads. 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.

Classification

Initially, Malawimonadida was a

monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unisp ...

order, containing only the family Malawimonadidae and the genus ''

Malawimonas ''Malawimonas'' is genus of unicellular, heterotrophic flagellates with uncertain phylogenetic affinities. They have variably being assigned to Excavata and Loukozoa. Recent studies suggest they may be closely related to the Podiata. Discovery ...

''. 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. *Family Imasidae **'' Imasa'' ***'' I. heleensis'' *Family Malawimonadidae **'' Gefionella'' ***'' G. okellyi'' **''

'' ***'' M. jakobiformis'' ***''"M. californiana" or "californiensis"'' (''

nomen nudum In Taxonomy (biology), taxonomy, a ''nomen nudum'' ('naked name'; plural ''nomina nuda'') is a designation which looks exactly like a scientific name of an organism, and may have originally been intended to be one, but it has not been published ...

'')

References

External links

{{Taxonbar, from1=Q21224386, from2=Q21224392 Excavata