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Diaphoretickes () is a major evolutionary lineage, or , of organisms spanning over 600,000 species. They comprise an enormous diversity of life forms, from single-celled to multicellular and numerous types of . The clade was discovered through phylogenetic analyses in the 21st century that revealed a close relationship between the supergroups (or in a broad sense), , , and (, and ).

Before molecular analyses recovered this clade, evolutionary biologist Thomas Cavalier-Smith had already hypothesized an evolutionary proximity between plants and the remaining groups (collectively known as '' in his classification system). He coined the term photokaryotes for these organisms, as they include almost all of the photosynthetic eukaryotes. He later called them corticates due to the presence of in many of their members.

Although Diaphoretickes contains organisms of very different morphologies, they have a few common traits. Ancestrally they are similar to , with two and a ventral feeding groove. In addition, the presence of cortical alveoli and flagellar hairs are interpreted as ancestral traits unique to the group. Some traits appeared convergently in many groups, such as the acquisition of through primary and secondary and the presence of and a -type cell. In particular, chloroplasts with and heliozoan cells are exclusive to Diaphoretickes.

Within Diaphoretickes, Cryptista and the heliozoan Microheliella maris form the clade , which is the closest relative to Archaeplastida, together forming the . Haptista and SAR are closer to each other and to a clade of flagellates known as . In addition, three small groups of protists, , and Meteora sporadica, form a clade that may belong to Diaphoretickes.


Etymology
The name Diaphoretickes derives ( diaforetikés) meaning diverse, dissimilar, referring to the wide morphological and cellular diversity among members of this clade.


History
, organisms whose cells contain a , have been traditionally grouped into four kingdoms: , , and . In the late 20th century, molecular phylogenetic analyses revealed that protists are a assortment of many independent evolutionary lineages or , from which animals, fungi and plants evolved. However, the relationships between these clades remained difficult to assess due to technological limitations. Starting in the early 2000s, improvements on phylogenetics allowed the classification of most eukaryotes into a small number of diverse clades called supergroups.

In 2008, a close evolutionary relationship was discovered between some of these clades: (plants and relatives; sometimes known as kingdom Plantae), (, and ), and two smaller groups of algae, and . This collection of organisms contains almost all eukaryotes capable of .

The SAR, haptophytes and cryptomonads were collectively known as or kingdom due to a hypothesized common ancestor that obtained the ability to photosynthesize, as algae included in them usually contain a unique pigment, . The relationship between plants and chromalveolates had been described earlier by evolutionary biologist Thomas Cavalier-Smith (1942–2021), who referred to the clade containing both groups as photokaryotes since most of their members are photosynthetic. He later called them corticates, suggesting that they share a common ancestor due to the presence of (vesicles underneath the ) in some of their members ( and alveolates). However, these names became obsolete, largely due to the discovery that chromalveolates are not : these algae evolved the ability to photosynthesize independently from one another.

In 2012, a publication by the International Society of Protistologists (ISOP) established a taxonomic name for this clade, Diaphoretickes, with the following phylogenetic definition:

In the following years, higher quality phylogenetic analyses recovered more protists that fall into this definition (e.g., , , ), leading to new clades within Diaphoretickes, such as (centrohelids and haptophytes) and (cryptomonads, katablepharids and relatives).

In 2015, Cavalier-Smith and co-authors rejected the name Diaphoretickes proposed by the ISOP, arguing that it was "an entirely unnecessary, and less euphonious third synonym with no intuitive meaning ... which is destabilising and should not be used". Instead, they suggested converting a pre-existing taxonomic name, , for the superkingdom containing Chromista and Archaeplastida (Plantae). This did not reach consensus, and Diaphoretickes remains widely accepted by the scientific community as the name of this major eukaryotic clade.


Description

Diversity
Diaphoretickes includes eukaryotes of very different morphologies, cellular structures, life cycles and habitats. They range from to highly specialized and even large, organisms like . As such, they include most of the Earth's , with land plants alone occupying over 81% of the total planet biomass. Its major groups are: , , and . Also included is a small group of single-celled known as , which contains 7 species.

Archaeplastida includes organisms with derived directly from a primary endosymbiosis event with a . They amount to an estimated 450,000–500,000 species. Although known as by some authors, archaeplastids include many that do not belong to the multicellular land plants or embryophytes (such as , , , ). These protists are primarily the , algae, and , from which embryophytes evolved. Archaeplastids also include two small groups of heterotrophic flagellates closely related to red algae: and . Embryophytes, green algae and red algae all evolved multicellular forms and complex life cycles independently, but embryophytes are distinguished by the retention of the (fertilized ) as an embryo, instead of its dispersal as a single cell.

The SAR supergroup is named after its three constituent clades: , and . The stramenopiles gather more than 100,000 species in total and comprise many heterotrophic unicellular or fungus-like organisms (e.g., , , , ), but the described diversity is concentrated in the , the photosynthetic clade (e.g., , , ). They are distinguished by the presence of straw-like (flagellar hairs) in one of their two flagella, when present. The alveolates are unicellular protists primarily composed of three large, well-studied groups: (more than 8,000 species, mostly free-living heterotrophs),

(2025). 9783319281476, Springer.
(~4,500 species, many photosynthetic)
(2025). 9783319281476, Springer.
and (more than 6,000 parasitic species), all of which are unicellular.
(2025). 9783319281476, Springer.
In particular, dinoflagellates, apicomplexans and various smaller groups (e.g., ) evolved from a photosynthetic ancestor and are collectively known as .
(2025). 9780128134573, Elsevier.
The rhizarians are a diverse group of mostly unicellular organisms of very different lifestyles, such as the free-living (over 1,000 living species) and (over 6,700 living species), the fungus-like , the parasitic , and the photosynthetic chlorarachniophytes.

Haptista is composed of two groups of single-celled organisms with mineralized scales. The first are the photosynthetic (e.g., the calcifying ), of which there are over 500 living species.

(2025). 9783319281476, Springer.
The second are the heterotrophic amoebae, with around 95 species. Cryptista is a group of fully single-celled flagellated organisms, among which are the photosynthetic (more than 100 species)
(2025). 9783319281476, Springer.
and related heterotrophs, namely the and the species Palpitomonas bilix.


Ancestral traits
Despite their large diversity of forms, a few morphological traits are common to corticates. They are or bikonts, meaning their cells typically have two . Their cells have a ventral groove for feeding, as observed in early-branching species (e.g., the alveolate and the stramenopiles and ). These cellular are typical of , a group composed of the most basal eukaryotes (i.e., , and ); they are likely the ancestral traits of all eukaryotes.

In addition, as opposed to excavates, many Diaphoretickes members have (flattened vesicles beneath the cell surface), such as glaucophytes, alveolates, haptophytes, telonemids and some early-branching stramenopiles (e.g., Kaonashia, ). Due to the wide occurrence of these alveoli, various researchers consider them an ancestral characteristic of Diaphoretickes. Another frequent trait is the presence of flagellar hairs, also considered ancestral and unique to Diaphoretickes.


Convergent traits
Multiple lineages within Diaphoretickes have acquired photosynthetic independently from each other, evolving into . They include all eukaryotic algae except for , which belong to the Discoba. Archaeplastids acquired their plastids directly from primary endosymbiosis with a cyanobacterium, while all other algae have plastids originating from a secondary endosymbiosis with either a red alga (as in ochrophytes, myzozoans, cryptomonads and haptophytes) or a green alga (as in chlorarachniophytes). Red algal-derived plastids are exclusive to the Diaphoretickes clade, while green algal-derived ones are also present in euglenophytes. One rhizarian species, , experienced an event of primary endosymbiosis with a different kind of cyanobacterium.

The exact order of the red algal-derived plastid acquisitions is not yet known. Two main hypotheses agree that cryptophytes were the first to obtain them, and the remaining groups obtained theirs by endosymbiosis with a cryptophyte. A third hypothesis proposed in 2024 suggests that there were two independent endosymbioses of a red alga in cryptophytes and ochrophytes, which in turn originated the plastids of haptophytes and myzozoans, respectively.

Diaphoretickes also includes all that have , stiff filaments used for feeding that branch radially from the cell, a trait acquired independently in various groups. These were historically known as Actinopoda, and were divided into the marine (rhizarians) and the mostly freshwater ("sun animalcules").

(2025). 9783319281490, Springer International Publishing. .
The heliozoa are primarily the centrohelids (relatives of haptophytes), (stramenopiles) and (rhizarians). There are also some lone heliozoan species such as Microheliella maris, the of Cryptista. Even heliozoa that have not been genetically sequenced are presumed to belong to Diaphoretickes. Cavalier-Smith argued that the ancestral configuration of the of corticates was a that made it easier for them to evolve axopodia numerous independent times.


Evolution
Evolutionary relationships are still uncertain between the different clades of Diaphoretickes. and , initially hypothesized as relatives of each other (collectively known as the taxon ), were later revealed to be more distantly related. In particular, Cryptista and the species Microheliella maris form a clade known as , which in turn is the closest relative of , together forming the proposed 'CAM' clade. , previously assigned to Hacrobia, is sometimes resolved as the sister clade of the , forming the hypothesized TSAR clade, while other studies resolve it as more closely related to .

Three small groups of protists—, , and the species Meteora sporadica—form a clade that may be either related to or inside of Diaphoretickes, depending on the analysis. Before phylogenomic data from Meteora and provorans became available, there was already a known affinity between hemimastigotes and Diaphoretickes, although the exact position of hemimastigotes remained unclear. Cavalier-Smith proposed that hemimastigotes were the closest relatives of Diaphoretickes (known by him as corticates), and established the name eucorta ( eu-, 'well-developed' and cortex, 'bark') for their suggested clade, since both groups have a cortical pellicle: with in corticates, and with microtubules and a proteinaceous thickening in hemimastigotes instead. According to the phylogenetic definition of Diaphoretickes, any organism that is more closely related to them than to Discoba or Amorphea is considered part of them, which renders 'eucorta' a synonym of Diaphoretickes.

The following cladogram summarizes the relationships within Diaphoretickes, according to of the 2020s. Chromalveolates are marked *; clades containing heliozoa are marked **.

There is uncertainty regarding relationships with the remaining eukaryotic clades.

(2025). 9783319281490, Springer International Publishing. .
Between Diaphoretickes and , the two major clades of eukaryotes, there are many smaller clades—, , , , , and the aforementioned provoran-hemimastigote- Meteora clade—that may branch closer to one or the other, or closer to the root of the eukaryotic tree, depending on the analysis. Only some analyses find a closer relationship between Diaphoretickes and the clade, together known as . According to a 2021 analysis, Diaphoretickes diverged from other eukaryotes during the (2.2 to 1.6 billion years ago), although the first putative fossils originated during the .


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