Chromista

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The Chromista are a eukaryotic supergroup, probably polyphyletic,[1][2] which may be treated as a separate kingdom or included among the Protista. They include all algae whose chloroplasts contain chlorophylls a and c, as well as various colorless forms that are closely related to them. These are surrounded by four membranes, and are believed to have been acquired from some red algae.

Groups[edit]

Chromista has been defined in different ways at different times. The name Chromista was first introduced by Cavalier-Smith in 1981;[3] the earlier names Chromophyta, Chromobiota and Chromobionta correspond to roughly the same group.

It has been described as consisting of three different groups:[4]

In 2010, Thomas Cavalier-Smith indicated his desire to move Alveolata, Rhizaria and Heliozoa into Chromista.[5]

Some examples of classification of the Chromista and related groups are shown below.[6][7]

Chadefaud, 1950[edit]

The Chromophycées (Chadefaud, 1950), renamed Chromophycota (Chadefaud, 1960), included the current Ochrophyta (autotrophic Stramenopiles), Haptophyta (included in Chrysophyceae until Christensen, 1962), Cryptophyta, Dinophyta, Euglenophyceae and Choanoflagellida (included in Chrysophyceae until Hibberd, 1975).

Christensen 1962, 1989[edit]

The Chromophyta (Christensen 1962, 1989), defined as algae with chlorophyll c, included the current Ochrophyta (autotrophic Stramenopiles), Haptophyta, Cryptophyta, Dinophyta and Choanoflagellida. The Euglenophyceae were transferred to the Chlorophyta.

Bourrelly, 1968[edit]

The Chromophyta (Bourrelly, 1968) included the current Ochrophyta (autotrophic Stramenopiles), Haptophyta and Choanoflagellida. The Cryptophyceae and the Dinophyceae were part of Pyrrhophyta (= Dinophyta).

Cavalier-Smith, 1981[edit]

The Chromista (Cavalier-Smith, 1981) included the current Stramenopiles, Haptophyta and Cryptophyta.

History and controversy[edit]

Molecular trees have had some difficulty resolving relationships between the different groups. All three may share a common ancestor with the alveolates (see chromalveolates), but there is evidence that suggests that the haptophytes and cryptomonads do not belong together with the heterokonts.[1][8]

See also[edit]

References[edit]

  1. ^ a b Laura Wegener Parfrey, Erika Barbero, Elyse Lasser, Micah Dunthorn, Debashish Bhattacharya, David J Patterson, and Laura A Katz (December 2006). "Evaluating Support for the Current Classification of Eukaryotic Diversity". PLoS Genet. 2 (12): e220. doi:10.1371/journal.pgen.0020220. PMC 1713255. PMID 17194223. 
  2. ^ Cavalier-Smith T, Allsopp MT, Chao EE (November 1994). "Chimeric conundra: are nucleomorphs and chromists monophyletic or polyphyletic?". Proc. Natl. Acad. Sci. U.S.A. 91 (24): 11368–72. doi:10.1073/pnas.91.24.11368. PMC 45232. PMID 7972066. 
  3. ^ T. Cavalier-Smith (1981). "Eukaryote kingdoms: seven or nine?". Biosystems 14 (3–4): 461–481. doi:10.1016/0303-2647(81)90050-2. PMID 7337818. 
  4. ^ Csurös M, Rogozin IB, Koonin EV (May 2008). "Extremely intron-rich genes in the alveolate ancestors inferred with a flexible maximum-likelihood approach". Mol. Biol. Evol. 25 (5): 903–11. doi:10.1093/molbev/msn039. PMID 18296415. 
  5. ^ Cavalier-Smith T (June 2010). "Kingdoms Protozoa and Chromista and the eozoan root of the eukaryotic tree". Biol. Lett. 6 (3): 342–5. doi:10.1098/rsbl.2009.0948. PMC 2880060. PMID 20031978. 
  6. ^ Reviers, B. de. (2006). Biologia e Filogenia das Algas. Editora Artmed, Porto Alegre, pp. 156-157.
  7. ^ W. H. Blackwell (2009). Chromista revisited: A dilemma of overlapping putative kingdoms, and the attempted application of the botanical code of nomenclature. Phytologia 91(2).
  8. ^ Burki F, Shalchian-Tabrizi K, Minge M, et al (2007). "Phylogenomics Reshuffles the Eukaryotic Supergroups". In Butler, Geraldine. PLoS ONE 2 (8): e790. doi:10.1371/journal.pone.0000790. PMC 1949142. PMID 17726520. 

External links[edit]