Chromalveolata
| Chromalveolata | |
|---|---|
| |
| Clockwise from top-left: ahaptophyte(coccolithophore:Emiliania huxleyi), somediatoms,awater mold,acryptomonad,andMacrocystis,aphaeophyte | |
Scientific classification
| |
| Domain: | Eukaryota |
| (unranked): | Bikonta |
| (unranked): | Chromalveolata Adl et al., 2005 (not amonophyleticgroup)[1][2] |
| Phyla | |
Chromalveolatawas aeukaryotesupergroup present in a major classification of 2005, then regarded as one of the six major groups within the eukaryotes.[3]It was a refinement of thekingdomChromista,first proposed byThomas Cavalier-Smithin 1981. Chromalveolata was proposed to represent the organisms descended from a single secondaryendosymbiosisinvolving ared algaand abikont.[4]Theplastidsin these organisms are those that containchlorophyll c.
However, themonophylyof the Chromalveolata has been rejected. Thus, two papers published in 2008 have phylogenetic trees in which the chromalveolates are split up,[5][6]and recent studies continue to support this view.[7][8]
Groups and classification
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Historically, many chromalveolates were consideredplants,because of their cell walls, photosynthetic ability, and in some cases their morphological resemblance to the land plants (Embryophyta). However, when thefive-kingdom system(proposed in 1969) took prevalence over the animal–plant dichotomy, most of what we now call chromalveolates were put into the kingdomProtista,but thewater moldsandslime netswere put into the kingdomFungi,while thebrown algaestayed in the plant kingdom. These various organisms were later grouped together and given the name Chromalveolata by Cavalier-Smith. He believed them to be amonophyleticgroup, but this is not the case.[9]
In 2005, in a classification reflecting the consensus at the time, the Chromalveolata were regarded as one of the six majorcladesof eukaryotes.[3]Although not given a formal taxonomic status in this classification, elsewhere the group had been treated as a Kingdom.[citation needed]The Chromalveolata were divided into four major subgroups:
- Cryptophyta
- Haptophyta
- Stramenopiles(or Heterokontophyta)
- Alveolata
Other groups that may be included within, or related to, chromalveolates, are:
Though several groups, such as theciliatesand thewater molds,have lost the ability to photosynthesize, most areautotrophic.All photosynthetic chromalveolates usechlorophyllsaandc,and many useaccessory pigments.Chromalveolates share similarglyceraldehyde 3-phosphate dehydrogenaseproteins.[11]
However, as early as 2005, doubts were being expressed as to whether Chromalveolata was monophyletic,[9]and a review in 2006 noted the lack of evidence for several of the supposed six major eukaryote groups, including the Chromalveolata.[12]In 2012, consensus emerged that the group is not monophyletic. The four original subgroups fall into at least two categories: one comprises the Stramenopiles and the Alveolata, to which theRhizariaare now usually added to form theSAR group;the other comprises the Cryptophyta and the Haptophyta.[5][6]A 2010 paper splits the Cryptophyta and Haptophyta; the former are a sister group to the SAR group, the latter cluster with theArchaeplastida(plants in the broad sense). Thekatablepharidsare closely related to the cryptophytes and thetelonemidsandcentrohelidsmay be related to the haptophytes.[7]
A variety of names have been used for different combinations of the groups formerly thought to make up the Chromalveolata.
- HalvariaAnalyses in 2007 and 2008 agreed that the Stramenopiles and the Alveolata were related, forming a reduced chromalveolate clade, calledHalvaria.[5][6][13]
- SAR groupThe Rhizaria, which were originally not considered to be chromalveolates, belong with the Stramenopiles and Alveolata in many analyses, forming theSAR group,i.e. Halvaria plus Rhizaria.[13][14]
- HacrobiaThe other two groups originally included in Chromalveolata, the Haptophyta and the Cryptophyta, were related in some analyses,[5][6]forming a clade which has been calledHacrobia.Alternatively, the Hacrobia appeared to be more closely related to theArchaeplastida(plants in the very broad sense), being a sister group in one analysis,[5]and actually nested inside this group in another.[6](Earlier,Cavalier-Smithhad suggested a clade calledCorticatafor the grouping ofallthe chromalveolates and the Archaeplastida.) More recently, as noted above, Hacrobia has been split, with the Haptophyta being sister to the SAR group and the Cryptophyta instead related to the Archaeplastida.[7]
Morphology
[edit]Chromalveolates, unlike other groups with multicellular representatives, do not have very many common morphological characteristics. Each major subgroup has certain unique features, including the alveoli of the Alveolata, the haptonema of the Haptophyta, the ejectisome of the Cryptophyta, and the two different flagella of the Heterokontophyta. However, none of these features are present in all of the groups.
The only common chromalveolate features are these:
- The shared origin of chloroplasts, as mentioned above
- Presence ofcellulosein most cell walls
Since this is such a diverse group, it is difficult to summarize shared chromalveolate characteristics.
Ecological role
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Many chromalveolates affect our ecosystem in enormous ways.
Some of these organisms can be very harmful.Dinoflagellatesproducered tides,which can devastate fish populations and intoxicate oyster harvests.Apicomplexansare some of the most successful specific parasites to animals (including the genusPlasmodium,themalariaparasites). Water molds cause several plant diseases - it was the water moldPhytophthora infestansthat caused theIrish potato blight that led to the Great Irish Famine.
However, many others are vital members of our ecosystem.Diatomsare one of the major photosynthetic producers, and as such produce much of theoxygenthat we breathe, and also take in much of thecarbon dioxidefrom the atmosphere.Brown algae,most specificallykelps,create underwater "forest" habitats for many marine creatures, and provide a large portion of the diet of coastal communities.
Chromalveolates also provide many products that we use. Thealginin brown algae is used as a food thickener, most famously inice cream.The siliceous shells of diatoms have many uses, such as in reflective paint, in toothpaste, or as a filter, in what is known asdiatomaceous earth.
Chromalveolata viruses
[edit]Like other organisms, chromalveolata have viruses. In the case ofEmiliania huxleyi(a commonalgal bloomchromalveolate), a virus believed to be specific to it causes mass death and the end of the bloom.[15]
See also
[edit]References
[edit]- ^Laura A. Katz;Jessica R Grant (23 December 2014). "Taxon-rich phylogenomic analyses resolve the eukaryotic tree of life and reveal the power of subsampling by sites".Systematic Biology.64(3): 406–415.doi:10.1093/SYSBIO/SYU126.ISSN1063-5157.PMID25540455.WikidataQ28254627.
- ^Cavalier-Smith, Thomas; Chao, Ema E.; Lewis, Rhodri (2015-12-01)."Multiple origins of Heliozoa from flagellate ancestors: New cryptist subphylum Corbihelia, superclass Corbistoma, and monophyly of Haptista, Cryptista, Hacrobia and Chromista".Molecular Phylogenetics and Evolution.93:331–362.Bibcode:2015MolPE..93..331C.doi:10.1016/j.ympev.2015.07.004.PMID26234272.
- ^abAdl, Sina M.; et al. (2005)."The New Higher Level Classification of Eukaryotes with Emphasis on the Taxonomy of Protists".Journal of Eukaryotic Microbiology.52(5): 399–451.doi:10.1111/j.1550-7408.2005.00053.x.PMID16248873.S2CID8060916.
- ^Keeling PJ (2009). "Chromalveolates and the evolution of plastids by secondary endosymbiosis".J. Eukaryot. Microbiol.56(1): 1–8.doi:10.1111/j.1550-7408.2008.00371.x.PMID19335769.S2CID34259721.
- ^abcdeBurki, Fabien; Shalchian-Tabrizi, Kamran & Pawlowski, Jan (2008)."Phylogenomics reveals a new 'megagroup' including most photosynthetic eukaryotes".Biology Letters.4(4): 366–369.doi:10.1098/rsbl.2008.0224.PMC2610160.PMID18522922.
- ^abcdeKim, E.; Graham, L.E. (Jul 2008). Redfield, Rosemary Jeanne (ed.)."EEF2 analysis challenges the monophyly of Archaeplastida and Chromalveolata".PLOS ONE.3(7): e2621.Bibcode:2008PLoSO...3.2621K.doi:10.1371/journal.pone.0002621.PMC2440802.PMID18612431.
- ^abcBurki, F.; Okamoto, N.; Pombert, J.F. & Keeling, P.J. (2012)."The evolutionary history of haptophytes and cryptophytes: phylogenomic evidence for separate origins".Proc. Biol. Sci.279(1736): 2246–2254.doi:10.1098/rspb.2011.2301.PMC3321700.PMID22298847.
- ^Burki, Fabien; Kaplan, Maia; Tikhonenkov, Denis V.; Zlatogursky, Vasily; Minh, Bui Quang; Radaykina, Liudmila V.; Smirnov, Alexey; Mylnikov, Alexander P.; Keeling, Patrick J. (2016-01-27)."Untangling the early diversification of eukaryotes: a phylogenomic study of the evolutionary origins of Centrohelida, Haptophyta and Cryptista".Proc. R. Soc. B.283(1823): 20152802.doi:10.1098/rspb.2015.2802.ISSN0962-8452.PMC4795036.PMID26817772.
- ^abHarper, J. T., Waanders, E. & Keeling, P. J. 2005. On the monophyly of chromalveolates using a six-protein phylogeny of eukaryotes. Int. J. System. Evol. Microbiol., 55, 487-496."Archived copy"(PDF).Archived fromthe original(PDF)on 2008-12-17.Retrieved2010-04-26.
{{cite web}}:CS1 maint: archived copy as title (link) - ^Shalchian-Tabrizi K, Eikrem W,Klaveness D,Vaulot D, Minge M, Le Gall F, Romari K, Throndsen J, Botnen A, Massana R, Thomsen H, Jakobsen K (2006)."Telonemia, a new protist phylum with affinity to chromist lineages".Proc Biol Sci.273(1595): 1833–42.doi:10.1098/rspb.2006.3515.PMC1634789.PMID16790418.
- ^Takishita K, Yamaguchi H, Maruyama T, Inagaki Y (2009). Zhang B (ed.)."A hypothesis for the evolution of nuclear-encoded, plastid-targeted glyceraldehyde-3-phosphate dehydrogenase genes in" chromalveolate "members".PLOS ONE.4(3): e4737.Bibcode:2009PLoSO...4.4737T.doi:10.1371/journal.pone.0004737.PMC2649427.PMID19270733.
- ^Laura Wegener Parfrey;Erika Barbero; Elyse Lasser; Micah Dunthorn; Debashish Bhattacharya;David J Patterson;Laura A Katz(December 2006)."Evaluating support for the current classification of eukaryotic diversity".PLOS Genetics.2(12): e220.doi:10.1371/JOURNAL.PGEN.0020220.ISSN1553-7390.PMC1713255.PMID17194223.WikidataQ21090155.
- ^abFabien Burki; Kamran Shalchian-Tabrizi; Marianne Minge; Åsmund Skjæveland; Sergey I. Nikolaev; Kjetill S. Jakobsen; Jan Pawlowski (2007)."Phylogenomics Reshuffles the Eukaryotic Supergroups".PLOS ONE.2(8): e790.Bibcode:2007PLoSO...2..790B.doi:10.1371/journal.pone.0000790.PMC1949142.PMID17726520.
- ^Hampl V, Hug L, Leigh JW, et al. (March 2009)."Phylogenomic analyses support the monophyly of Excavata and resolve relationships among eukaryotic" supergroups "".Proc. Natl. Acad. Sci. U.S.A.106(10): 3859–64.Bibcode:2009PNAS..106.3859H.doi:10.1073/pnas.0807880106.PMC2656170.PMID19237557.
- ^Madhusoodanan, Jyoti (August 24, 2014)."Viral demise of an algal bloom:Marine viruses may be key players in the death of massive algal blooms that emerge in the ocean, a study shows".TheScientist.
External links
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