In phylogenetics, a sister group or sister taxon, also called an adelphotaxon,[1] comprises the closest relative(s) of another given unit in an evolutionary tree.[2]
Taxon A and taxon B are sister groups to each other. Taxa A and B, together with any other extant or extinct descendants of their most recent common ancestor (MRCA),[Note 1] form a monophyletic group, the clade AB. Clade AB and taxon C are also sister groups. Taxa A, B, and C, together with all other descendants of their MRCA form the clade ABC.
The whole clade ABC is itself a subtree of a larger tree which offers yet more sister group relationships, both among the leaves and among larger, more deeply rooted clades. The tree structure shown connects through its root to the rest of the universal tree of life.
In cladistic standards, taxa A, B, and C may represent specimens, species, genera, or any other taxonomic units. If A and B are at the same taxonomic level, terminology such as sister species or sister genera can be used.
The term sister group is used in phylogenetic analysis, however, only groups identified in the analysis are labeled as "sister groups".
An example is birds, whose commonly cited living sister group is the crocodiles, but that is true only when discussing extant organisms;[3][4] when other, extinct groups are considered, the relationship between birds and crocodiles appears distant. Although the bird family tree is rooted in the dinosaurs, there were a number of other, earlier groups, such as the pterosaurs, that branched off of the line leading to the dinosaurs after the last common ancestor of birds and crocodiles.[5]
The term sister group must thus be seen as a relative term, with the caveat that the sister group is only the closest relative among the groups/species/specimens that are included in the analysis.[6]
Notesedit
^A tree diagram inevitably oversimplifies the complicated process of evolution.
Referencesedit
^Ultrastructural evidence for an adelphotaxon (sister group) to the Neodermata (Platyhelminthes)
^Eernisse, Douglas J. "Introduction to Phylogeny: What is a Sister Taxon?". Biology 404 - Evolution. Department of Biological Science, California State University, Fullerton. Retrieved 4 January 2012.
^Padian, Kevin; Lindberg, David R.; Polly, Paul David (May 1994). "Cladistics and the fossil record: The uses of history". Annual Review of Earth and Planetary Sciences. 22 (1): 63–89. Bibcode:1994AREPS..22...63P. doi:10.1146/annurev.ea.22.050194.000431.
^Kemp, T.S. (January 1988). "Haemothermia or Archosauria? The interrelationships of mammals, birds and crocodiles". Zoological Journal of the Linnean Society. 92 (1): 67–104. doi:10.1111/j.1096-3642.1988.tb01527.x.
^Hughes, J.M. (2011-06-13). . Aves Vitae - The lives of birds. Archived from the original on 26 April 2012. Retrieved 4 January 2012.
^Podani, János (2010). "Taxonomy in evolutionary perspective - An essay on the relationships between taxonomy and evolutionary theory". Synbiologia Hungarica. 5: 1–42.
February 16, 2024
sister, group, phylogenetics, sister, group, sister, taxon, also, called, adelphotaxon, comprises, closest, relative, another, given, unit, evolutionary, tree, contents, definition, example, notes, referencesdefinition, editthe, expression, most, easily, illus. In phylogenetics a sister group or sister taxon also called an adelphotaxon 1 comprises the closest relative s of another given unit in an evolutionary tree 2 Contents 1 Definition 2 Example 3 Notes 4 ReferencesDefinition editThe expression is most easily illustrated by a cladogram Sister group relationships Root Subtree Taxon A Taxon B Clade AB Taxon C Clade ABC More tree branches Taxon A and taxon B are sister groups to each other Taxa A and B together with any other extant or extinct descendants of their most recent common ancestor MRCA Note 1 form a monophyletic group the clade AB Clade AB and taxon C are also sister groups Taxa A B and C together with all other descendants of their MRCA form the clade ABC The whole clade ABC is itself a subtree of a larger tree which offers yet more sister group relationships both among the leaves and among larger more deeply rooted clades The tree structure shown connects through its root to the rest of the universal tree of life In cladistic standards taxa A B and C may represent specimens species genera or any other taxonomic units If A and B are at the same taxonomic level terminology such as sister species or sister genera can be used Example edit nbsp A Dinosauria phylogeny including two extant taxa birds Theropoda and crocodiles Suchia The term sister group is used in phylogenetic analysis however only groups identified in the analysis are labeled as sister groups An example is birds whose commonly cited living sister group is the crocodiles but that is true only when discussing extant organisms 3 4 when other extinct groups are considered the relationship between birds and crocodiles appears distant Although the bird family tree is rooted in the dinosaurs there were a number of other earlier groups such as the pterosaurs that branched off of the line leading to the dinosaurs after the last common ancestor of birds and crocodiles 5 The term sister group must thus be seen as a relative term with the caveat that the sister group is only the closest relative among the groups species specimens that are included in the analysis 6 Notes edit A tree diagram inevitably oversimplifies the complicated process of evolution References edit Ultrastructural evidence for an adelphotaxon sister group to the Neodermata Platyhelminthes Eernisse Douglas J Introduction to Phylogeny What is a Sister Taxon Biology 404 Evolution Department of Biological Science California State University Fullerton Retrieved 4 January 2012 Padian Kevin Lindberg David R Polly Paul David May 1994 Cladistics and the fossil record The uses of history Annual Review of Earth and Planetary Sciences 22 1 63 89 Bibcode 1994AREPS 22 63P doi 10 1146 annurev ea 22 050194 000431 Kemp T S January 1988 Haemothermia or Archosauria The interrelationships of mammals birds and crocodiles Zoological Journal of the Linnean Society 92 1 67 104 doi 10 1111 j 1096 3642 1988 tb01527 x Hughes J M 2011 06 13 Ancient bird crocodilian ancestor uncovered Aves Vitae The lives of birds Archived from the original on 26 April 2012 Retrieved 4 January 2012 Podani Janos 2010 Taxonomy in evolutionary perspective An essay on the relationships between taxonomy and evolutionary theory Synbiologia Hungarica 5 1 42 Retrieved from https en wikipedia org w index php title Sister group amp oldid 1158035229, wikipedia, wiki, book, books, library,
