What Should Be the Most Informative Outgroup to the Circled Ingroup

A simple cladogram showing the evolutionary relationships between four species: A, B, C, and D. Here, Species A is the outgroup, and Species B, C, and D form the ingroup.

In cladistics or phylogenetics, an outgroup ^[1] is a more distantly related group of organisms that serves as a reference group when determining the evolutionary relationships of the ingroup, the gear up of organisms under study, and is distinct from sociological outgroups. The outgroup is used every bit a betoken of comparison for the ingroup and specifically allows for the phylogeny to be rooted. Because the polarity (direction) of character alter can be adamant only on a rooted phylogeny, the choice of outgroup is essential for understanding the evolution of traits along a phylogeny.^[2]

History [edit]

Although the concept of outgroups has been in use from the primeval days of cladistics, the term "outgroup" is thought to have been coined in the early 1970s at the American Museum of Natural History.^[iii] Prior to the advent of the term, various other terms were used by evolutionary biologists, including "exgroup", "related grouping", and "outside groups".^[3]

Choice of outgroup [edit]

The chosen outgroup is hypothesized to be less closely related to the ingroup than the ingroup is related to itself. The evolutionary conclusion from these relationships is that the outgroup species has a common ancestor with the ingroup that is older than the common ancestor of the ingroup. Choice of outgroup can modify the topology of a phylogeny.^[iv] Therefore, phylogeneticists typically use more 1 outgroup in cladistic analysis. The use of multiple outgroups is preferable because it provides a more robust phylogeny, buffering against poor outgroup candidates and testing the ingroup's hypothesized monophyly.^{[three] [five] [6]}

To qualify as an outgroup, a taxon must satisfy the following 2 characteristics:

• It must not be a member of the ingroup.
• It must be related to the ingroup, closely enough for meaningful comparisons to the ingroup.

Therefore, an appropriate outgroup must be unambiguously outside the clade of involvement in the phylogenetic study. An outgroup that is nested inside the ingroup volition, when used to root the phylogeny, result in incorrect conclusions almost phylogenetic relationships and trait evolution.^[7] However, the optimal level of relatedness of the outgroup to the ingroup depends on the depth of phylogenetic assay. Choosing a closely related outgroup relative to the ingroup is more than useful when looking at subtle differences, while choosing an disproportionately distant outgroup can outcome in mistaking convergent evolution for a direct evolutionary relationship due to a common antecedent.^{[8] [nine]} For shallow phylogenetics—for example, resolving the evolutionary relationships of a clade inside a genus—an appropriate outgroup would be a member of the sister clade.^[10] Yet, for deeper phylogenetic analysis, less closely related taxa can exist used. For instance, Jarvis et al. (2014) used humans and crocodiles every bit outgroups while resolving the early branches of the avian phylogeny.^[11] In molecular phylogenetics, satisfying the second requirement typically means that Deoxyribonucleic acid or protein sequences from the outgroup can be successfully aligned to sequences from the ingroup. Although in that location are algorithmic approaches to identify the outgroups with maximum global parsimony, they are often express by failing to reflect the continuous, quantitative nature of sure graphic symbol states.^[12] Character states are traits, either bequeathed or derived, that impact the construction of branching patterns in a phylogenetic tree.^[13]

Examples [edit]

Ingroup	Outgroup
Great Apes[14]	Gibbons
Placental mammals[xv]	Marsupials
Chordates[xvi]	Echinoderms
Angiosperms[17]	Gymnosperms

In each example, a phylogeny of organisms in the ingroup may be rooted by scoring the same character states for one or more members of the outgroup.

See too [edit]

• Apomorphy, a derived trait of an organism
• Sister grouping, a group that may be closely related to an ingroup
• Plesiomorphy, an ancestral trait of an organism
• Archaic (phylogenetics), a term for bequeathed traits

References [edit]

1. ^ Grimaldi, David; Engel, Michael S.; Engel, Michael S. (2005-05-xvi). Development of the Insects. ISBN9780521821490.
2. ^ Farris, J. S. (1982). "Outgroups and Parsimony". Systematic Biology. 31 (iii): 328–334. doi:10.1093/sysbio/31.3.328. ISSN 1063-5157.
3. ^ ^{a b c} Nixon, Kevin; Carpenter, James (December 1993). "On Outgroups". Cladistics. 9 (4): 413–426. doi:10.1111/j.1096-0031.1993.tb00234.x. S2CID 221577454.
4. ^ Giribet, G.; Ribera, C. (June 1998). "The position of arthropods in the brute kingdom: a search for a reliable outgroup for internal arthropod phylogeny". Molecular Phylogenetics and Development. 9 (3): 481–488. doi:x.1006/mpev.1998.0494. PMID 9667996.
5. ^ Barriel, 5.; Tassy, P. (June 1998). "Rooting with Multiple Outgroups: Consensus Versus Parsimony". Cladistics. 14 (2): 193–200. doi:10.1111/j.1096-0031.1998.tb00332.x. S2CID 84759858.
6. ^ de la Torre-Barcena, Jose Eduardo; Kolokotronis, Due south.O.; Lee, Ernest; Stevenson, Dennis; Brenner, Eric; Katari, Manpreet; Coruzzi, Gloria; DeSalle, Rob (2009). "The Affect of Outgroup Choice and Missing Data on Major Seed Constitute Phylogenetics Using Genome-Broad EST Data". PLOS Ane. iv (6): e5764. Bibcode:2009PLoSO...4.5764D. doi:ten.1371/journal.pone.0005764. PMC2685480. PMID 19503618.
7. ^ Maddison, Wayne; et al. (1984). "Outgroup Analysis and Parsimony" (PDF). Systematic Zoology. 33 (ane): 83–103. doi:10.2307/2413134. JSTOR 2413134.
8. ^ Wilberg, Eric W. (2015-07-01). "What's in an Outgroup? The Touch of Outgroup Selection on the Phylogenetic Position of Thalattosuchia (Crocodylomorpha) and the Origin of Crocodyliformes". Systematic Biology. 64 (4): 621–637. doi:10.1093/sysbio/syv020. ISSN 1063-5157. PMID 25840332.
9. ^ O'BRIEN, MICHAEL J.; LYMAN, R.LEE; SAAB, YOUSSEF; SAAB, ELIAS; DARWENT, JOHN; GLOVER, DANIEL S. (2002). "Two Issues in Archaeological Phylogenetics: Taxon Construction and Outgroup Selection". Journal of Theoretical Biology. 215 (2): 133–150. doi:10.1006/jtbi.2002.2548. PMID 12051970.
10. ^ David A. Baum; Stacey D. Smith (2013). Tree Thinking: An Introduction to Phylogenetic Biology. Roberts. p. 175. ISBN978-1-936221-16-5.
11. ^ Jarvis, E.; et al. (December 2014). "Whole-genome analyses resolve early branches in the tree of life of modernistic birds". Science. 346 (6215): 1320–1331. Bibcode:2014Sci...346.1320J. doi:10.1126/science.1253451. PMC4405904. PMID 25504713.
12. ^ Stevens, P. F. (1991). "Character States, Morphological Variation, and Phylogenetic Assay: A Review". Systematic Botany. xvi (3): 553–583. doi:10.2307/2419343. JSTOR 2419343.
13. ^ Rineau, Valentin; Grand, Anaïs; Zaragüeta, René; Laurin, Michel (May 1, 2015). "Experimental systematics: sensitivity of cladistic methods to polarization and graphic symbol ordering schemes". Contributions to Zoology. 84 (2): 129–148. doi:10.1163/18759866-08402003.
14. ^ Prado-Martinez, Javier; Marques-Bonet, Tomas (2013). "Swell ape genetic diversity and population history". Nature. 499 (7459): 471–475. Bibcode:2013Natur.499..471P. doi:10.1038/nature12228. PMC3822165. PMID 23823723.
15. ^ Potato, William; Pringle, Thomas; Crider, Tess; Springer, Mark; Miller, Webb (2007). "Using genomic information to unravel the root of the placental mammal phylogeny". Genome Research. 17 (4): 413–421. doi:10.1101/gr.5918807. PMC1832088. PMID 17322288.
16. ^ Cameron, Chris; Garey, James; Swalla, Billie (2000). "Evolution of the chordate body plan: New insights from phylogenetic analyses of deuterostome phyla". PNAS. 97 (nine): 4469–4474. doi:10.1073/pnas.97.9.4469. PMC18258. PMID 10781046.
17. ^ Matthews, Sarah; Donoghue, Michael (1999). "The Root of Angiosperm Phylogeny Inferred from Duplicate Phytochrome Genes". Science. 286 (5441): 947–950. doi:10.1126/science.286.5441.947. PMID 10542147.

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Source: https://en.wikipedia.org/wiki/Outgroup_(cladistics)

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