Basal (phylogenetics)

In phylogenetics, basal is the direction of the base (or root) of a rooted phylogenetic tree or cladogram. The term may be more strictly applied only to nodes adjacent to the root, or more loosely applied to nodes regarded as being close to the root. Note that extant taxa that lie on branches connecting directly to the root are not more closely related to the root than any other extant taxa.^[1]^[2]^[3]

While there must always be two or more equally "basal" clades sprouting from the root of every cladogram, those clades may differ widely in taxonomic rank,^{[n 1]} species diversity, or both.^{[n 2]} If C is a basal clade within D that has the lowest rank of all basal clades within D,^{[n 3]} C may be described as the basal taxon of that rank within D.^{[n 4]} The concept of a 'key innovation' implies some degree of correlation between evolutionary innovation and diversification.^[4]^[5]^[6]^{[n 5]} However, such a correlation does not make a given case predicable, so ancestral characters should not be imputed to the members of a less species-rich basal clade without additional evidence.^[1]^[2]^[7]^[8]^{[n 6]}

In general, clade A is more basal than clade B if B is a subgroup of the sister group of A or of A itself.^{[n 7]} In the context of large groups, the term "basal" is often used loosely to refer to positions closer to the root than the majority, and in such cases, expressions like "very basal" can appear. A 'core clade' refers to the grouping that encompasses all constituent clades except for the basal clade(s) of the lowest rank within a larger clade, exemplified by core eudicots. No extant taxon is closer to the root than any other.

^ ^a ^b Smith, Stacey (2016-09-19). "For the love of trees: The ancestors are not among us". For the love of trees. Retrieved 2022-03-07.
^ ^a ^b Crisp, Michael D.; Cook, Lyn G (2005). "Do early branching lineages signify ancestral traits?". Trends in Ecology & Evolution. 20 (3): 122–128. doi:10.1111/j.0307-6970.2004.00262.x. PMID 16701355. S2CID 82371239.
^ Krell, Frank-T; Cranston, Peter S. (2004). "Which side of the tree is more basal?". Systematic Entomology. 29 (3): 279–281. doi:10.1016/j.tree.2004.11.010. PMID 16701355. S2CID 12285373.
^ Heard, S.B.; Hauser, D.L. (1995). "Key evolutionary innovations and their ecological mechanisms". Historical Biology. 10 (2): 151–173. doi:10.1080/10292389509380518.
^ Engel, M.S.; Grimaldi, D.A. (2004). "New light shed on the oldest insect". Nature. 427 (6975): 627–630. Bibcode:2004Natur.427..627E. doi:10.1038/nature02291. PMID 14961119. S2CID 4431205.
^ Fernández‐Mazuecos, M.; Blanco‐Pastor, J.L.; Juan, A.; Carnicero, P.; Forrest, A.; Alarcón, M.; Vargas, P.; Glover, B.J. (2019). "Macroevolutionary dynamics of nectar spurs, a key evolutionary innovation". New Phytologist. 222 (2): 1123–1138. doi:10.1111/nph.15654. hdl:10045/89954. PMID 30570752. S2CID 58567195.
^ Baum, D. A. (4 November 2013). "Phylogenetics and the History of Life". The Princeton Guide to Evolution. Princeton University Press. p. 57. ISBN 978-1-4008-4806-5. OCLC 861200134.
^ Cite error: The named reference Jenner2006 was invoked but never defined (see the help page).
^ Krause, J.; Unger, T.; Noçon, A.; Malaspinas, A.; Kolokotronis, S.; Stiller, M.; Soibelzon, L.; Spriggs, H.; Dear, P. H.; Briggs, A. W.; Bray, S. C. E.; O'Brien, S. J.; Rabeder, G.; Matheus, P.; Cooper, A.; Slatkin, M.; Pääbo, S.; Hofreiter, M. (2008). "Mitochondrial genomes reveal an explosive radiation of extinct and extant bears near the Miocene-Pliocene boundary". BMC Evolutionary Biology. 8 (220): 220. doi:10.1186/1471-2148-8-220. PMC 2518930. PMID 18662376.
^ McLellan, Bruce; Reiner, David C. (1994). "A Review of Bear Evolution". Bears: Their Biology and Management. 9 (1): 85–96. doi:10.2307/3872687. JSTOR 3872687.

Cite error: There are <ref group=n> tags on this page, but the references will not show without a {{reflist|group=n}} template (see the help page).

[:0-1] Smith, Stacey (2016-09-19). "For the love of trees: The ancestors are not among us". For the love of trees. Retrieved 2022-03-07.

[:1-2] Crisp, Michael D.; Cook, Lyn G (2005). "Do early branching lineages signify ancestral traits?". Trends in Ecology & Evolution. 20 (3): 122–128. doi:10.1111/j.0307-6970.2004.00262.x. PMID 16701355. S2CID 82371239.

[:2-3] Krell, Frank-T; Cranston, Peter S. (2004). "Which side of the tree is more basal?". Systematic Entomology. 29 (3): 279–281. doi:10.1016/j.tree.2004.11.010. PMID 16701355. S2CID 12285373.

[Heard1995-8] Heard, S.B.; Hauser, D.L. (1995). "Key evolutionary innovations and their ecological mechanisms". Historical Biology. 10 (2): 151–173. doi:10.1080/10292389509380518.

[Engel2004-9] Engel, M.S.; Grimaldi, D.A. (2004). "New light shed on the oldest insect". Nature. 427 (6975): 627–630. Bibcode:2004Natur.427..627E. doi:10.1038/nature02291. PMID 14961119. S2CID 4431205.

[Fernández‐Mazuecos2019-10] Fernández‐Mazuecos, M.; Blanco‐Pastor, J.L.; Juan, A.; Carnicero, P.; Forrest, A.; Alarcón, M.; Vargas, P.; Glover, B.J. (2019). "Macroevolutionary dynamics of nectar spurs, a key evolutionary innovation". New Phytologist. 222 (2): 1123–1138. doi:10.1111/nph.15654. hdl:10045/89954. PMID 30570752. S2CID 58567195.

[Baum2013-12] Baum, D. A. (4 November 2013). "Phylogenetics and the History of Life". The Princeton Guide to Evolution. Princeton University Press. p. 57. ISBN 978-1-4008-4806-5. OCLC 861200134.

[Jenner2006-13] Cite error: The named reference Jenner2006 was invoked but never defined (see the help page).

[krause2008-14] Krause, J.; Unger, T.; Noçon, A.; Malaspinas, A.; Kolokotronis, S.; Stiller, M.; Soibelzon, L.; Spriggs, H.; Dear, P. H.; Briggs, A. W.; Bray, S. C. E.; O'Brien, S. J.; Rabeder, G.; Matheus, P.; Cooper, A.; Slatkin, M.; Pääbo, S.; Hofreiter, M. (2008). "Mitochondrial genomes reveal an explosive radiation of extinct and extant bears near the Miocene-Pliocene boundary". BMC Evolutionary Biology. 8 (220): 220. doi:10.1186/1471-2148-8-220. PMC 2518930. PMID 18662376.

[15] McLellan, Bruce; Reiner, David C. (1994). "A Review of Bear Evolution". Bears: Their Biology and Management. 9 (1): 85–96. doi:10.2307/3872687. JSTOR 3872687.

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