Monophyly

{{Short description|Taxonomic concept}} {{Use dmy dates|date=September 2020}} [[File:Clade-grade II.svg|thumb|300x300px|A phylogenetic tree: both blue and red groups are ''monophyletic''. The green group is ''paraphyletic'': it is missing a monophyletic subgroup – the blue group – that shares a common ancestor with itself. In this form, ''monophyletic'' means "no sideways stems leaving the group".]] [[Image:Monophyly, paraphyly, polyphyly.svg|thumb|300px|A cladogram {{fact|date=October 2025}}of the primates, showing a ''monophyletic'' taxon: the ''simians'' (in yellow); a ''paraphyletic'' taxon: the ''prosimians'' (in cyan, including the red patch); and a ''polyphyletic'' group: ''the night-active primates, i.e., the lorises and the tarsiers'' (in red).]] [[File:Phylogenetic-Groups.svg|thumbnail|300px|A cladogram of the vertebrates showing phylogenetic groups. A ''monophyletic'' taxon (in yellow): ''the group of "reptiles and birds"'', contains its most recent common ancestor and all descendants of that ancestor. A ''paraphyletic'' taxon (in cyan): ''the group of reptiles'', contains its most recent common ancestor, but does not contain all the descendants (namely Aves) of that ancestor. A ''polyphyletic'' "group" (in red): ''the group of all warm-blooded amniotes'' (Aves and Mammalia), does not contain the most recent common ancestor of all its members; this group is not seen as a taxonomic unit and is not considered a taxon by modern systematists.]]

In biological cladistics for the classification of organisms, '''monophyly''' is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria:

# the grouping contains its own most recent common ancestor (or more precisely an ancestral population), i.e. excludes non-descendants of that common ancestor # the grouping contains all the descendants of that common ancestor, without exception

Monophyly is contrasted with paraphyly and polyphyly as shown in the second diagram. A ''paraphyletic'' grouping meets 1. but not 2., thus consisting of the descendants of a common ancestor, excepting one or more monophyletic subgroups. A ''polyphyletic'' grouping meets neither criterion, and instead serves to characterize convergent relationships of biological features rather than genetic relationships – for example, night-active primates, fruit trees, or aquatic insects. As such, these characteristic features of a polyphyletic grouping are not inherited from a common ancestor, but evolved independently.

Monophyletic groups are typically characterised by shared derived characteristics (synapomorphies), which distinguish organisms in the clade from other organisms. An equivalent term is '''holophyly'''.<ref>{{Cite book |last=Allaby |first=Michael |title=A Dictionary of Ecology (5 ed.) |publisher=Oxford University Press |year=2015 |isbn=978-0-19-179315-8 |location=Oxford}}</ref>

The word "mono-phyly" means "one-tribe" in Greek.

These definitions have taken some time to be accepted. When the cladistics school of thought became mainstream in the 1960s, several alternative definitions were in use. Indeed, taxonomists sometimes used terms without defining them, leading to confusion in the early literature,<ref name="Hennig-1999">{{cite book |last1=Hennig |first1=Willi |translator-first1=D. |translator-last1=Davis |translator-first2=R. |translator-last2=Zangerl |title=Phylogenetic Systematics |year=1999 |orig-date=1966 |publisher=Board of Trustees of the University of Illinois |edition=Illinois Reissue |pages=72–77 |isbn=978-0-252-06814-0}}</ref> a confusion which persists.<ref name="Aubert-2015">{{cite journal |last1=Damien |first1=Aubert |date=2015 |title=A formal analysis of phylogenetic terminology: Towards a reconsideration of the current paradigm in systematics |url=https://hal.science/hal-01240878/file/66PhytoN-PhylogeneticTerminology.pdf |journal=Phytoneuron |issue=2015–66 |pages=1–54}}</ref>

The first diagram shows a phylogenetic tree with two monophyletic groups. The several groups and subgroups are particularly situated as branches of the tree to indicate ordered lineal relationships between all the organisms shown. Further, any group may (or may not) be considered a taxon by modern systematics, depending upon the selection of its members in relation to their common ancestor(s); see second and third diagrams.

== Etymology == The term ''monophyly'', or ''monophyletic'', derives from the two Ancient Greek words {{wikt-lang|grc|μόνος}} ({{grc-transl|μόνος}}), meaning "alone, only, unique", and {{wikt-lang|grc|φῦλον}} ({{grc-transl|φῦλον}}), meaning "genus, species",<ref name="Bailly-1981">{{Cite book |title=Abrégé du dictionnaire grec français |last=Bailly |first=Anatole |date=1981-01-01 |publisher=Hachette |isbn=978-2-01-003528-9 |location=Paris |oclc=461974285 }}</ref><ref name="Bailly">{{Cite web |url=http://www.tabularium.be/bailly/ |title=Greek-french dictionary online |last=Bailly |first=Anatole |website=www.tabularium.be |access-date=7 March 2018 |archive-date=18 March 2022 |archive-url=https://web.archive.org/web/20220318000653/http://www.tabularium.be/bailly/ |url-status=dead }}</ref> and refers to the fact that a monophyletic group includes organisms (e.g., genera, species) consisting of all the descendants of a ''unique'' common ancestor.

Conversely, the term ''polyphyly'', or ''polyphyletic'', builds on the ancient Greek prefix {{wikt-lang|grc|πολύς}} ({{grc-transl|πολύς}}), meaning "many, a lot of",<ref name="Bailly-1981"/><ref name="Bailly"/> and refers to the fact that a polyphyletic group includes organisms arising from ''multiple'' ancestral sources.

By comparison, the term ''paraphyly'', or ''paraphyletic'', uses the ancient Greek prefix {{wikt-lang|grc|παρά}} ({{grc-transl|παρά}}), meaning "beside, near",<ref name="Bailly-1981"/><ref name="Bailly"/> and refers to the situation in which one or several monophyletic subgroups are ''left apart'' from all other descendants of a unique common ancestor. That is, a paraphyletic group is ''nearly'' monophyletic, hence the prefix ''{{grc-transl|παρά}}''. {{cn|date=August 2025}}

== Definitions == On the broadest scale, definitions fall into two groups. * Willi Hennig (1966:148) defined monophyly as groups based on synapomorphy (in contrast to paraphyletic groups, based on symplesiomorphy, and polyphyletic groups, based on convergence). Some authors have sought to define monophyly to include paraphyly as any two or more groups sharing a common ancestor.<ref name="Aubert-2015" /><ref name="Colless-1972">{{Cite journal | last1 = Colless | first1 = Donald H. |date=March 1972 | title = Monophyly | journal = Systematic Zoology | volume = 21 | issue = 1 | pages = 126–128 | doi = 10.2307/2412266 | jstor=2412266 }}</ref><ref name="Envall-2008">{{cite journal | doi = 10.1111/j.1095-8312.2008.00984.x | title = On the difference between mono-, holo-, and paraphyletic groups: a consistent distinction of process and pattern | year = 2008 | author = Envall, Mats | journal = Biological Journal of the Linnean Society | volume = 94 | pages = 217–220 | doi-access = free }}</ref><ref name="Ashlock-1971">{{Cite journal | last = Ashlock | first = Peter D. |date=March 1971 | title = Monophyly and Associated Terms | journal = Systematic Zoology | volume = 20 | issue = 1 | pages = 63–69 | doi = 10.2307/2412223 | jstor=2412223 }}</ref> However, this broader definition encompasses both monophyletic and paraphyletic groups as defined above. Therefore, most scientists today restrict the term "monophyletic" to refer to groups consisting of all the descendants of one (hypothetical) common ancestor.<ref name="Hennig-1999"/> However, when considering taxonomic groups such as genera and species, the most appropriate nature of their common ancestor is rather a population. Assuming that it would be one individual or mating pair is unrealistic for sexually reproducing species, which are by definition interbreeding populations.<ref name="Simpson-1961">{{cite book |last=Simpson |first=George |url=https://archive.org/details/principlesofanim0000simp |title=Principles of Animal Taxonomy |publisher=Columbia University Press |year=1990 |isbn=978-0-231-09650-8 |location=New York |url-access=registration}}</ref> * Monophyly (or holophyly) and associated terms are restricted to discussions of taxa, and are not necessarily accurate when used to describe what Hennig called tokogenetic relationships – now referred to as genealogies. Some argue that using a broader definition, such as a species and all its descendants, does not really work to define a genus.<ref name="Simpson-1961"/> The loose definition also fails to recognize the relations of all organisms.<ref>{{Cite web|url=https://www.mun.ca/biology/scarr/Taxon_types.htm|title=Monophyletic, Polyphyletic, & Paraphyletc Taxa|last=Carr|first=Steven M|website=www.mun.ca|access-date=2018-02-23}}</ref> According to D. M. Stamos, a satisfactory cladistic definition of a species or genus is impossible because many species (and even genera) may form by "budding" from an existing species, leaving the parent species paraphyletic; or the species or genera may be the result of hybrid speciation.<ref>{{cite book|last=Stamos|first=D.N.|title=The species problem: biological species, ontology, and the metaphysics of biology|year=2003|publisher=Lexington Books|location=Lanham, Md. [u.a.]|isbn=978-0-7391-0503-0|pages=261–268|url=https://books.google.com/books?id=jPAjv5FsKMYC&q=defining+species+cladistically%27&pg=PA260}}</ref> The concepts of monophyly, paraphyly, and polyphyly have been used in deducing key genes for barcoding of diverse group of species.<ref>{{cite journal |doi=10.1016/j.gene.2019.143967 |title=Diagnosis of mitogenome for robust phylogeny: A case of Cypriniformes fish group |journal=Gene |volume=713 |article-number=143967 |year=2019 |last1=Parhi J., Tripathy P.S., Priyadarshi, H. |first1=Mandal S.C., Pandey P.K. |pmid=31279710 |s2cid=195828782 }}</ref>

== References == {{Reflist}}

== External links == * {{cite web|first=Darren|last=Abbey|year=1994–2006|title=Graphical explanation of basic phylogenetic terms|url=http://www.ucmp.berkeley.edu/glossary/gloss1/phyly.html|publisher=University of California, Berkeley|access-date=15 January 2010}} * {{cite web|first=Steven M.|last=Carr|year=2002|title=Concepts of monophyly, polyphyly & paraphyly|url=https://www.mun.ca/biology/scarr/Taxon_types.htm|publisher=Memorial University|access-date=15 January 2010}} * {{cite web|first=Jaako|last=Hyvönen|year=2005|title=Monophyly, consensus, compromise|url=http://www.helsinki.fi/~jhyvonen/ec05/05_11.11.pdf|publisher=University of Helsinki|access-date=15 January 2010}} * {{cite web |title=Phylogenetic Trees and Classification |url=https://www.digitalatlasofancientlife.org/learn/systematics/phylogenetics/trees-classification/ |website=Digital Atlas of Ancient Life |publisher=Paleontological Research Institution}}

Category:Phylogenetics