Paraphyly

Source: Wikipedia, the free encyclopedia.

In this phylogenetic tree, the green group is paraphyletic; it is composed of a common ancestor (the lowest green vertical stem) and some of its descendants, but it excludes the blue group (a monophyletic group) which diverged from the green group.

Paraphyly is a

taxonomic term describing a grouping that consists of the grouping's last common ancestor and some but not all of its descendant lineages. The grouping is said to be paraphyletic with respect to the excluded subgroups. In contrast, a monophyletic grouping (a clade
) includes a common ancestor and all of its descendants.

The terms are commonly used in

symplesiomorphies
. If many subgroups are missing from the named group, it is said to be polyparaphyletic.

The term received currency during the debates of the 1960s and 1970s accompanying the rise of cladistics, having been coined by zoologist Willi Hennig to apply to well-known taxa like Reptilia (reptiles), which is paraphyletic with respect to birds. Reptilia contains the last common ancestor of reptiles and all descendants of that ancestor except for birds. Other commonly recognized paraphyletic groups include fish, monkeys, and lizards.[1][page needed]

Etymology

The term paraphyly, or paraphyletic, derives from the two Ancient Greek words παρά (pará), meaning "beside, near", and φῦλον (phûlon), meaning "genus, species",[2][3] and refers to the situation in which one or several monophyletic subgroups of organisms (e.g., genera, species) are left apart from all other descendants of a unique common ancestor.

Conversely, the term monophyly, or monophyletic, builds on the Ancient Greek prefix μόνος (mónos), meaning "alone, only, unique",[2][3] and refers to the fact that a monophyletic group includes organisms consisting of all the descendants of a unique common ancestor.

By comparison, the term polyphyly, or polyphyletic, uses the Ancient Greek prefix πολύς (polús), meaning "many, a lot of",[2][3] and refers to the fact that a polyphyletic group includes organisms arising from multiple ancestral sources.

Phylogenetics

Cladogram of the primates, showing a monophyly (the simians, in yellow), a paraphyly (the prosimians, in blue, including the red patch), and a polyphyly (the night-active primates, the lorises and the tarsiers, in red).

In cladistics

Further information: Cladistics

Groups that include all the descendants of a common ancestor are said to be

monophyletic. A paraphyletic group is a monophyletic group from which one or more subsidiary clades (monophyletic groups) are excluded to form a separate group. Philosopher of science Marc Ereshefsky has argued that paraphyletic taxa are the result of anagenesis in the excluded group or groups.[4] A cladistic approach normally does not grant paraphyletic assemblages the status of "groups", nor does it reify them with explanations, as in cladistics they are not seen as the actual products of evolutionary events.[5]

A group whose identifying features evolved

polyphyletic (Greek πολύς [polys], "many"). More broadly, any taxon that is not paraphyletic or monophyletic can be called polyphyletic. Empirically, the distinction between polyphyletic groups and paraphyletic groups is rather arbitrary, since the character states of common ancestors are inferences, not observations.[citation needed
]

These terms were developed during the debates of the 1960s and 1970s accompanying the rise of cladistics.

Paraphyletic groupings are considered problematic by many taxonomists, as it is not possible to talk precisely about their phylogenetic relationships, their characteristic traits and literal extinction.[6][7] Related terms are stem group, chronospecies, budding cladogenesis, anagenesis, or 'grade' groupings. Paraphyletic groups are often relics from outdated hypotheses of phylogenic relationships from before the rise of cladistics.[8]

Examples

Symphyta
") too are paraphyletic, as the Apocrita are nested inside the Symphytan clades.

The

ICNB with a starting date of 1 January 1980 (in contrast to a 1753 start date under the ICBN/ICN).[10]

Among plants,

dicot ancestor. Excluding monocots from the dicots makes the latter a paraphyletic group.[11]

Among animals, several familiar groups are not, in fact, clades. The order

ICZN Code, the two taxa are separate orders. Molecular studies, however, have shown that the Cetacea descend from artiodactyl ancestors, although the precise phylogeny within the order remains uncertain. Without the Cetaceans the Artiodactyls are paraphyletic.[12]
The class
Diapsida), both of which are "reptiles".[13]

Osteichthyes, bony fish, are paraphyletic when circumscribed to include only Actinopterygii (ray-finned fish) and Sarcopterygii (lungfish, etc.), and to exclude tetrapods; more recently, Osteichthyes is treated as a clade, including the tetrapods.[14][15]

The "

Symphyta) are similarly paraphyletic, forming all of the Hymenoptera except for the Apocrita, a clade deep within the sawfly tree.[14]
Tetraconata.[17][18]

One of the goals of modern taxonomy over the past fifty years has been to eliminate paraphyletic "groups", such as the examples given here, from formal classifications.[19][20]

Paraphyly in species

Main article: Paraspecies

Species have a special status in systematics as being an observable feature of nature itself and as the basic unit of classification.[21] Some articulations of the phylogenetic species concept require species to be monophyletic, but paraphyletic species are common in nature, to the extent that they do not have a single common ancestor. Indeed, for sexually reproducing taxa, no species has a "single common ancestor" organism. Paraphyly is common in speciation, whereby a mother species (a paraspecies) gives rise to a daughter species without itself becoming extinct.[22] Research indicates as many as 20 percent of all animal species and between 20 and 50 percent of plant species are paraphyletic.[23][24] Accounting for these facts, some taxonomists argue that paraphyly is a trait of nature that should be acknowledged at higher taxonomic levels.[25][26]

Cladists advocate a phylogenetic species concept

category error[29]

Uses for paraphyletic groups

When the appearance of significant traits has led a subclade on an evolutionary path very divergent from that of a more inclusive clade, it often makes sense to study the paraphyletic group that remains without considering the larger clade. For example, the

plesiomorphy) from its excluded descendants.[citation needed
]

Also, some systematists recognize paraphyletic groups as being involved in evolutionary transitions, the development of the first tetrapods from their ancestors for example. Any name given to these hypothetical ancestors to distinguish them from tetrapods—"fish", for example—necessarily picks out a paraphyletic group, because the descendant tetrapods are not included.[30] Other systematists consider reification of paraphyletic groups to obscure inferred patterns of evolutionary history.[31]

The term "evolutionary grade" is sometimes used for paraphyletic groups.[32] Moreover, the concepts of monophyly, paraphyly, and polyphyly have been used in deducing key genes for barcoding of diverse group of species.[33]

Independently evolved traits

Current phylogenetic hypotheses of tetrapod relationships imply that

Eulamprus tympanum (or perhaps a synapomorphy, if other Eulamprus species are also viviparous).[citation needed
]

Groupings based on independently-developed traits such as these examples of viviparity represent examples of polyphyly, not paraphyly.[citation needed]

Not paraphyly

Further information: Convergent evolution
  • Amphibious fish are polyphyletic, not paraphyletic. Although they appear similar, several different groups of amphibious fishes such as mudskippers and lungfishes evolved independently in a process of convergent evolution in distant relatives faced with similar ecological circumstances.[34]
  • Flightless birds are polyphyletic because they independently (in parallel) lost the ability to fly.[35]
  • Animals with a dorsal fin are not paraphyletic, even though their last common ancestor may have had such a fin, because the Mesozoic ancestors of porpoises did not have such a fin, whereas pre-Mesozoic fish did have one.
  • Quadrupedal archosaurs are not a paraphyletic group. Bipedal dinosaurs like Eoraptor, ancestral to quadrupedal ones, were descendants of the last common ancestor of quadrupedal dinosaurs and other quadrupedal archosaurs like the crocodilians.

Non-exhaustive list of paraphyletic groups

The following list recapitulates a number of paraphyletic groups proposed in the literature, and provides the corresponding monophyletic taxa.

Paraphyletic taxon Excluded clades Corresponding monophyletic taxon References and notes
Prokaryotes
Eukaryota
 Cellular organisms [36]
Protista
Fungi
 Eukaryota [37]
Invertebrates Vertebrata Animalia [38]
Worm Multiple groups Nephrozoa [39][40]
Radiata Bilateria Eumetazoa [41]
Platyzoa Lophotrochozoa, Mesozoa Spiralia [42]
Fish
Tetrapoda
 Vertebrate [43]
Reptiles
Birds
 Sauropsida [44]
Nonavian Dinosaur Birds Dinosauria
Lizard
Snakes, Amphisbaenia
Squamates
 [45]
Plagiaulacidans
Arginbaataridae
 Multituberculata [46]
Pelycosaurs
Therapsida
 Synapsida [47]
Even-toed ungulates
 Cetacea
Cetartiodactyla
 [12][48]
Archaeoceti
Neoceti
 Cetacea [49]
Prosimians Simiiformes Primates [50]
Crustaceans Hexapoda
Tetraconata
 [17][18]
Wasps
Bees
 Apocrita [16]
Sawfly Apocrita Hymenoptera [14]
Vespoidea
Ants
 Euaculeata [16]
Parasitica Aculeata Apocrita [51]
Nautiloidea
 Ammonoidea, Coleoidea
Cephalopoda
 [52]
Charophyte
 Embryophyte (Land plants) Streptophyta [53]
Dicotyledon Monocotyledon
Angiosperm
 [11]
Moth Butterfly Lepidoptera [54]
Coral Medusozoa, Myxozoa Cnidaria [55][56]
Jellyfish Hydroidolina Medusozoa [57][58][59]
Cycloneuralia Panarthropoda Ecdysozoa [60][61]
Rotifera
 Acanthocephala Syndermata [62][63]
Mecoptera
Siphonaptera
 Mecopteroidea
Anthoathecata Leptothecata, Siphonophorae Hydroidolina
Monkey
Hominoidea
Simiiformes
 [64][65]
Antelope Bovini, Caprinae
Bovidae
 [66]

Linguistics

Main article: Tree model

The concept of paraphyly has also been applied to historical linguistics, where the methods of cladistics have found some utility in comparing languages. For instance, the Formosan languages form a paraphyletic group of the Austronesian languages because they consist of the nine branches of the Austronesian family that are not Malayo-Polynesian and are restricted to the island of Taiwan.[67]

See also

Explanatory notes

  1. ^ The history of flowering plant classification can be found under History of the classification of flowering plants.

References

  1. ^ Romer, A. S. (1970) [1949]. The Vertebrate Body (4th ed.). W.B. Saunders.
  2. ^
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  3. ^ a b c Bailly, Anatole. "Greek-french dictionary online". www.tabularium.be. Retrieved 8 March 2018.
  4. ISBN 978-0-470-05723-0
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  5. ^ Williams, D. M. and Ebach. M. C. 2020. Cladistics: a guide to biological classification. Cambridge University Press.
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  10. ^ Stackebrabdt, E.; Tindell, B.; Ludwig, W.; Goodfellow, M. (1999). "Prokaryotic Diversity and Systematics". In Lengeler, Joseph W.; Drews, Gerhart; Schlegel, Hans Günter (eds.). Biology of the prokaryotes. Stuttgart: Georg Thieme Verlag. p. 679.
  11. ^ a b Simpson 2006, pp. 139–140. "It is now thought that the possession of two cotyledons is an ancestral feature for the taxa of the flowering plants and not an apomorphy for any group within. The 'dicots' ... are paraphyletic ...."
  12. ^
    doi:10.1093/icb/41.3.487
    .
  13. ^ Romer, A. S. & Parsons, T. S. (1985): The Vertebrate Body. (6th ed.) Saunders, Philadelphia.
  14. ^
    doi:10.11646/zootaxa.1668.1.25
    . Symphyta and Apocrita have long been considered as suborders of Hymenoptera but since recognition of the paraphyletic nature of the Symphyta (Köningsmann 1977, Rasnitsyn 1988) and the advent of cladistic methods the subordinal classification should be avoided. Likewise the woodwasps are thought to be non-monophyletic, forming a grade that is ancestral relative to Apocrita and Orussidae. The traditional hymenopteran classification is faulty, by cladistic criteria, in the same way as pre-cladistic vertebrate classifications in which groups sharing plesiomorphic characterswere recognized as natural, e.g., fishes were once grouped together as 'Pisces', which excluded tetrapods.
  15. PMID 23653398. Archived from the original
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  16. ^
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  18. ^
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  19. ^ Schuh, Randall T. "The Linnaean system and its 250-year persistence." The Botanical Review 69, no. 1 (2003): 59.
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    . Retrieved 22 January 2015.
  25. ^ Zander, Richard (2013). Framework for Post-Phylogenetic Systematics. St. Louis: Zetetic Publications, Amazon CreateSpace.
  26. ^ Aubert, D. (2015). "A formal analysis of phylogenetic terminology: Towards a reconsideration of the current paradigm in systematics". Phytoneuron. 66: 1–54.
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  29. S2CID 83900580
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  30. ^ Kazlev, M.A. & White, T. "Amphibians, Systematics, and Cladistics". Palaeos website. Retrieved 16 August 2012.
  31. doi:10.1093/icb/22.2.241
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  32. ISBN 978-0-618-00583-3
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  33. S2CID 195828782
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  35. PMID 18765814
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  36. ISBN 978-0-03-075453-1
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  37. ISSN 1439-6092
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  38. ISBN 978-0-486-15135-9
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  39. OCLC 156823511
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  40. S2CID 29130876
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  41. PMID 12220977
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  42. ^ "Gnathifera - Richard C. Brusca" (PDF).
  43. ^ Tree of life web project – Chordates Archived 24 February 2007 at the Wayback Machine.
  44. ISBN 0-19-860426-2
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  45. PMID 25803280
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  51. ^ Parasitic Hymenoptera (Parasitica). RL Zuparko, Encyclopedia of Entomology, 2004
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  54. ^ Scoble, M.J. (1995). The Lepidoptera: form, function and diversity. Oxford: Oxford University Press. p. 404.
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  63. ^ Shimek, Ronald (January 2006). "Nano-Animals, Part I: Rotifers". Reefkeeping.com. Retrieved 27 July 2008.
  64. ^ AronRa (16 January 2010). Turns out we DID come from monkeys!. Retrieved 12 November 2018.
  65. ^ "Early Primate Evolution: The First Primates". anthro.palomar.edu. Archived from the original on 10 January 2018. Retrieved 12 August 2017.
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  67. ^ Greenhill, Simon J. and Russell D. Gray. (2009.) "Austronesian Language and Phylogenies: Myths and Misconceptions About Bayesian Computational Methods," in Austronesian Historical Linguistics and Culture History: a Festschrift for Robert Blust, edited by Alexander Adelaar and Andrew Pawley. Canberra: Pacific Linguistics, Research School of Pacific and Asian Studies, The Australian National University.

Bibliography

External links

Look up paraphyletic in Wiktionary, the free dictionary.
  • Media related to Paraphyly at Wikimedia Commons
  • Funk, D. J.; Omland, K. E. (2003). "Species-level paraphyly and polyphyly: Frequency, cause and consequences, with insights from animal mitochondrial DNA".
    S2CID 33951905
    .
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