Autapomorphy

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Phylogenies showing the terminology used to describe different patterns of ancestral and derived character or trait states. Autapomorphy.jpg
Phylogenies showing the terminology used to describe different patterns of ancestral and derived character or trait states.

In phylogenetics, an autapomorphy is a distinctive feature, known as a derived trait, that is unique to a given taxon. That is, it is found only in one taxon, but not found in any others or outgroup taxa, not even those most closely related to the focal taxon (which may be a species, family or in general any clade). [2] It can therefore be considered an apomorphy in relation to a single taxon. [3] The word autapomorphy, introduced in 1950 by German entomologist Willi Hennig, is derived from the Greek words αὐτός, autos "self"; ἀπό, apo "away from"; and μορφή, morphḗ = "shape". [4]

Discussion

Because autapomorphies are only present in a single taxon, they do not convey information about relationship. Therefore, autapomorphies are not useful to infer phylogenetic relationships. However, autapomorphy, like synapomorphy and plesiomorphy is a relative concept depending on the taxon in question. An autapomorphy at a given level may well be a synapomorphy at a less-inclusive level. [5] An example of an autapomorphy can be described in modern snakes. Snakes have lost the two pairs of legs that characterize all of Tetrapoda, and the closest taxa to Ophidia – as well as their common ancestors – all have two pairs of legs. Therefore, the Ophidia taxon presents an autapomorphy with respect to its absence of legs. [3]

The autapomorphic species concept is one of many methods that scientists might use to define and distinguish species from one another. This definition assigns species on the basis of amount of divergence associated with reproductive incompatibility, which is measured essentially by number of autapomorphies. [6] This grouping method is often referred to as the "monophyletic species concept" or the "phylospecies" concept and was popularized by D.E. Rosen in 1979. Within this definition, a species is seen as "the least inclusive monophyletic group definable by at least one autapomorphy". [7] While this model of speciation is useful in that it avoids non-monophyletic groupings, it has its criticisms as well. N.I. Platnick, for example, believes the autapomorphic species concept to be inadequate because it allows for the possibility of reproductive isolation and speciation while revoking the "species" status of the mother population. In other words, if a peripheral population breaks away and becomes reproductively isolated, it would conceivably need to develop at least one autapomorphy to be recognized as a different species. If this can happen without the larger mother population also developing a new autapomorphy, then the mother population cannot remain a species under the autapomorphic species concept: it would no longer have any apomorphies not also shared by the daughter species. [8]

Phylogenetic similarities: These phylogenetic terms are used to describe different patterns of ancestral and derived character or trait states as stated in the above diagram in association with synapomorphies. [1]

Related Research Articles

Cladistics is an approach to biological classification in which organisms are categorized in groups ("clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is typically shared derived characteristics (synapomorphies) that are not present in more distant groups and ancestors. However, from an empirical perspective, common ancestors are inferences based on a cladistic hypothesis of relationships of taxa whose character states can be observed. Theoretically, a last common ancestor and all its descendants constitute a (minimal) clade. Importantly, all descendants stay in their overarching ancestral clade. For example, if the terms worms or fishes were used within a strict cladistic framework, these terms would include humans. Many of these terms are normally used paraphyletically, outside of cladistics, e.g. as a 'grade', which are fruitless to precisely delineate, especially when including extinct species. Radiation results in the generation of new subclades by bifurcation, but in practice sexual hybridization may blur very closely related groupings.

<span class="mw-page-title-main">Clade</span> Group of a common ancestor and all descendants

In biological phylogenetics, a clade, also known as a monophyletic group or natural group, is a grouping of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. In the taxonomical literature, sometimes the Latin form cladus is used rather than the English form. Clades are the fundamental unit of cladistics, a modern approach to taxonomy adopted by most biological fields.

<span class="mw-page-title-main">Monophyly</span> Property of a group of including all taxa descendant from a common ancestral species

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

  1. the grouping contains its own most recent common ancestor, i.e. excludes non-descendants of that common ancestor
  2. the grouping contains all the descendants of that common ancestor, without exception

In biology, phylogenetics is the study of the evolutionary history of life using genetics, which known as phylogenetic inference. It establishes the relationship between organisms with the empirical data and observed heritable traits of DNA sequences, protein amino acid sequences, and morphology. The results are a phylogenetic tree—a diagram setting the hypothetical relationships between organisms and their evolutionary history.

In biology, phenetics, also known as taximetrics, is an attempt to classify organisms based on overall similarity, usually with respect to morphology or other observable traits, regardless of their phylogeny or evolutionary relation. It is related closely to numerical taxonomy which is concerned with the use of numerical methods for taxonomic classification. Many people contributed to the development of phenetics, but the most influential were Peter Sneath and Robert R. Sokal. Their books are still primary references for this sub-discipline, although now out of print.

<span class="mw-page-title-main">Paraphyly</span> Type of taxonomic 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 includes a common ancestor and all of its descendants.

<span class="mw-page-title-main">Cladogram</span> Diagram used to show relations among groups of organisms with common origins

A cladogram is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to descendants, nor does it show how much they have changed, so many differing evolutionary trees can be consistent with the same cladogram. A cladogram uses lines that branch off in different directions ending at a clade, a group of organisms with a last common ancestor. There are many shapes of cladograms but they all have lines that branch off from other lines. The lines can be traced back to where they branch off. These branching off points represent a hypothetical ancestor which can be inferred to exhibit the traits shared among the terminal taxa above it. This hypothetical ancestor might then provide clues about the order of evolution of various features, adaptation, and other evolutionary narratives about ancestors. Although traditionally such cladograms were generated largely on the basis of morphological characters, DNA and RNA sequencing data and computational phylogenetics are now very commonly used in the generation of cladograms, either on their own or in combination with morphology.

<span class="mw-page-title-main">Homology (biology)</span> Shared ancestry between a pair of structures or genes in different taxa

In biology, homology is similarity due to shared ancestry between a pair of structures or genes in different taxa. A common example of homologous structures is the forelimbs of vertebrates, where the wings of bats and birds, the arms of primates, the front flippers of whales, and the forelegs of four-legged vertebrates like dogs and crocodiles are all derived from the same ancestral tetrapod structure. Evolutionary biology explains homologous structures adapted to different purposes as the result of descent with modification from a common ancestor. The term was first applied to biology in a non-evolutionary context by the anatomist Richard Owen in 1843. Homology was later explained by Charles Darwin's theory of evolution in 1859, but had been observed before this, from Aristotle onwards, and it was explicitly analysed by Pierre Belon in 1555.

<span class="mw-page-title-main">Polyphyly</span> Property of a group not united by common ancestry

A polyphyletic group is an assemblage that includes organisms with mixed evolutionary origin but does not include their most recent common ancestor. The term is often applied to groups that share similar features known as homoplasies, which are explained as a result of convergent evolution. The arrangement of the members of a polyphyletic group is called a polyphyly. It is contrasted with monophyly and paraphyly.

Evolutionary taxonomy, evolutionary systematics or Darwinian classification is a branch of biological classification that seeks to classify organisms using a combination of phylogenetic relationship, progenitor-descendant relationship, and degree of evolutionary change. This type of taxonomy may consider whole taxa rather than single species, so that groups of species can be inferred as giving rise to new groups. The concept found its most well-known form in the modern evolutionary synthesis of the early 1940s.

<span class="mw-page-title-main">Outgroup (cladistics)</span>

In cladistics or phylogenetics, an outgroup is a more distantly related group of organisms that serves as a reference group when determining the evolutionary relationships of the ingroup, the set of organisms under study, and is distinct from sociological outgroups. The outgroup is used as a point of comparison for the ingroup and specifically allows for the phylogeny to be rooted. Because the polarity (direction) of character change can be determined only on a rooted phylogeny, the choice of outgroup is essential for understanding the evolution of traits along a phylogeny.

<span class="mw-page-title-main">Apomorphy and synapomorphy</span> Two concepts on heritable traits

In phylogenetics, an apomorphy is a novel character or character state that has evolved from its ancestral form. A synapomorphy is an apomorphy shared by two or more taxa and is therefore hypothesized to have evolved in their most recent common ancestor. In cladistics, synapomorphy implies homology.

In phylogenetics and computational phylogenetics, maximum parsimony is an optimality criterion under which the phylogenetic tree that minimizes the total number of character-state changes. Under the maximum-parsimony criterion, the optimal tree will minimize the amount of homoplasy. In other words, under this criterion, the shortest possible tree that explains the data is considered best. Some of the basic ideas behind maximum parsimony were presented by James S. Farris in 1970 and Walter M. Fitch in 1971.

In phylogenetics, long branch attraction (LBA) is a form of systematic error whereby distantly related lineages are incorrectly inferred to be closely related. LBA arises when the amount of molecular or morphological change accumulated within a lineage is sufficient to cause that lineage to appear similar to another long-branched lineage, solely because they have both undergone a large amount of change, rather than because they are related by descent. Such bias is more common when the overall divergence of some taxa results in long branches within a phylogeny. Long branches are often attracted to the base of a phylogenetic tree, because the lineage included to represent an outgroup is often also long-branched. The frequency of true LBA is unclear and often debated, and some authors view it as untestable and therefore irrelevant to empirical phylogenetic inference. Although often viewed as a failing of parsimony-based methodology, LBA could in principle result from a variety of scenarios and be inferred under multiple analytical paradigms.

In phylogenetics, a primitive character, trait, or feature of a lineage or taxon is one that is inherited from the common ancestor of a clade and has undergone little change since. Conversely, a trait that appears within the clade group is called advanced or derived. A clade is a group of organisms that consists of a common ancestor and all its lineal descendants.

<span class="mw-page-title-main">Plesiomorphy and symplesiomorphy</span> Ancestral character or trait state shared by two or more taxa

In phylogenetics, a plesiomorphy and symplesiomorphy are synonyms for an ancestral character shared by all members of a clade, which does not distinguish the clade from other clades.

Phylogenetic nomenclature is a method of nomenclature for taxa in biology that uses phylogenetic definitions for taxon names as explained below. This contrasts with the traditional method, by which taxon names are defined by a type, which can be a specimen or a taxon of lower rank, and a description in words. Phylogenetic nomenclature is regulated currently by the International Code of Phylogenetic Nomenclature (PhyloCode).

<span class="mw-page-title-main">Outline of evolution</span> Overview of and topical guide to change in the heritable characteristics of organisms

The following outline is provided as an overview of and topical guide to evolution:

<span class="mw-page-title-main">Homoplasy</span> Gain or loss of the same feature independently in separate lineages during evolution

Homoplasy, in biology and phylogenetics, is the term used to describe a feature that has been gained or lost independently in separate lineages over the course of evolution. This is different from homology, which is the term used to characterize the similarity of features that can be parsimoniously explained by common ancestry. Homoplasy can arise from both similar selection pressures acting on adapting species, and the effects of genetic drift.

This glossary of genetics and evolutionary biology is a list of definitions of terms and concepts used in the study of genetics and evolutionary biology, as well as sub-disciplines and related fields, with an emphasis on classical genetics, quantitative genetics, population biology, phylogenetics, speciation, and systematics. It has been designed as a companion to Glossary of cellular and molecular biology, which contains many overlapping and related terms; other related glossaries include Glossary of biology and Glossary of ecology.

References

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  2. ↑ Futuyma DJ (1998). Evolutionary Biology (3rd ed.). Sinauer Associates, Inc. p. 95.
  3. 1 2 3 Appel RD, Feytmans E (2009). "Chapter 3: Introduction of Phylogenetics and its Molecular Aspects". Bioinformatics: a Swiss Perspective (1st ed.). World Scientific Publishing Company.
  4. ↑ Calow PP (2009). Encyclopedia of Ecology and Environmental Management. John Wiley & Sons. ISBN   978-1-4443-1324-6. OCLC   1039167559.
  5. ↑ Forey PL (1997). History of the Coelacanth Fishes (1st ed.). Sprinter.
  6. ↑ Howard DJ, Berlocher SH (1998). Endless Forms: Species and Speciation (1st ed.). USA: Oxford University Press. ISBN   978-0-19-510901-6. OCLC   60181901.
  7. ↑ Bull AT (2004). Microbial Diversity and Bioprospecting. ASM Press.
  8. ↑ Platnick NI (2001). "From Cladograms to Classifications: The Road to DePhylocode." (PDF). The Systematics Association.
  9. ↑ Gauger A (April 17, 2012). "Similarity Happens! The Problem of Homoplasy". Evolution Today & Science News.
  10. ↑ Sanderson MJ, Hufford L (21 October 1996). Homoplasy: The Recurrence of Similarity in Evolution. Elsevier. ISBN   978-0-08-053411-4. OCLC   173520205.
  11. ↑ Brandley MC, Warren DL, Leaché AD, McGuire JA (April 2009). "Homoplasy and clade support". Systematic Biology. 58 (2): 184–98. doi: 10.1093/sysbio/syp019 . PMID   20525577.
  12. ↑ Archie JW (September 1989). "Homoplasy Excess Ratios: New Indices for Measuring Levels of Homoplasy in Phylogenetic Systematics and a Critique of the Consistency Index". Systematic Zoology. 38 (3): 253–269. doi:10.2307/2992286. JSTOR   2992286.
  13. ↑ Wake DB, Wake MH, Specht CD (February 2011). "Homoplasy: from detecting pattern to determining process and mechanism of evolution". Science. 331 (6020): 1032–5. Bibcode:2011Sci...331.1032W. doi:10.1126/science.1188545. PMID   21350170. S2CID   26845473.
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  15. ↑ Russell PJ, Hertz PE, McMillan B (2013). Biology: The Dynamic Science. Cengage Learning. ISBN   978-1-285-41534-5.
  16. ↑ Lipscomb D (1998). "Basics of Cladistic Analysis" (PDF). Washington D.C.: George Washington University.
  17. ↑ Choudhuri S (2014-05-09). Bioinformatics for Beginners: Genes, Genomes, Molecular Evolution, Databases and Analytical Tools (1st ed.). Academic Press. p. 51. ISBN   978-0-12-410471-6. OCLC   950546876.
  18. ↑ Williams D, Schmitt M, Wheeler Q (2016-07-21). The Future of Phylogenetic Systematics: The Legacy of Willi Hennig. Cambridge University Press. ISBN   978-1-107-11764-8. OCLC   951563305.
  19. ↑ Avise JC, Robinson TJ (June 2008). "Hemiplasy: a new term in the lexicon of phylogenetics". Systematic Biology. 57 (3): 503–7. doi: 10.1080/10635150802164587 . PMID   18570042.
  20. ↑ Copetti D, Búrquez A, Bustamante E, Charboneau JL, Childs KL, Eguiarte LE, et al. (November 2017). "Extensive gene tree discordance and hemiplasy shaped the genomes of North American columnar cacti". Proceedings of the National Academy of Sciences of the United States of America. 114 (45): 12003–12008. doi: 10.1073/pnas.1706367114 . PMC   5692538 . PMID   29078296.
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