Cladistics. (Greek: klados = branch) is a biological tool used to determine the evolutionary relationships between organisms based on relatively derived characters (apomorphs). A derived character is one that has originated from a primitive character. It is currently the most widely accepted phylogenetic method for studying evolutionary relationships between organisms .
Summary
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- 1 Story
- 2 Features
- 3 Cladistic ordinations
- 4 Cladogram
- 5 Application to disciplines other than biology
- 6 Sources
History
The term “subtype” was introduced in 1958 by Julian Huxley , after being coined by Lucien Cunot in 1940 , “cladistic” by Cain and Harrison in 1960 , and “cladist” by Mayr in 1965 . Hennig referred to his own approach as “phylogenetic systematics”. From the time of its original formulation to the end of the 1980s , cladistics maintained a minority approach to both phylogenetics and taxonomy.
In the 1990s , however, it quickly became the dominant game of evolutionary biology’s phylogenetic methods , as computers made it possible to process vast amounts of data about organisms and their characteristics. Almost at the same time, the development of effective polymerase chain reaction techniques allowed the application of cladistics methods to biochemical and molecular genetic traits of organisms, as well as anatomical ones, greatly expanding the amount of data available for phylogenetics. .
The path for computational phylogenetics was paved by phenetics, a set of methods in general use between 1950 and 1980 and, to some extent, later. Phenetics did not try to reconstruct phylogenetic trees, but rather tried to construct dendrograms of data similarity, its algorithms require less power from computers than phylogenetics.
The original method for cladistic analysis and the school of taxonomy derived from it originated from the work of the German entomologist Wilhelm Hennig , who referred to it as “phylogenetic systematics”, the use of the terms “cladistics” and ” subtype “was popularized by other researchers. The techniques and sometimes the names have been successfully applied in other disciplines: for example, to determine relationships between surviving Canterbury Tales manuscripts, or also among the 53 Sanskrit Charaka Samhita manuscripts .
characteristics
Cladistics is a precise method of analysis, which uses the shared apomorphic characters or synapomorphies of the studied organisms (a synapomorphy is a set of derived characters shared by a group of taxa). Cladistic analysis is the basis of most modern biological classification systems that aim to group organisms according to their evolutionary (phylogenetic) relationships.
It is also defined as a biological classification method in which the elements are grouped according to whether or not they have one or more unique shared characteristics that come from the group’s last common ancestor and are not present in the most distant ancestors. Therefore, members of the same group are believed to share a common story and are considered to be more closely related.
Cladistic ordinations
Cladistic ordinations are based on the principle of maximum parsimony. In other words, the relationship system between the groups is established considering the minimum number of transformations necessary to go from the primitive characters (pleisomorphic) to the derived characters (apomophical). Cladistic analysis
Cladistic analysis can be based on as little information as the researcher wants, although modern systematic research generally relies on many different sources of information, including DNA and RNA sequences , biochemical data, and morphological data.
The final result of a cladistic analysis, generally carried out using a computer program, generates a tree-shaped relationship diagram called a ” cladogram “.
Cladogram
In a cladogram, the tips of the branches represent the taxa . Branches should ideally be binary (bifurcations). The two taxa that remain at the ends of a fork are called siblings or sibling groups.
Each subtree is called a clade, regardless of the number of branches it contains. A clade is considered natural when all the organisms it contains share a single ancestor that is not common with any other organism in the cladogram. Each clade is therefore a series of monophyletic descent or lineage defined by a series of characters that appear in its members, but not in the others from which it differs precisely because they lack them. These characters are clade identifiers or synapomorphies (shared derived characters). For example, the circinate prefoliation is a synapomorphy of ferns. The presence of corollas made up of welded petals and a single whorl of stamens is a synapomorphy of the Asteridas .
Application to disciplines other than biology
The comparisons used for data acquisition on which cladograms can be based are not limited to the field of biology. Any group of people or classes that are hypothesized to have a common ancestor, and that a set of common characteristics may or may not apply, can be compared in pairs. Cladograms can be used to represent hypothetical downward relationships within article groups in many different academic realms. The only requirement is that the items have characteristics that can be identified and measured.
Recent attempts to use cladistic methods outside of biology to address lineage reconstruction in:
- Anthropology and archeology : Cladistic methods have been used to reconstruct the development of cultures or artifacts using groups of cultural features or characteristics of the artifact.
- The historical linguistics : cladistic methods have been used to reconstruct the phylogeny of languages with linguistic characteristics. This is similar to the traditional comparative method of historical linguistics, but is more explicit in its use of parsimony and allows much faster analysis of large data sets.
- Textual criticism or stemmatics: cladistic methods have been used to reconstruct the phylogeny of the manuscripts of the same work with the characteristic errors of copying as apomorphies. This differs from traditional historical-comparative linguistics in that it allows the publisher to genetically assess and link large groups of manuscripts with a large number of variants that would be impossible to handle manually. It also allows parsimony analysis of contaminated transmission traditions that would be impossible to assess manually in a reasonable period of time.
- Astrophysics infers the history of the relationships between galaxies to create bifurcation diagrams hypotheses of galaxy diversification .
