A comparison of genes within a species or between different species can show similarities between protein functions, or relations between species ( the use of molecular systematics to construct phylogenetic trees ).

# phylogenetic systematics, which uses the above together with the principle of only naming clades as its source of information for taxonomy.

Both the first method for cladistic analysis and the school of taxonomy originated in the work of the German entomologist Willi Hennig, who referred to it as " phylogenetic systematics " ( also the title of his 1966 book ); the use of the terms cladistics and clade was popularized by other researchers.

Hennig referred to his own approach as phylogenetic systematics.

The degree to which taxonomy depends on phylogenies differs between schools of taxonomy: numerical taxonomy ignored phylogeny altogether, trying to represent the similarity between organisms instead ; phylogenetic systematics tries to reproduce phylogeny in its classification without loss of information ; evolutionary taxonomy tries to find a compromise between them in order to represent stages of evolution.

Emil Hans Willi Hennig ( April 20, 1913 – November 5, 1976 ) was a German biologist who is considered the founder of phylogenetic systematics, also known as cladistics.

Evolutionary systematics gives an overview ; phylogenetic systematics gives detail.

* ( 2004 ): Avian molecular systematics on the rebound: a fresh look at modern shorebird phylogenetic relationships.

Molecular systematics is an essentially cladistic approach: it assumes that classification must correspond to phylogenetic descent, and that all valid taxa must be monophyletic.

Cladistics is a technique borrowed from biology, where it was originally named phylogenetic systematics by Willi Hennig.

As a matter of practical convenience the shapes and arrangement of the different sclerites provide most of the morphological features that are used as characters when reconstructing the phylogenetic relationships among different lineages ; they provide the foundation for arthropod systematics, primarily through the ability of the systematist to assess the homologies of the different sclerites, as to how they may be lost, gained, fused, divided, or otherwise modified from one lineage to another.

( 2004 ): Avian molecular systematics on the rebound: a fresh look at modern shorebird phylogenetic relationships.

( 2004 ): Avian molecular systematics on the rebound: a fresh look at modern shorebird phylogenetic relationships.

When several species are compared that way, the similarity values allow the species to be arranged in a phylogenetic tree ; it is therefore one possible approach to carrying out molecular systematics.

* 1950-Willi Hennig publishes Grundzüge einer Theorie der phylogenetischen Systematik in English Basic outline of a theory of phylogenetic systematics.

Neither the biological nor the phylogenetic species concepts, nor phylogenetic systematics can be applied to satisfaction.

Evolutionary taxonomy, evolutionary systematics or Darwinian classification is a branch of biological classification that seeks to classify organisms using a combination of phylogenetic relationship and degree of evolutionary changes.

* Wonderful strife: systematics, stem groups, and the phylogenetic signal of the Cambrian radiation-by Derek Briggs and Richard Fortey

The name was given by Willi Hennig, the formulator of phylogenetic systematics, as a way of classifying living organisms relative to extinct ones.

This is of great importance since studies of Lepidoptera were then, as now, more concerned with species descriptions than with systematics and phylogenetic relationships and the nomenclature was already very confused ( and confusing ).

Rigorously testing these criteria necessitates a synthetic approach, combining areas of research like community ecology, functional morphology, adaptation, quantitative genetics and phylogenetic systematics ( Dayan and Simberloff 2005 ), While satisfying all six criteria in a single study of character displacement is not often feasible, they provide the necessary context for research of character displacement ( Losos 2000, Dayan and Simberloff 2005 ).

The results of phylogenetic / cladistic analyses are tree-shaped diagrams called cladograms ; they, and all their branches, are phylogenetic hypotheses.

These groups appear as the most primitive eukaryotes on phylogenetic trees constructed using rRNA information, which once suggested that they appeared before the origin of mitochondria.

To reflect this phylogenetic proximity, they are termed termed ' stem group tetrapods ' or simply ' stem tetrapods ' - i. e. it lies on a branch more closely related to the lineage that led to tetrapods as recognised by a taxonomist than to their nearest living relatives, the lungfish.

From this data phylogenetic trees can be constructed and evolutionary hypotheses developed using special software like ClustalW regarding the ancestry of modern organisms and the genes they express.

The relationships of these families were uncertain until 2011, when they were resolved in a molecular phylogenetic study based on two nuclear genes and ten chloroplast genes.

and phylogenetic analysis suggests that they are more derived than either of these groups.

By the very nature of a creole language, the phylogenetic classification of a particular creole usually is a matter of dispute ; especially when the pidgin precursor and its parent tongues ( which may have been other creoles or pidgins ) have disappeared before they could be documented.

Discoverers would name these as separate species ( listed below ), and came up with several phylogenetic schemes for how they were related to each other.

Progressive multiple alignment techniques produce a phylogenetic tree by necessity because they incorporate sequences into the growing alignment in order of relatedness.

Although phylogenetic trees produced on the basis of sequenced genes or genomic data in different species can provide evolutionary insight, they have important limitations.

A comparative genomic and phylogenetic analysis of 138 genomes of bacteria, archaea, and eukaryotes found that " the LuxS enzyme required for AI-2 synthesis is widespread in bacteria, while the periplasmic binding protein LuxP is present only in Vibrio strains ," leading to the conclusion that either " other organisms may use components different from the AI-2 signal transduction system of Vibrio strains to sense the signal of AI-2 or they do not have such a quorum sensing system at all.

However, as a phylogenetic unit, they included the mammals as descendants, and in this sense synapsids are still very much a living group of vertebrates.

However, they are an outgroup of the animal phylogenetic tree being that they do not have tissues.

Whilst agglutination is characteristic of certain language families, it would be facile to jump to the conclusion that when several languages in similar geographic area are all agglutinative, they necessarily have to be related in the phylogenetic sense.

( Fain & Houde 2004 ) Arguably, they might be considered an order of their own ( Mesitornithiformes ) as has on occasion been done in the past, but unlike with the Hoatzin, little phylogenetic research has yet been conducted on mesites.

The Iberian Romance languages are conventional Romance languages, many authors use the term in a geographical sense, although they are not necessarily phylogenetic.

More recently, phylogenetic research has questioned whether the bryophytes form a monophyletic group and thus whether they should form a single taxon.

Among bacteria and archaea, selenoproteins are only present in some lineages, while they are completely absent in many other phylogenetic groups.

A recent phylogenetic analysis by May-Collado & Agnarsson ( 2006 ) indicates that two species traditionally assigned to the genus Lagenorhynchus, the Hourglass Dolphin L. cruciger and Peale's Dolphin L. australis are actually phylogenetically nested among the species of Cephalorhynchus, and they suggest that these two species should be transferred to the genus Cephalorhynchus.

Although phylogenetic and evolutionary analysis of parrotfishes is still ongoing, it is now accepted that they are a clade in the tribe Cheilini, and are now commonly referred to as scarine labrids ( subfamily Scarinae, family Labridae ).

Within the Old World Megalaima barbets, they are found to be basal in phylogenetic analyses.