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23-674: Cuculimorphae Otidimorphae is a clade of birds that contains the orders Cuculiformes (cuckoos), Musophagiformes (turacos), and Otidiformes (bustards) identified in 2014 by genome analysis. George Sangster and colleagues in 2022 named the clade uniting turacos and bustards as Musophagotides , defining it in the PhyloCode as "the least inclusive crown clade containing Otis tarda and Musophaga violacea , but not Grus grus or Mesitornis variegatus ". Cuculiformes (cuckoos) [REDACTED] Musophagiformes (turacos) [REDACTED] Otidiformes (bustards) [REDACTED] While

46-525: A clade (from Ancient Greek κλάδος (kládos)  'branch'), 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 (plural cladi ) is used rather than the English form. Clades are

69-479: A "ladder", with supposedly more "advanced" organisms at the top. Taxonomists have increasingly worked to make the taxonomic system reflect evolution. When it comes to naming , this principle is not always compatible with the traditional rank-based nomenclature (in which only taxa associated with a rank can be named) because not enough ranks exist to name a long series of nested clades. For these and other reasons, phylogenetic nomenclature has been developed; it

92-623: A clade can be described based on two different reference points, crown age and stem age. The crown age of a clade refers to the age of the most recent common ancestor of all of the species in the clade. The stem age of a clade refers to the time that the ancestral lineage of the clade diverged from its sister clade. A clade's stem age is either the same as or older than its crown age. Ages of clades cannot be directly observed. They are inferred, either from stratigraphy of fossils , or from molecular clock estimates. Viruses , and particularly RNA viruses form clades. These are useful in tracking

115-422: A revised taxonomy based on a concept strongly resembling clades, although the term clade itself would not be coined until 1957 by his grandson, Julian Huxley . German biologist Emil Hans Willi Hennig (1913–1976) is considered to be the founder of cladistics . He proposed a classification system that represented repeated branchings of the family tree, as opposed to the previous systems, which put organisms on

138-429: A suffix added should be e.g. "dracohortian". A clade is by definition monophyletic , meaning that it contains one ancestor which can be an organism, a population, or a species and all its descendants. The ancestor can be known or unknown; any and all members of a clade can be extant or extinct. The science that tries to reconstruct phylogenetic trees and thus discover clades is called phylogenetics or cladistics ,

161-499: Is also used with a similar meaning in other fields besides biology, such as historical linguistics ; see Cladistics § In disciplines other than biology . The term "clade" was coined in 1957 by the biologist Julian Huxley to refer to the result of cladogenesis , the evolutionary splitting of a parent species into two distinct species, a concept Huxley borrowed from Bernhard Rensch . Many commonly named groups – rodents and insects , for example – are clades because, in each case,

184-471: Is in turn included in the mammal, vertebrate and animal clades. The idea of a clade did not exist in pre- Darwinian Linnaean taxonomy , which was based by necessity only on internal or external morphological similarities between organisms. Many of the better known animal groups in Linnaeus's original Systema Naturae (mostly vertebrate groups) do represent clades. The phenomenon of convergent evolution

207-509: Is now called Rensch's rule in 1950. It is an allometric law about the relationship between sexual size dimorphism and which sex is larger. It observes that across species size dimorphism increases with increasing body size when the male is the larger sex, and decreases with increasing average body size when the female is the larger sex. He was awarded the Linnean Society of London 's prestigious Darwin-Wallace Medal in 1958. Since 2004,

230-515: Is responsible for many cases of misleading similarities in the morphology of groups that evolved from different lineages. With the increasing realization in the first half of the 19th century that species had changed and split through the ages, classification increasingly came to be seen as branches on the evolutionary tree of life . The publication of Darwin's theory of evolution in 1859 gave this view increasing weight. In 1876 Thomas Henry Huxley , an early advocate of evolutionary theory, proposed

253-489: Is still controversial. As an example, see the full current classification of Anas platyrhynchos (the mallard duck) with 40 clades from Eukaryota down by following this Wikispecies link and clicking on "Expand". The name of a clade is conventionally a plural, where the singular refers to each member individually. A unique exception is the reptile clade Dracohors , which was made by haplology from Latin "draco" and "cohors", i.e. "the dragon cohort "; its form with

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276-656: The German army from 1917 to 1920 and began to observe natural phenomena while he was held prisoner in France. He returned to Germany and began his studies on feather structure under Valentin Haecker (1864–1927) who had himself studied under August Weismann . Until the 1930s Rensch held anti-Darwinian and Lamarckian views. Rensch also took an interest in the philosophy of science and was fascinated by Theodor Ziehen (1862–1950). Rensch also studied expressionist painting and in later life examined

299-538: The Nazi party, and took a position at a zoological garden in Münster . In 1940 he was recalled for military service, but was discharged for medical reasons in 1942. In 1947 he published a book that would later be translated into English under the title Evolution above the species level . The book discussed how the evolutionary mechanisms that drove speciation could also explain the differences between higher taxa . He introduced

322-435: The areas of animal behavior ( ethology ), learning, and memory. Rensch also wrote on human behaviour and he suggested that the human evolutionary connection with organisms would lead to sympathy. He published an autobiography in 1979 and remained scientifically active until his death in 1990. Rensche sought out universal patterns in biology . He was responsible for naming Allen's Rule and Gloger's Rule , and proposed what

345-654: The biological roots of art. He received his Ph.D. from the University of Halle in 1922. He joined the zoological museum of the University of Berlin as an assistant in 1925. In 1927 he participated in a zoological expedition to the Sunda Islands . He studied the geographical distribution of subspecies of polytypic species and of complexes of closely related species with attention to how local environmental factors, especially climate, influenced their evolution. In 1929 he published

368-408: The book Das Prinzip geographischer Rassenkreise und das Problem der Artbildung that discussed the relationship between geography and speciation. His work in this area would influence Ernst Mayr , who was also an assistant at the museum from 1927 to 1930, and would contribute to the development of the modern evolutionary synthesis . In 1937 he was forced to leave the museum because he refused to join

391-416: The bustards seem to be related to the turacos, other genetic studies have found the cuckoos to be closer to the bustards than the turacos are. Musophagiformes (turacos) [REDACTED] Otidiformes (bustards) [REDACTED] Cuculiformes (cuckoos) [REDACTED] This bird-related article is a stub . You can help Misplaced Pages by expanding it . Clade In biological phylogenetics ,

414-476: The concept of Artenkreis (which Mayr translated as a "superspecies" and defined as "a monophyletic group of closely related and largely or entirely allopatric species”). It was considered a major document in the modern synthesis. That same year he became chairman of the zoology department and director of the zoological institute at the University of Münster. In 1953 he would take part in a zoological expedition to India. Later in his career he would work extensively in

437-451: The fundamental unit of cladistics , a modern approach to taxonomy adopted by most biological fields. The common ancestor may be an individual, a population , or a species ( extinct or extant ). Clades are nested, one in another, as each branch in turn splits into smaller branches. These splits reflect evolutionary history as populations diverged and evolved independently. Clades are termed monophyletic (Greek: "one clan") groups. Over

460-546: The group consists of a common ancestor with all its descendant branches. Rodents, for example, are a branch of mammals that split off after the end of the period when the clade Dinosauria stopped being the dominant terrestrial vertebrates 66 million years ago. The original population and all its descendants are a clade. The rodent clade corresponds to the order Rodentia, and insects to the class Insecta. These clades include smaller clades, such as chipmunk or ant , each of which consists of even smaller clades. The clade "rodent"

483-590: The last few decades, the cladistic approach has revolutionized biological classification and revealed surprising evolutionary relationships among organisms. Increasingly, taxonomists try to avoid naming taxa that are not clades; that is, taxa that are not monophyletic . Some of the relationships between organisms that the molecular biology arm of cladistics has revealed include that fungi are closer relatives to animals than they are to plants, archaea are now considered different from bacteria , and multicellular organisms may have evolved from archaea. The term "clade"

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506-518: The latter term coined by Ernst Mayr (1965), derived from "clade". The results of phylogenetic/cladistic analyses are tree-shaped diagrams called cladograms ; they, and all their branches, are phylogenetic hypotheses. Three methods of defining clades are featured in phylogenetic nomenclature : node-, stem-, and apomorphy-based (see Phylogenetic nomenclature§Phylogenetic definitions of clade names for detailed definitions). The relationship between clades can be described in several ways: The age of

529-590: The spread of viral infections . HIV , for example, has clades called subtypes, which vary in geographical prevalence. HIV subtype (clade) B, for example is predominant in Europe, the Americas and Japan, whereas subtype A is more common in east Africa. Bernhard Rensch Rensch was born in Thale and as a young boy, he took an interest in observing the natural world and discovered a talent for drawing and painting. He served in

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