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Related to Sister clade: Cladistic analysis


(klədĭs`tĭks) or

phylogenetic systematics

(fī'lōjənĕt`ĭk), an approach to the classificationclassification,
in biology, the systematic categorization of organisms into a coherent scheme. The original purpose of biological classification, or systematics, was to organize the vast number of known plants and animals into categories that could be named, remembered, and
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 of living things in which organisms are defined and grouped by the possession of one or more shared characteristics (called characters) that are derived from a common ancestor and that were not present in any ancestral group (as envisioned by Charles DarwinDarwin, Charles Robert,
1809–82, English naturalist, b. Shrewsbury; grandson of Erasmus Darwin and of Josiah Wedgwood. He firmly established the theory of organic evolution known as Darwinism.
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's idea of "descent with modification"). Developed by Willi Hennig, a German entomologist, in the 1950s, it is a method of reconstructing evolutionary relationships that emphasizes the importance of descent and common ancestry rather than chronology.

Cladistics places species in a group, or clade, based on a shared character. Within a clade, species that share other characters unique to them are grouped together, and so on, until a cladogram (a branching diagram that resembles a family tree) is assembled. For example, all vertebrates make up a clade; all tetrapods (vertebrates that have four limbs with wrists, ankles, toes, and fingers) form their own clade within the vertebrate clade. In this example the vertebrate clade would be considered "primitive" and the tetrapod clade "derived" or "advanced." In living creatures genetic characters or behaviors as well as more obvious anatomical features might be considered in assembling a cladogram. In paleontologypaleontology
[Gr.,= study of early beings], science of the life of past geologic periods based on fossil remains. Knowledge of the existence of fossils dates back at least to the ancient Greeks, who appear to have regarded them as the remains of various mythological creatures.
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 the characters are necessarily skeletal.

Cladistics is especially significant in paleontology, as it points out gaps in the fossil evidence. It is also felt to be more objective than fossil study, which of necessity extrapolates from a limited number of finds that may or may not be representative of the whole.

See also fossilfossil,
remains or imprints of plants or animals preserved from prehistoric times by the operation of natural conditions. Fossils are found in sedimentary rock, asphalt deposits, and coal and sometimes in amber and certain other materials.
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; datingdating,
the determination of the age of an object, of a natural phenomenon, or of a series of events. There are two basic types of dating methods, relative and absolute.
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Biology a method of grouping animals that makes use of lines of descent rather than structural similarities
References in periodicals archive ?
Micropoltys may belong in the sister clade to these two (which would be clade 62 in Scharff & Coddington 1997, fig.
In these assays, gene segments of another 31 swine isolates were either SYBR green positive/Cy5 negative (online Technical Appendix Figure 1, yellow) or double negative (online Technical Appendix Figure 1, green), indicating that these virus segments were derived from the sister clade of pandemic (H1N1) 2009 virus or other swine lineages (except NA), respectively.
Recent molecular data suggest that Phyllos-cartes and Pogonotriccus are closely related and form a sister clade to Mionectes and Leptopogon (Ohlson et al.
The estimated age of Croton is approximately 55 million years, and the estimated divergence of the Old World clade from its New World sister clade is 40 mya (Fig.
ricketti, which harbors the Chinese sister clade of our coronaviruses, belongs to the same subgenus (Leuconoe Bole) as M.
All other subgenera represent divergent groups displaying unique characters, but synapomorphies and symplesiomorphies among subgenera permit their grouping into separate sister clades.
2007) compared species richness between clades feeding on living plants and their sister clades with hosts other than living plants.
Passoa (1995), Berenbaum and Passoa (1999), and the current analysis find that Agonopterix and Exaeretia are sister clades, unlike Kaila's (2004) analysis, where Agonopterix, Depressaria, Exaeretia, and Levipalpus are all part of an unresolved polytomy.
The phylogeny of 71 complete genomes (avian isolates) and 3 hemagglutinin (HA) sequences (human isolates) in Figure 2B comprises isolates chosen because they formed the European-Middle Eastern-African (EMA) clades and the Russian and Chinese sister clades in a larger analysis of 759 influenza (H5N1) isolates from the locales and host range of all H5N1 sequences published since 1996.
In both rbcL and matK analyses two large sister clades (1 and 2; Figs.