Polyphyly

polyphyleticdiphyleticpolyphyletic groupartificial groupbiphyleticpoly-conservative languages that are not closely relatedheterogeneousmonophyleticnonmonophyletic
A polyphyletic group is a set of organisms, or other evolving elements, that have been grouped together but do not share an immediate common ancestor.wikipedia
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Algae

algaalgalfilamentous algae
Other polyphyletic groups are for example algae, C4 photosynthetic plants, and edentates.
Algae (singular alga ) is an informal term for a large, diverse group of photosynthetic eukaryotic organisms that are not necessarily closely related, and is thus polyphyletic.

Alternaria

Researchers concerned more with ecology than with systematics may take polyphyletic groups as legitimate subject matter; the similarities in activity within the fungus group Alternaria, for example, can lead researchers to regard the group as a valid genus while acknowledging its polyphyly.
The genus is now known to be polyphyletic.

Xenarthra

Edentataedentatexenarthran
Other polyphyletic groups are for example algae, C4 photosynthetic plants, and edentates.
Subsequently, Edentata was found to be a polyphyletic grouping whose New World and Old World taxa are unrelated, and it was split up to reflect their true phylogeny.

Monophyly

monophyleticmonophyletic groupnon-monophyletic
. In recent research, the concepts of monophyly, paraphyly, and polyphyly have been used in deducing key genes for barcoding of diverse group of species. Monophyletic groups (that is, clades) are considered by these schools of thought to be the most important grouping of organisms.
Monophyly is contrasted with paraphyly and polyphyly as shown in the second diagram.

Taxonomy (biology)

taxonomictaxonomytaxonomist
In many schools of taxonomy, the existence of polyphyletic groups in a classification is discouraged.
Groups that have descendant groups removed from them are termed paraphyletic, while groups representing more than one branch from the tree of life are called polyphyletic.

Paraphyly

paraphyleticembedded*
. In recent research, the concepts of monophyly, paraphyly, and polyphyly have been used in deducing key genes for barcoding of diverse group of species.
By comparison, the term polyphyly, or polyphyletic, uses the Ancient Greek prefix, meaning "many, a lot of", and refers to the fact that a polyphyletic group includes organisms arising from multiple ancestral sources.

Hybrid speciation

hybrid specieshybridHomoploid hybrid speciation
However hybrid speciation arguably leads to polyphyletic species.
Hybrid species are by their nature polyphyletic.

Phylogenetic nomenclature

stem-based taxonphylogenetic taxonomyphylogenetic classification
One reason for this view is that some clades are simple to define in purely phylogenetic terms without reference to clades previously introduced: a node-based clade definition, for example, could be "All descendants of the last common ancestor of species X and Y".
Names of polyphyletic groups, characterized by a trait that evolved convergently in two or more subgroups, can similarly be defined as the sum of multiple clades.

Clade

cladesgroupcladistic
Monophyletic groups (that is, clades) are considered by these schools of thought to be the most important grouping of organisms.

Convergent evolution

convergentconvergenceanalogous
The term is often applied to groups that share characteristics that appear to be similar but have not been inherited from common ancestors; these characteristics are known as homoplasies, and the development and phenomenon of homoplasies is known as convergent evolution.

C4 carbon fixation

C4C 4 C4 photosynthesis
Other polyphyletic groups are for example algae, C4 photosynthetic plants, and edentates.

Taxon

taxagrouppolytypic
Many biologists aim to avoid homoplasies in grouping taxa together and therefore it is frequently a goal to eliminate groups that are found to be polyphyletic.

Genus

generageneric namegeneric
Researchers concerned more with ecology than with systematics may take polyphyletic groups as legitimate subject matter; the similarities in activity within the fungus group Alternaria, for example, can lead researchers to regard the group as a valid genus while acknowledging its polyphyly.

DNA barcoding

DNA barcodebarcodingbarcoded
. In recent research, the concepts of monophyly, paraphyly, and polyphyly have been used in deducing key genes for barcoding of diverse group of species.

Ancient Greek

GreekClassical GreekGr.
The term polyphyly, or polyphyletic, derives from the two ancient greek words, meaning "many, a lot of", and, meaning "genus, species", and refers to the fact that a polyphyletic group includes organisms (e.g., genera, species) arising from multiple ancestral sources.

Organism

organismsflora and faunaliving organisms
Monophyletic groups (that is, clades) are considered by these schools of thought to be the most important grouping of organisms.

Phylogenetics

phylogeneticphylogenetic analysisphylogenetically
One reason for this view is that some clades are simple to define in purely phylogenetic terms without reference to clades previously introduced: a node-based clade definition, for example, could be "All descendants of the last common ancestor of species X and Y".

Poaceae

grassturfgrass family
For example, classifying a newly discovered grass in the monophyletic family Poaceae, the true grasses, immediately results in numerous predictions about its structure and its developmental and reproductive characteristics, inherited from the common ancestor of this family.

Stamen

antheranthersstamens
In contrast, Linnaeus' assignment of plants with two stamens to the polyphyletic class Diandria, while practical for identification, turns out to be useless for prediction, since the presence of exactly two stamens has developed convergently in many groups.

Species

specificspecific epithetspecific name
Species have a special status in systematics as being an observable feature of nature itself and as the basic unit of classification.

Polyploidy

tetraploidpolyploidtriploid
Hybrid species are a common phenomenon in nature, particularly in plants where polyploidy allows for rapid speciation.

Pteromalidae

pteromalidMuscidifurax raptorpteromalid wasp
The subfamily-level divisions of the family are highly contentious and unstable, and the family unquestionably is completely artificial, composed of numerous, distantly related groups (polyphyletic).

Magnetotactic bacteria

magnetotactic bacteriumMTB
Magnetotactic bacteria (or MTB) are a monophyletic group of bacteria that orient themselves along the magnetic field lines of Earth's magnetic field.

Pteridospermatophyta

seed fernseed fernspteridosperm
The term Pteridospermatophyta (or "seed ferns" or "Pteridospermatopsida") refers to several distinct polyphyletic groups of extinct seed-bearing plants (spermatophytes).