A polyphyletic group is an assemblage that includes organisms with mixed evolutionary origin but does not include their most recent common ancestor. The term is often applied to groups that share similar features known as homoplasies , which are explained as a result of convergent evolution . The arrangement of the members of a polyphyletic group is called a polyphyly / ˈ p ɒ l ɪ ˌ f aɪ l i / . It is contrasted with monophyly and paraphyly .
19-784: Mycetozoa is a polyphyletic grouping of slime molds . It was originally thought to be a monophyletic clade, but recently it was discovered that protostelia are a polyphyletic group within Conosa . It can be divided into dictyostelid , myxogastrid , and protostelid groups. The mycetozoan groups all fit into the unikont supergroup Amoebozoa , whereas most other slime molds fit into various bikont groups ( fonticulids are opisthokonts ). The dictyostelids are used as examples of cell communication and differentiation , and may provide insights into how multicellular organisms develop. Physarum polycephalum are useful for studying cytoplasmic streaming . They have also been used to study
38-468: A common ancestor, but evolved independently. Monophyletic groups are typically characterised by shared derived characteristics ( synapomorphies ), which distinguish organisms in the clade from other organisms. An equivalent term is holophyly . The word "mono-phyly" means "one-tribe" in Greek. These definitions have taken some time to be accepted. When the cladistics school of thought became mainstream in
57-399: A goal to identify and eliminate groups that are found to be polyphyletic. This is often the stimulus for major revisions of the classification schemes. 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
76-444: A polyphyletic group includes organisms (e.g., genera, species) arising from multiple ancestral sources. Conversely, the term monophyly , or monophyletic , employs the ancient Greek adjective μόνος ( mónos ) 'alone, only, unique', and refers to the fact that a monophyletic group includes organisms consisting of all the descendants of a unique common ancestor. By comparison, the term paraphyly , or paraphyletic , uses
95-464: A special status in systematics as being an observable feature of nature itself and as the basic unit of classification. It is usually implicitly assumed that species are monophyletic (or at least paraphyletic ). However, hybrid speciation arguably leads to polyphyletic species. Hybrid species are a common phenomenon in nature, particularly in plants where polyploidy allows for rapid speciation. Some cladist authors do not consider species to possess
114-408: A valid genus while acknowledging its polyphyly. In recent research, the concepts of monophyly, paraphyly, and polyphyly have been used in deducing key genes for barcoding of diverse groups of species. The term polyphyly , or polyphyletic , derives from the two Ancient Greek words πολύς ( polús ) 'many, a lot of', and φῦλον ( phûlon ) 'genus, species', and refers to the fact that
133-553: Is a natural process that can be approximated with partial differential equations . Members of the Mycetozoa group are able to undergo sexual reproduction either by heterothallic or homothallic mating. An analysis of meiosis -related genes in the Dictyostelium discoideum genome revealed that 36 of the 44 genes tested were present in the genome. One gene, Spo11 , was absent in the Mycetozoa, raising questions about
152-412: The 1960s, several alternative definitions were in use. Indeed, taxonomists sometimes used terms without defining them, leading to confusion in the early literature, a confusion which persists. The first diagram shows a phylogenetic tree with two monophyletic groups. The several groups and subgroups are particularly situated as branches of the tree to indicate ordered lineal relationships between all
171-414: The ancient Greek preposition παρά ( pará ) 'beside, near', and refers to the situation in which one or several monophyletic subgroups are left apart from all other descendants of a unique common ancestor. In many schools of taxonomy , the recognition of polyphyletic groups in a classification is discouraged. Monophyletic groups (that is, clades ) are considered by these schools of thought to be
190-465: The assumed universal role of Spo11 as an initiator of meiosis. Polyphyly For example, the biological characteristic of warm-bloodedness evolved separately in the ancestors of mammals and the ancestors of birds; "warm-blooded animals" is therefore a polyphyletic grouping. Other examples of polyphyletic groups are algae , C4 photosynthetic plants , and edentates . Many taxonomists aim to avoid homoplasies in grouping taxa together, with
209-417: The biochemical events that surround mitosis , since all of the nuclei in a medium-sized plasmodium divide in synchrony. It has been observed that they can find their way through mazes by spreading out and choosing the shortest path, an interesting example of information processing without a nervous system . Myxomycete plasmodia have also been used to study the genetics of asexual cell fusion. The giant size of
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#1732798073086228-415: The descendants of a common ancestor, excepting one or more monophyletic subgroups. A polyphyletic grouping meets neither criterion, and instead serves to characterize convergent relationships of biological features rather than genetic relationships – for example, night-active primates, fruit trees, or aquatic insects. As such, these characteristic features of a polyphyletic grouping are not inherited from
247-413: The fact that a monophyletic group includes organisms (e.g., genera, species) consisting of all the descendants of a unique common ancestor. Conversely, the term polyphyly , or polyphyletic , builds on the ancient Greek prefix πολύς ( polús ), meaning "many, a lot of", and refers to the fact that a polyphyletic group includes organisms arising from multiple ancestral sources. By comparison,
266-406: The last common ancestor of species X and Y". On the other hand, polyphyletic groups can be delimited as a conjunction of several clades, for example "the flying vertebrates consist of the bat, bird, and pterosaur clades". From a practical perspective, grouping species monophyletically facilitates prediction far more than does polyphyletic grouping. For example, classifying a newly discovered grass in
285-490: The monophyletic family Poaceae , the true grasses, immediately results in numerous predictions about its structure and its developmental and reproductive characteristics, that are synapomorphies of this family. 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 have
304-403: The only valid groupings of organisms because they are diagnosed ("defined", in common parlance) on the basis of synapomorphies , while paraphyletic or polyphyletic groups are not. From the perspective of ancestry, 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
323-431: The organisms shown. Further, any group may (or may not) be considered a taxon by modern systematics , depending upon the selection of its members in relation to their common ancestor(s); see second and third diagrams. The term monophyly , or monophyletic , derives from the two Ancient Greek words μόνος ( mónos ), meaning "alone, only, unique", and φῦλον ( phûlon ), meaning "genus, species", and refers to
342-522: The plasmodial cells allows for easy evaluation of complete or partial cell fusion. In 2006, researchers at the University of Southampton and the University of Kobe reported that they had built a six-legged robot whose movement was remotely controlled by a Physarum slime mold. The mold directed the robot into a dark corner most similar to its natural habitat. Slime molds are sometimes studied in advanced mathematics courses. Slime mold aggregation
361-456: The property of "-phyly", which they assert applies only to groups of species. Monophyly In biological cladistics for the classification of organisms , monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of taxa which meets these criteria: Monophyly is contrasted with paraphyly and polyphyly as shown in the second diagram. A paraphyletic grouping meets 1. but not 2., thus consisting of
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