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18-792: See text The Empidoidea are a large monophyletic superfamily of true flies , the sister taxon to the Muscomorpha ( Cyclorrhapha ). These two groups are sometimes united in the unranked taxon Eremoneura . There are some 10,000 known species within Empidoidea, which are represented on all continents except Antarctica. They are known to have existed since the Jurassic period. Empidoidea has been subject to much debate regarding its phylogeny. Based on morphology alone, three major hypotheses had been proposed until 2007 and seemed to be consensus for some time—however, in 2018, Wahlberg & Johanson published

36-453: A node-based clade definition , for example, could be "All descendants of 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

54-421: 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, 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

72-457: A polyphyletic grouping are not inherited from 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

90-583: 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 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

108-815: The Empididae and Dolichopodidae paraphyletic and thus they are retained as subfamilies here. Atelestidae forming the sister group to the rest of Empidoidea is a unanimous result in all studies that have utilized molecular data. The families are: Based on the most recent phylogenetic studies, the internal classification of Empidoidea is as follows: Atelestinae Nemedininae Bicellariinae Drapetini Symballaphthalmini Tachydromiini Trichininae Ocydromiinae Hybotinae Oedaleinae Dolichopodidae Iteaphilinae Ragadinae Clinocerinae Brachystomatini Ceratomerini Trichopezini Chelipodini Empidini Hemerodromiini Hilarini Monophyletic In biological cladistics for

126-444: 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 a goal to identify and eliminate groups that are found to be polyphyletic. This

144-404: The cladistics school of thought became mainstream in 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

162-689: 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 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

180-413: 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,

198-432: 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 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 ,

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216-486: The group are the Empididae and Dolichopodidae , both of which occur worldwide and contain thousands of species . The smaller families were formerly included in the Empididae, but have since been accorded family status. The monophyly of most of these groups have since been confirmed by subsequent studies. The Brachystomatinae and Microphorinae are sometimes elevated to full family status, too, but this would apparently make

234-627: The most current phylogeny supported by extensive genetic data, changing the relationship between quite a few families and tribes. The majority of these insects are predatory , often with large compound eyes (sometimes covering almost the entire surface of the head), and tend to be associated with moist, temperate habitats. Many have a well-developed anal lobe in the wings, and/or a small but distinct anal cell . Several species within Empidoidea are of particular interest to ethologists and ecologists, due to elaborate mating rituals and life histories involving freshwater. The most familiar families in

252-400: The presence of exactly two stamens has developed convergently in many groups. Species have 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

270-494: The recognition of polyphyletic groups in a classification is discouraged. Monophyletic groups (that is, clades ) are considered by these schools of thought to be 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:

288-586: The term paraphyly , or paraphyletic , uses the ancient Greek prefix παρά ( pará ), meaning "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. That is, a paraphyletic group is nearly monophyletic, hence the prefix pará . On the broadest scale, definitions fall into two groups. The concepts of monophyly, paraphyly , and polyphyly have been used in deducing key genes for barcoding of diverse group of species. Polyphyly For example,

306-493: The tree to indicate ordered lineal relationships between all 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

324-405: The two Ancient Greek words πολύς ( polús ) 'many, a lot of', and φῦλον ( phûlon ) 'genus, species', and refers to the fact that 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

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