64-410: Many, including: Euplotes is a genus of ciliates in the subclass Euplotia. Species are widely distributed in marine and freshwater environments, as well as soil and moss. Most members of the genus are free-living, but two species have been recorded as commensal organisms in the digestive tracts of sea urchins . Euplotes cells are inflexible, dorsoventrally flattened, and roughly ovoid, with
128-499: A BioCode that would regulate all taxon names, but this attempt has so far failed because of firmly entrenched traditions in each community. Consider a particular species, the red fox , Vulpes vulpes : in the context of the Zoological Code , the specific epithet vulpes (small v ) identifies a particular species in the genus Vulpes (capital V ) which comprises all the "true" foxes. Their close relatives are all in
192-420: A "hybrid formula" that specifies the parentage, or may be given a name. For hybrids receiving a hybrid name , the same ranks apply, prefixed with notho (Greek: 'bastard'), with nothogenus as the highest permitted rank. If a different term for the rank was used in an old publication, but the intention is clear, botanical nomenclature specifies certain substitutions: Classifications of five species follow:
256-413: A chain of new organisms); and palintomy (multiple fissions, usually within a cyst ). Fission may occur spontaneously, as part of the vegetative cell cycle . Alternatively, it may proceed as a result of self-fertilization ( autogamy ), or it may follow conjugation , a sexual phenomenon in which ciliates of compatible mating types exchange genetic material. While conjugation is sometimes described as
320-487: A cilium. These are arranged into rows called kineties , which run from the anterior to posterior of the cell. The body and oral kinetids make up the infraciliature , an organization unique to the ciliates and important in their classification, and include various fibrils and microtubules involved in coordinating the cilia. In some forms there are also body polykinetids, for instance, among the spirotrichs where they generally form bristles called cirri . The infraciliature
384-533: A close relationship between the ciliates, Apicomplexa , and dinoflagellates . These superficially dissimilar groups make up the alveolates . Most ciliates are heterotrophs , feeding on smaller organisms, such as bacteria and algae , and detritus swept into the oral groove (mouth) by modified oral cilia. This usually includes a series of membranelles to the left of the mouth and a paroral membrane to its right, both of which arise from polykinetids , groups of many cilia together with associated structures. The food
448-567: A fast evolutionary radiation that occurred long ago, such as the main taxa of placental mammals . In his landmark publications, such as the Systema Naturae , Carl Linnaeus used a ranking scale limited to kingdom, class, order, genus, species, and one rank below species. Today, the nomenclature is regulated by the nomenclature codes . There are seven main taxonomic ranks: kingdom, phylum or division, class, order, family, genus, and species. In addition, domain (proposed by Carl Woese )
512-451: A form of reproduction, it is not directly connected with reproductive processes, and does not directly result in an increase in the number of individual ciliates or their progeny. Ciliate conjugation is a sexual phenomenon that results in genetic recombination and nuclear reorganization within the cell. During conjugation, two ciliates of a compatible mating type form a bridge between their cytoplasms . The micronuclei undergo meiosis ,
576-490: A group of stiff bristles ( caudal cirri), which protrude from the posterior of the cell. The number of caudal cirri varies, even within a species, but it is most common for Euplotes to have 4 or 5. The macronucleus is typically long and narrow, and approximately horseshoe-shaped, C-shaped, or resembling the number 3. Species of Euplotes were first recorded in 1773 by the Danish naturalist O.F. Müller , who placed them in
640-541: A leech cocoon from the Triassic period , about 200 million years ago. According to the 2016 phylogenetic analysis, Mesodiniea is consistently found as the sister group to all other ciliates. Additionally, two big sub-groups are distinguished inside subphylum Intramacronucleata : SAL ( Spirotrichea + Armophorea + Litostomatea ) and CONthreeP or Ventrata ( Colpodea + Oligohymenophorea + Nassophorea + Phyllopharyngea + Plagiopylea + Prostomatea ). The class Protocruziea
704-638: A lower level may be denoted by adding the prefix " infra ", meaning lower , to the rank. For example, infra order (below suborder) or infra family (below subfamily). Botanical ranks categorize organisms based (often) on their relationships ( monophyly is not required by that clade, which does not even mention this word, nor that of " clade "). They start with Kingdom, then move to Division (or Phylum), Class, Order, Family, Genus, and Species. Taxa at each rank generally possess shared characteristics and evolutionary history. Understanding these ranks aids in taxonomy and studying biodiversity. There are definitions of
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#1732783790096768-399: A new rank at will, at any time, if they feel this is necessary. In doing so, there are some restrictions, which will vary with the nomenclature code that applies. The following is an artificial synthesis, solely for purposes of demonstration of absolute rank (but see notes), from most general to most specific: Ranks are assigned based on subjective dissimilarity, and do not fully reflect
832-459: A particular organism, it is usually not necessary to specify names at ranks other than these first two, within a set of taxa covered by a given rank-based code. However, this is not true globally because most rank-based codes are independent from each other, so there are many inter-code homonyms (the same name used for different organisms, often for an animal and for a taxon covered by the botanical code). For this reason, attempts were made at creating
896-417: A single gene . In Tetrahymena , the micronucleus has 10 chromosomes (five per haploid genome), while the macronucleus has over 20,000 chromosomes. In addition, the micronuclear genes are interrupted by numerous "internal eliminated sequences" (IESs). During development of the macronucleus, IESs are deleted and the remaining gene segments, macronuclear destined sequences (MDSs), are spliced together to give
960-576: A taxon in a category above the species level). It should be a natural group (that is, non-artificial, non- polyphyletic ), as judged by a biologist, using all the information available to them. Equally ranked higher taxa in different phyla are not necessarily equivalent in terms of time of origin, phenotypic distinctiveness or number of lower-ranking included taxa (e.g., it is incorrect to assume that families of insects are in some way evolutionarily comparable to families of mollusks). Of all criteria that have been advocated to rank taxa, age of origin has been
1024-451: A very large oral region (peristome) bordered on the left by a long "adoral zone of membranelles " (AZM). Like other spirotrich ciliates, Euplotes move and feed with the help of compound ciliary organelles called "cirri," made up of thick tufts of cilia sparsely distributed on the cell. Strong cirri on the ventral surface of the cell enable Euplotes to walk or crawl on submerged detritus and vegetation. All species of Euplotes have
1088-523: Is accomplished by amitosis , and the segregation of the chromosomes occurs by a process whose mechanism is unknown. After a certain number of generations (200–350, in Paramecium aurelia , and as many as 1,500 in Tetrahymena ) the cell shows signs of aging, and the macronuclei must be regenerated from the micronuclei. Usually, this occurs following conjugation , after which a new macronucleus
1152-564: Is also called a binomial , that is, a two-term name. For example, the zoological name for the human species is Homo sapiens . This is usually italicized in print or underlined when italics are not available. In this case, Homo is the generic name and it is capitalized; sapiens indicates the species and it is not capitalized. While not always used, some species include a subspecific epithet. For instance, modern humans are Homo sapiens sapiens , or H. sapiens sapiens . In zoological nomenclature, higher taxon names are normally not italicized, but
1216-455: Is an unranked taxon within Alveolata . Unlike most other eukaryotes , ciliates have two different sorts of nuclei : a tiny, diploid micronucleus (the "generative nucleus", which carries the germline of the cell), and a large, ampliploid macronucleus (the "vegetative nucleus", which takes care of general cell regulation, expressing the phenotype of the organism). The latter
1280-633: Is found as the sister group to Ventrata / CONthreeP . The class Cariacotrichea was excluded from the analysis, but it was originally established as part of Intramacronucleata . The odontostomatids were identified in 2018 as its own class Odontostomatea , related to Armophorea . Mesodiniea Karyorelictea Heterotrichea Odontostomatea Armophorea Litostomatea Spirotrichea Cariacotrichea Protocruziea Discotrichida Colpodea Nassophorea Phyllopharyngea Oligohymenophorea Prostomatea Plagiopylea Several different classification schemes have been proposed for
1344-439: Is generated from the micronucleus by amplification of the genome and heavy editing. The micronucleus passes its genetic material to offspring, but does not express its genes. The macronucleus provides the small nuclear RNA for vegetative growth. Division of the macronucleus occurs in most ciliate species, apart from those in class Karyorelictea, whose macronuclei are replaced every time the cell divides. Macronuclear division
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#17327837900961408-409: Is generated from the post-conjugal micronucleus. Food vacuoles are formed through phagocytosis and typically follow a particular path through the cell as their contents are digested and broken down by lysosomes so the substances the vacuole contains are then small enough to diffuse through the membrane of the food vacuole into the cell. Anything left in the food vacuole by the time it reaches
1472-451: Is guided by long RNAs derived from the parental macronucleus. More than 95% of micronuclear DNA is eliminated during spirotrich macronuclear development. ln clonal populations of Paramecium , aging occurs over successive generations leading to a gradual loss of vitality, unless the cell line is revitalized by conjugation or autogamy . In Paramecium tetraurelia , the clonally aging line loses vitality and expires after about 200 fissions, if
1536-472: Is known to cause disease in humans. Ciliates reproduce asexually , by various kinds of fission . During fission, the micronucleus undergoes mitosis and the macronucleus elongates and undergoes amitosis (except among the Karyorelictean ciliates, whose macronuclei do not divide). The cell then divides in two, and each new cell obtains a copy of the micronucleus and the macronucleus. Typically,
1600-603: Is moved by the cilia through the mouth pore into the gullet, which forms food vacuoles. Many species are also mixotrophic , combining phagotrophy and phototrophy through kleptoplasty or symbiosis with photosynthetic microbes. The ciliate Halteria has been observed to feed on chloroviruses . Feeding techniques vary considerably, however. Some ciliates are mouthless and feed by absorption ( osmotrophy ), while others are predatory and feed on other protozoa and in particular on other ciliates. Some ciliates parasitize animals , although only one species, Balantidium coli ,
1664-467: Is not a requirement of the zoological and botanical codes. A classification in which all taxa have formal ranks cannot adequately reflect knowledge about phylogeny. Since taxon names are dependent on ranks in rank-based (Linnaean) nomenclature, taxa without ranks cannot be given names. Alternative approaches, such as phylogenetic nomenclature , as implemented under the PhyloCode and supported by
1728-435: Is now widely used as a fundamental rank, although it is not mentioned in any of the nomenclature codes, and is a synonym for dominion ( Latin : dominium ), introduced by Moore in 1974. A taxon is usually assigned a rank when it is given its formal name. The basic ranks are species and genus. When an organism is given a species name it is assigned to a genus, and the genus name is part of the species name. The species name
1792-424: Is one of the main components of the cell cortex . Others are the alveoli , small vesicles under the cell membrane that are packed against it to form a pellicle maintaining the cell's shape, which varies from flexible and contractile to rigid. Numerous mitochondria and extrusomes are also generally present. The presence of alveoli, the structure of the cilia, the form of mitosis and various other details indicate
1856-565: Is ranked as a phylum under any of several kingdoms , including Chromista , Protista or Protozoa . In some older systems of classification, such as the influential taxonomic works of Alfred Kahl , ciliated protozoa are placed within the class " Ciliata " (a term which can also refer to a genus of fish ). In the taxonomic scheme endorsed by the International Society of Protistologists , which eliminates formal rank designations such as "phylum" and "class", "Ciliophora"
1920-479: Is referred to as "isogamontic" conjugation. In some groups, partners are different in size and shape. This is referred to as "anisogamontic" conjugation. In sessile peritrichs , for instance, one sexual partner (the microconjugant) is small and mobile, while the other (macroconjugant) is large and sessile . In Paramecium caudatum , the stages of conjugation are as follows (see diagram at right): Ciliates contain two types of nuclei: somatic " macronucleus " and
1984-402: Is the relative or absolute level of a group of organisms (a taxon ) in a hierarchy that reflects evolutionary relationships. Thus, the most inclusive clades (such as Eukarya and Opisthokonta ) have the highest ranks, whereas the least inclusive ones (such as Homo sapiens or Bufo bufo ) have the lowest ranks. Ranks can be either relative and be denoted by an indented taxonomy in which
Euplotes - Misplaced Pages Continue
2048-789: The Botanical Code , the Prokaryotic Code , the Code for Viruses , the draft BioCode and the PhyloCode all recommend italicizing all taxon names (of all ranks). There are rules applying to the following taxonomic ranks in the International Code of Zoological Nomenclature : superfamily, family, subfamily, tribe, subtribe, genus, subgenus, species, subspecies. The International Code of Zoological Nomenclature divides names into "family-group names", "genus-group names" and "species-group names". The Code explicitly mentions
2112-411: The International Society for Phylogenetic Nomenclature , or using circumscriptional names , avoid this problem. The theoretical difficulty with superimposing taxonomic ranks over evolutionary trees is manifested as the boundary paradox which may be illustrated by Darwinian evolutionary models. There are no rules for how many species should make a genus, a family, or any other higher taxon (that is,
2176-558: The PhyloCode , the code of phylogenetic nomenclature , does not require absolute ranks. Taxa are hierarchical groups of organisms, and their ranks describes their position in this hierarchy. High-ranking taxa (e.g. those considered to be domains or kingdoms, for instance) include more sub-taxa than low-ranking taxa (e.g. those considered genera, species or subspecies). The rank of these taxa reflects inheritance of traits or molecular features from common ancestors. The name of any species and genus are basic ; which means that to identify
2240-427: The fruit fly familiar in genetics laboratories ( Drosophila melanogaster ), humans ( Homo sapiens ), the peas used by Gregor Mendel in his discovery of genetics ( Pisum sativum ), the "fly agaric" mushroom Amanita muscaria , and the bacterium Escherichia coli . The eight major ranks are given in bold; a selection of minor ranks are given as well. Taxa above the genus level are often given names based on
2304-617: The germline " micronucleus ". Only the DNA in the micronucleus is passed on during sexual reproduction (conjugation). On the other hand, only the DNA in the macronucleus is actively expressed and results in the phenotype of the organism. Macronuclear DNA is derived from micronuclear DNA by amazingly extensive DNA rearrangement and amplification. The macronucleus begins as a copy of the micronucleus. The micronuclear chromosomes are fragmented into many smaller pieces and amplified to give many copies. The resulting macronuclear chromosomes often contain only
2368-418: The type genus , with a standard termination. The terminations used in forming these names depend on the kingdom (and sometimes the phylum and class) as set out in the table below. Pronunciations given are the most Anglicized . More Latinate pronunciations are also common, particularly / ɑː / rather than / eɪ / for stressed a . There is an indeterminate number of ranks, as a taxonomist may invent
2432-633: The American Ornithologists' Union published in 1886 states "No one appears to have suspected, in 1842 [when the Strickland code was drafted], that the Linnaean system was not the permanent heritage of science, or that in a few years a theory of evolution was to sap its very foundations, by radically changing men's conceptions of those things to which names were to be furnished." Such ranks are used simply because they are required by
2496-604: The cause of aging in P. tetraurelia . Until recently, the oldest ciliate fossils known were tintinnids from the Ordovician period . In 2007, Li et al. published a description of fossil ciliates from the Doushantuo Formation , about 580 million years ago, in the Ediacaran period . These included two types of tintinnids and a possible ancestral suctorian. A fossil Vorticella has been discovered inside
2560-423: The cell is divided transversally, with the anterior half of the ciliate (the proter ) forming one new organism, and the posterior half (the opisthe ) forming another. However, other types of fission occur in some ciliate groups. These include budding (the emergence of small ciliated offspring, or "swarmers", from the body of a mature parent); strobilation (multiple divisions along the cell body, producing
2624-470: The cell line is not rejuvenated by conjugation or self-fertilization. The basis for clonal aging was clarified by the transplantation experiments of Aufderheide in 1986 who demonstrated that the macronucleus, rather than the cytoplasm, is responsible for clonal aging. Additional experiments by Smith-Sonneborn, Holmes and Holmes, and Gilley and Blackburn demonstrated that, during clonal aging, DNA damage increases dramatically. Thus, DNA damage appears to be
Euplotes - Misplaced Pages Continue
2688-433: The ciliate phylum known to be pathogenic to humans is Balantidium coli , which causes the disease balantidiasis . It is not pathogenic to the domestic pig, the primary reservoir of this pathogen. Taxonomic rank In biology , taxonomic rank (which some authors prefer to call nomenclatural rank because ranking is part of nomenclature rather than taxonomy proper, according to some definitions of these terms)
2752-431: The ciliates. The following scheme is based on a molecular phylogenetic analysis of up to four genes from 152 species representing 110 families: Some old classifications included Opalinidae in the ciliates. The fundamental difference between multiciliate flagellates (e.g., hemimastigids , Stephanopogon , Multicilia , opalines ) and ciliates is the presence of macronuclei in ciliates alone. The only member of
2816-535: The cytoproct ( anal pore ) is discharged by exocytosis . Most ciliates also have one or more prominent contractile vacuoles , which collect water and expel it from the cell to maintain osmotic pressure , or in some function to maintain ionic balance. In some genera, such as Paramecium , these have a distinctive star shape, with each point being a collecting tube. Mostly, body cilia are arranged in mono- and dikinetids , which respectively include one and two kinetosomes (basal bodies), each of which may support
2880-432: The family Canidae , which includes dogs, wolves, jackals, and all foxes; the next higher major taxon, Carnivora (considered an order), includes caniforms (bears, seals, weasels, skunks, raccoons and all those mentioned above), and feliforms (cats, civets, hyenas, mongooses). Carnivorans are one group of the hairy, warm-blooded, nursing members of the class Mammalia , which are classified among animals with notochords in
2944-599: The following ranks for these categories: The rules in the Code apply to the ranks of superfamily to subspecies, and only to some extent to those above the rank of superfamily. Among "genus-group names" and "species-group names" no further ranks are officially allowed, which creates problems when naming taxa in these groups in speciose clades, such as Rana . Zoologists sometimes use additional terms such as species group , species subgroup , species complex and superspecies for convenience as extra, but unofficial, ranks between
3008-464: The following taxonomic categories in the International Code of Nomenclature for Cultivated Plants : cultivar group , cultivar , grex . The rules in the ICN apply primarily to the ranks of family and below, and only to some extent to those above the rank of family. (See also descriptive botanical name .) Taxa at the rank of genus and above have a botanical name in one part (unitary name); those at
3072-410: The genus Trichoda . In 1830,German microscopist C.G. Ehrenberg created the genus Euplotes . By 1975, over 80 species and varieties had been described and assigned to Euplotes . In older classification schemes, Euplotes is usually placed among hypotrichs , either in the order Hypotrichida, the subclass Hypotrichia or the class Hypotrichea. In current classification, Euplotes is placed apart from
3136-480: The gradational nature of variation within nature. These problems were already identified by Willi Hennig , who advocated dropping them in 1969, and this position gathered support from Graham C. D. Griffiths only a few years later. In fact, these ranks were proposed in a fixist context and the advent of evolution sapped the foundations of this system, as was recognised long ago; the introduction of The Code of Nomenclature and Check-list of North American Birds Adopted by
3200-415: The group (although the peculiar Suctoria only have them for part of their life cycle ) and are variously used in swimming, crawling, attachment, feeding, and sensation. Ciliates are an important group of protists , common almost anywhere there is water—in lakes, ponds, oceans, rivers, and soils, including anoxic and oxygen-depleted habitats. About 4,500 unique free-living species have been described, and
3264-434: The hierarchy of taxa (hence, their ranks) does not necessarily reflect the hierarchy of clades . While older approaches to taxonomic classification were phenomenological, forming groups on the basis of similarities in appearance, organic structure and behavior, two important new methods developed in the second half of the 20th century changed drastically taxonomic practice. One is the advent of cladistics , which stemmed from
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#17327837900963328-496: The level of indentation reflects the rank, or absolute, in which various terms, such as species , genus , family , order , class , phylum , kingdom , and domain designate rank. This page emphasizes absolute ranks and the rank-based codes (the Zoological Code , the Botanical Code , the Code for Cultivated Plants , the Prokaryotic Code , and the Code for Viruses ) require them. However, absolute ranks are not required in all nomenclatural systems for taxonomists; for instance,
3392-555: The macronuclei disappear, and haploid micronuclei are exchanged over the bridge. In some ciliates (peritrichs, chonotrichs and some suctorians ), conjugating cells become permanently fused, and one conjugant is absorbed by the other. In most ciliate groups, however, the cells separate after conjugation, and both form new macronuclei from their micronuclei. Conjugation and autogamy are always followed by fission. In many ciliates, such as Paramecium , conjugating partners (gamonts) are similar or indistinguishable in size and shape. This
3456-405: The most basic (or important) is the species, but this opinion is not universally shared. Thus, species are not necessarily more sharply defined than taxa at any other rank, and in fact, given the phenotypic gaps created by extinction, in practice, the reverse is often the case. Ideally, a taxon is intended to represent a clade , that is, the phylogeny of the organisms under discussion, but this
3520-409: The most frequently advocated. Willi Hennig proposed it in 1966, but he concluded in 1969 that this system was unworkable and suggested dropping absolute ranks. However, the idea of ranking taxa using the age of origin (either as the sole criterion, or as one of the main ones) persists under the name of time banding, and is still advocated by several authors. For animals, at least the phylum rank
3584-586: The operational gene. Tetrahymena has about 6,000 IESs and about 15% of micronuclear DNA is eliminated during this process. The process is guided by small RNAs and epigenetic chromatin marks. In spirotrich ciliates (such as Oxytricha ), the process is even more complex due to "gene scrambling": the MDSs in the micronucleus are often in different order and orientation from that in the macronuclear gene, and so in addition to deletion, DNA inversion and translocation are required for "unscrambling". This process
3648-424: The other traditional hypotrichs, in the subclass Euplotia. Ciliate See text for subclasses. The ciliates are a group of alveolates characterized by the presence of hair-like organelles called cilia , which are identical in structure to eukaryotic flagella , but are in general shorter and present in much larger numbers, with a different undulating pattern than flagella. Cilia occur in all members of
3712-479: The phylum Chordata , and with them among all animals in the kingdom Animalia . Finally, at the highest rank all of these are grouped together with all other organisms possessing cell nuclei in the domain Eukarya . The International Code of Zoological Nomenclature defines rank as: "The level, for nomenclatural purposes, of a taxon in a taxonomic hierarchy (e.g. all families are for nomenclatural purposes at
3776-456: The potential number of extant species is estimated at 27,000–40,000. Included in this number are many ectosymbiotic and endosymbiotic species, as well as some obligate and opportunistic parasites . Ciliate species range in size from as little as 10 μm in some colpodeans to as much as 4 mm in length in some geleiids , and include some of the most morphologically complex protozoans. In most systems of taxonomy , " Ciliophora "
3840-455: The rank of species and above (but below genus) have a botanical name in two parts ( binary name ); all taxa below the rank of species have a botanical name in three parts (an infraspecific name ). To indicate the rank of the infraspecific name, a "connecting term" is needed. Thus Poa secunda subsp. juncifolia , where "subsp". is an abbreviation for "subspecies", is the name of a subspecies of Poa secunda . Hybrids can be specified either by
3904-653: The rank-based codes; because of this, some systematists prefer to call them nomenclatural ranks . In most cases, higher taxonomic groupings arise further back in time, simply because the most inclusive taxa necessarily appeared first. Furthermore, the diversity in some major taxa (such as vertebrates and angiosperms ) is better known that that of others (such as fungi , arthropods and nematodes ) not because they are more diverse than other taxa, but because they are more easily sampled and studied than other taxa, or because they attract more interest and funding for research. Of these many ranks, many systematists consider that
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#17327837900963968-468: The same rank, which lies between superfamily and subfamily)." Note that the discussions on this page generally assume that taxa are clades ( monophyletic groups of organisms), but this is required neither by the International Code of Zoological Nomenclature nor by the Botanical Code , and some experts on biological nomenclature do not think that this should be required, and in that case,
4032-485: The subgenus and species levels in taxa with many species, e.g. the genus Drosophila . (Note the potentially confusing use of "species group" as both a category of ranks as well as an unofficial rank itself. For this reason, Alain Dubois has been using the alternative expressions "nominal-series", "family-series", "genus-series" and "species-series" (among others) at least since 2000. ) At higher ranks (family and above)
4096-727: The works of the German entomologist Willi Hennig . Cladistics is a method of classification of life forms according to the proportion of characteristics that they have in common (called synapomorphies ). It is assumed that the higher the proportion of characteristics that two organisms share, the more recently they both came from a common ancestor. The second one is molecular systematics, based on genetic analysis , which can provide much additional data that prove especially useful when few phenotypic characters can resolve relationships, as, for instance, in many viruses , bacteria and archaea , or to resolve relationships between taxa that arose in
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