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79-491: The hybrid cultivar Ulmus × hollandica ' Cicestria' , commonly known as the ' Chichester Elm' , was cloned at the beginning of the 18th century from a tree growing at Chichester Hall, Rawreth , near Danbury , Essex , England, then the home of Thomas Holt White FRS , brother of the naturalist Gilbert White . The tree was first recorded by country parson and botanist Adam Buddle in south-east Essex in 1711, and appeared as U. cicestria in an 1801 catalogue. 'Cicestria'

158-475: A synthetic population . In horticulture , the term stable hybrid is used to describe an annual plant that, if grown and bred in a small monoculture free of external pollen (e.g., an air-filtered greenhouse) produces offspring that are "true to type" with respect to phenotype; i.e., a true-breeding organism. Hybridization can occur in the hybrid zones where the geographical ranges of species, subspecies, or distinct genetic lineages overlap. For example,

237-460: A bactrian camel and a dromedary . There are many examples of felid hybrids , including the liger . The oldest-known animal hybrid bred by humans is the kunga equid hybrid produced as a draft animal and status symbol 4,500 years ago in Umm el-Marra , present-day Syria . The first known instance of hybrid speciation in marine mammals was discovered in 2014. The clymene dolphin ( Stenella clymene )

316-633: A hybrid is the offspring resulting from combining the qualities of two organisms of different varieties , subspecies , species or genera through sexual reproduction . Generally, it means that each cell has genetic material from two different organisms, whereas an individual where some cells are derived from a different organism is called a chimera . Hybrids are not always intermediates between their parents such as in blending inheritance (a now discredited theory in modern genetics by particulate inheritance ), but can show hybrid vigor , sometimes growing larger or taller than either parent. The concept of

395-555: A bear shot by a hunter in the Northwest Territories confirmed the existence of naturally occurring and fertile grizzly–polar bear hybrids . Hybridization between reproductively isolated species often results in hybrid offspring with lower fitness than either parental. However, hybrids are not, as might be expected, always intermediate between their parents (as if there were blending inheritance), but are sometimes stronger or perform better than either parental lineage or variety,

474-508: A considerable seed yield advantage over open pollinated varieties. Hybrid seed dominates the commercial maize seed market in the United States, Canada and many other major maize-producing countries. In a hybrid, any trait that falls outside the range of parental variation (and is thus not simply intermediate between its parents) is considered heterotic. Positive heterosis produces more robust hybrids, they might be stronger or bigger; while

553-504: A cross between a female horse and a male donkey, and the hinny, a cross between a female donkey and a male horse. Pairs of complementary types like the mule and hinny are called reciprocal hybrids. Polar bears and brown bears are another case of a hybridizing species pairs, and introgression among non-sister species of bears appears to have shaped the Ursidae family tree. Among many other mammal crosses are hybrid camels , crosses between

632-561: A deer park, and any sucker growth is likely to have been grazed. The now-felled Chichester Elm in Old Foster Hill Road Cemetery, Bedford, is reported to produce root suckers. The tree was almost certainly named for Chichester Hall, where it originated. During the 16th century, the hall was the home of the Andrewes family, one of whom, Lancelot , was Bishop of Chichester from 1605 to 1609. Hybrid (biology) In biology ,

711-501: A degree that none of the originally genetically distinct population remains. In agriculture and animal husbandry , the Green Revolution 's use of conventional hybridization increased yields by breeding high-yielding varieties . The replacement of locally indigenous breeds, compounded with unintentional cross-pollination and crossbreeding (genetic mixing), has reduced the gene pools of various wild and indigenous breeds resulting in

790-602: A donkey as the father. A variety of mechanisms limit the success of hybridization, including the large genetic difference between most species. Barriers include morphological differences, differing times of fertility, mating behaviors and cues, and physiological rejection of sperm cells or the developing embryo. Some act before fertilization; others after it. In plants, some barriers to hybridization include blooming period differences, different pollinator vectors, inhibition of pollen tube growth, somatoplastic sterility, cytoplasmic-genic male sterility and structural differences of

869-548: A group of about 50 natural hybrids between Australian blacktip shark and the larger common blacktip shark was found by Australia's eastern coast in 2012. Russian sturgeon and American paddlefish were hybridized in captivity when sperm from the paddlefish and eggs from the sturgeon were combined, unexpectedly resulting in viable offspring. This hybrid is called a sturddlefish . The two genera Asymmetron and Branchiostoma are able to produce viable hybrid offspring, even if none have lived into adulthood so far, despite

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948-500: A hybrid is interpreted differently in animal and plant breeding, where there is interest in the individual parentage. In genetics , attention is focused on the numbers of chromosomes . In taxonomy, a key question is how closely related the parent species are. Species are reproductively isolated by strong barriers to hybridization, which include genetic and morphological differences, differing times of fertility, mating behaviors and cues, and physiological rejection of sperm cells or

1027-572: A large tree of upright growth with broad leaves, listing it separately from Huntingdon Elm and Ulmus 'Canadian Giant' . ... The Jebbs, my great-uncle Dick and my great-aunt Cara, lived at Springfield, at the southern end of the Backs , and their house looked across Queens' Green to the elms behind Queens' College. Two notable examples survive, courtesy of their isolation from diseased stock, at Queens' College, Cambridge , 44 m (144 ft) in height (2009). Annual inoculation with fungicide preserved

1106-439: A long time, both intentionally for purposes such as biological control , and unintentionally, as with accidental escapes of individuals. Introductions can drastically affect populations, including through hybridization. There is a kind of continuum with three semi-distinct categories dealing with anthropogenic hybridization: hybridization without introgression, hybridization with widespread introgression (backcrossing with one of

1185-494: A mate among the species that raised it, instead of the species of its biological parents. Cagebird breeders sometimes breed bird hybrids known as mules between species of finch , such as goldfinch × canary . Among amphibians, Japanese giant salamanders and Chinese giant salamanders have created hybrids that threaten the survival of Japanese giant salamanders because of competition for similar resources in Japan. Among fish,

1264-432: A phenomenon called heterosis, hybrid vigour, or heterozygote advantage . This is most common with plant hybrids. A transgressive phenotype is a phenotype that displays more extreme characteristics than either of the parent lines. Plant breeders use several techniques to produce hybrids, including line breeding and the formation of complex hybrids. An economically important example is hybrid maize (corn), which provides

1343-405: A species, such as between different breeds . Single cross hybrids result from the cross between two true-breeding organisms which produces an F1 hybrid (first filial generation). The cross between two different homozygous lines produces an F1 hybrid that is heterozygous ; having two alleles , one contributed by each parent and typically one is dominant and the other recessive . Typically,

1422-706: A tendency to regular drooping, and with less abundant foliage. A 1911 article in 'Historical Notes of Rillington and Scampston' described 'Scampstoniensis' as "remarkable for its size when mature, for its spreading habit, and its rough corky bark". 'Scampstoniensis' is not noted to have any resistance to Dutch elm disease . Loudon described the Scampston Elm, in a letter of 1836 to the Newcastle Courant , as "generally understood to have been extensively planted in Northumberland about 80 years ago". The Scampston Elm

1501-564: A third specimen at Chapelfield Gardens , Norwich , until it was blown over in a storm (January 2018). The Queens' College elms, believed to have been planted in the early 19th century, were reproduced in 2009 from cuttings by the National Trust as part of its Plant Conservation Programme, the young trees being distributed in 2017 to various Cambridge colleges and the University Botanic Garden, among other recipients. DNA testing by

1580-577: Is a hybrid of two Atlantic species, the spinner and striped dolphins . In 2019, scientists confirmed that a skull found 30 years earlier was a hybrid between the beluga whale and narwhal , dubbed the narluga . Hybridization between species is common in birds. Hybrid birds are purposefully bred by humans, but hybridization is also common in the wild. Waterfowl have a particularly high incidence of hybridization, with at least 60% of species known to produce hybrids with another species. Among ducks , mallards widely hybridize with many other species, and

1659-407: Is a hybridization test widely used in genetics to determine whether two separately isolated mutants that have the same (or similar) phenotype are defective in the same gene or in different genes (see Complementation (genetics) article). If a hybrid organism containing the genomes of two different mutant parental organisms displays a wild type phenotype, it is ordinarily considered that

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1738-571: Is a particularly common mechanism for speciation in plants, and is now known to be fundamental to the evolutionary history of plants. Plants frequently form polyploids , individuals with more than two copies of each chromosome. Whole genome doubling has occurred repeatedly in plant evolution. When two plant species hybridize, the hybrid may double its chromosome count by incorporating the entire nuclear genome of both parents, resulting in offspring that are reproductively incompatible with either parent because of different chromosome counts. Human impact on

1817-659: Is also more occasionally done in the livestock and pet trades; some well-known wild × domestic hybrids are beefalo and wolfdogs . Human selective breeding of domesticated animals and plants has also resulted in the development of distinct breeds (usually called cultivars in reference to plants); crossbreeds between them (without any wild stock ) are sometimes also imprecisely referred to as "hybrids". Hybrid humans existed in prehistory. For example, Neanderthals and anatomically modern humans are thought to have interbred as recently as 40,000 years ago. Mythological hybrids appear in human culture in forms as diverse as

1896-451: Is always sterile worker ants (and because ants are haplodiploid , unfertilized eggs become males). Without mating with males of the other species, the queens are unable to produce workers, and will fail to establish a colony of their own. Plant species hybridize more readily than animal species, and the resulting hybrids are fertile more often. Many plant species are the result of hybridization, combined with polyploidy , which duplicates

1975-547: Is derived from Latin hybrida , used for crosses such as of a tame sow and a wild boar. The term came into popular use in English in the 19th century, though examples of its use have been found from the early 17th century. Conspicuous hybrids are popularly named with portmanteau words , starting in the 1920s with the breeding of tiger–lion hybrids ( liger and tigon ). From the point of view of animal and plant breeders, there are several kinds of hybrid formed from crosses within

2054-514: Is susceptible to Dutch elm disease . Its Danbury-area provenance puts it in the Dengie elm group, considered by Oliver Rackham (1986) to have some degree of resilience. Examples of the tree were presented in 1711 by Adam Buddle to the Chelsea Physic Garden ; Buddle held a living at North Fambridge , not far from Rawreth. Adam Holt, relative of Thomas Holt, distributed the elms nationwide in

2133-427: Is that hybrid individuals can form a "bridge" transmitting potentially helpful genes from one species to another when the hybrid backcrosses with one of its parent species, a process called introgression . Hybrids can also cause speciation , either because the hybrids are genetically incompatible with their parents and not each other, or because the hybrids occupy a different niche than either parent. Hybridization

2212-475: Is the original Ulmus × hollandica ' Vegeta' ( Lindley , Hortus Cantabrigiensis , 1823), but suffered confusion with the later Huntingdon Elm cultivar by John Claudius Loudon who, without consulting Lindley, accorded the epithet 'Vegeta' to Huntingdon Elm in 1838, as he found the two indistinguishable. J. E. Little in The Journal of Botany (1923) agreed that Buddle's leaves-specimen of Chichester Elm in

2291-515: Is the proper time to give up on a population that is becoming a hybrid swarm, or to try and save the still existing pure individuals. Once a population becomes a complete mixture, the goal becomes to conserve those hybrids to avoid their loss. Conservationists treat each case on its merits, depending on detecting hybrids within the population. It is nearly impossible to formulate a uniform hybridization policy, because hybridization can occur beneficially when it occurs "naturally", and when hybrid swarms are

2370-608: The Hortus Botanicus Leiden , which had a specimen of 'Scampstoniensis' (see below). "From the Travemünder Nurseries we received an U. scampstoniensis , an elm with a beautiful pendulous shape," wrote Petzold, "that we distinguish from our U. montana Pendula. " 'Scampstoniensis' was said to droop its branches very distinctly and regularly, giving the tree a symmetrical form, as though it had been regularly trained and trimmed, unlike 'Camperdownii' , which had less of

2449-638: The Minotaur , blends of animals, humans and mythical beasts such as centaurs and sphinxes , and the Nephilim of the Biblical apocrypha described as the wicked sons of fallen angels and attractive women. Hybridization between species plays an important role in evolution, though there is much debate about its significance. Roughly 25% of plants and 10% of animals are known to form hybrids with at least one other species. One example of an adaptive benefit to hybridization

Ulmus × hollandica 'Cicestria' - Misplaced Pages Continue

2528-797: The Späth nursery and the Hesse Nursery of Weener , Germany, into the 1930s. Possibly only two specimens now survive in the UK, as grafted trees, in Brighton , England; see 'Notable trees' below. Another possible specimen stands in Fort Street, Cambridge, Waikato , New Zealand. A clone cultivated in China as Ulmus americana 'Pendula', top-grafted on Ulmus pumila stock, is neither Ulmus americana nor Scampston elm (formerly mis-named Ulmus americana 'Pendula'), but, in

2607-464: The sea urchin Strongylocentrotus purpuratus (female) and the sand dollar Dendraster excentricus (male). When two distinct types of organisms breed with each other, the resulting hybrids typically have intermediate traits (e.g., one plant parent has red flowers, the other has white, and the hybrid, pink flowers). Commonly, hybrids also combine traits seen only separately in one parent or

2686-438: The "suture region". It is at these regions that the subspecies were formed. Other hybrid zones have formed between described species of plants and animals. From the point of view of genetics, several different kinds of hybrid can be distinguished. A genetic hybrid carries two different alleles of the same gene , where for instance one allele may code for a lighter coat colour than the other. A structural hybrid results from

2765-406: The 1720s. Chichester Elms were planted at Woburn Abbey in the 1720–30s by Thomas Holt, who was agent for the estate, and are recorded in a photograph c.1915 as Ulmus vegeta , 'Huntingdon Elm' [ sic. ]; they no longer survive. Chichester Elm was marketed as U. cicestria in 1801 by nurseryman George Lindley of Catton, Norwich ; his 1815 catalogue lists the tree as U. Cicestriensis . Lindley's son,

2844-569: The 1890 Sempervirens article. The c.1920 tree, though mature, closely resembles the 1859 illustration of a young 'Scampstoniensis' in New York, while a 1931 Ulmus americana pendula herbarium specimen from Leiden matches the 1902 Späth 'Scampstoniensis' specimens held in RBGE. The 1890 article had expressed doubts about the name Ulmus americana Pendula ; the c.1920 photograph labels the tree U. scabra [our U. glabra ] pendula , despite its differences from

2923-513: The Chichester Elm as U. vegeta . The claimed North American source of the tree in later 19th-century catalogues almost certainly arose from Loudon's lumping together of Chichester Elm and Huntingdon Elm, for which he noted the synonym 'American Elm' adopted by some nurserymen (owing to the similarity in shape) and the Scampston Elm , with its supposed American provenance. There is no record of

3002-503: The F1 generation is also phenotypically homogeneous, producing offspring that are all similar to each other. Double cross hybrids result from the cross between two different F1 hybrids (i.e., there are four unrelated grandparents). Three-way cross hybrids result from the cross between an F1 hybrid and an inbred line. Triple cross hybrids result from the crossing of two different three-way cross hybrids. Top cross (or "topcross") hybrids result from

3081-531: The Huntingdon Elm. The Rev. Adam Buddle originally identified the tree as 'a broad-leaved smooth Wych Elm' that grew 'plentifully about Danbury'. A distinguishing feature of 'Vegeta', according to Schneider (1906) and Mitchell (1974), is that the leaf margins to right and left of the petiole start from a vein, not from the midrib. This feature appears in the Queens' College Chichester leaves (see autumn leaves from

3160-721: The Scampston Elm" was described at the Royal Victoria Park, Bath , in 1857 and 1902, where was listed as U. montana Glabra [:'smooth'(-leaved)] microphylla pendula . One tree was planted in 1896 as U. glabra scampstoniensis at the Dominion Arboretum , Ottawa , Canada . Three specimens supplied by the Späth nursery of Berlin to the Royal Botanic Garden Edinburgh in 1902 as U. glabra [:'smooth'(-leaved)] Scampstoniensis may survive in Edinburgh , as it

3239-671: The Sloane Herbarium seemed to be the same cultivar as Huntingdon Elm: "If so, this elm [Chichester] was in existence and mature some years before the reputed raising of the Huntingdon Elm by Wood of Huntingdon 'about 1746'." Lindley in A Synopsis of British Flora, arranged according to the Natural Order (1829) appeared to distinguish "the Chichester elm" from "the Giant elm", 'Canadian Giant' . A very tall tree, with foliage similar to that of

Ulmus × hollandica 'Cicestria' - Misplaced Pages Continue

3318-511: The butterfly Limenitis arthemis has two major subspecies in North America, L. a. arthemis (the white admiral) and L. a. astyanax (the red-spotted purple). The white admiral has a bright, white band on its wings, while the red-spotted purple has cooler blue-green shades. Hybridization occurs between a narrow area across New England, southern Ontario, and the Great Lakes,

3397-486: The case of the majority of photographs on the Plant Photo Bank of China, a weeping form of U. glabra Huds. , probably 'Camperdownii' . A weeping elm in the Hortus Botanicus Leiden was described there by the curator in 1890 in a Sempervirens article as an Ulmus americana Pendula , one of the synonyms of 'Scampstoniensis'. It was carefully distinguished by him from two forms of weeping wych elm nearby, and

3476-426: The chromosomes. A few animal species are the result of hybridization. The Lonicera fly is a natural hybrid. The American red wolf appears to be a hybrid of the gray wolf and the coyote , although its taxonomic status has been a subject of controversy. The European edible frog is a semi-permanent hybrid between pool frogs and marsh frogs ; its population requires the continued presence of at least one of

3555-539: The chromosomes. Chromosome duplication allows orderly meiosis and so viable seed can be produced. Plant hybrids are generally given names that include an "×" (not in italics), such as Platanus × hispanica for the London plane, a natural hybrid of P. orientalis (oriental plane) and P. occidentalis (American sycamore). The parent's names may be kept in their entirety, as seen in Prunus persica × Prunus americana , with

3634-481: The common pheasant and hen golden pheasant ( Chrysolophus pictus ). Spurs are absent in hybrids of the former type, although present in both parents. Hybridization is greatly influenced by human impact on the environment, through effects such as habitat fragmentation and species introductions. Such impacts make it difficult to conserve the genetics of populations undergoing introgressive hybridization . Humans have introduced species worldwide to environments for

3713-400: The crossing of a top quality or pure-bred male and a lower quality female, intended to improve the quality of the offspring, on average. Population hybrids result from the crossing of plants or animals in one population with those of another population. These include interspecific hybrids or crosses between different breeds. In biology, the result of crossing of two populations is called

3792-444: The developing embryo . Some act before fertilization and others after it. Similar barriers exist in plants, with differences in flowering times, pollen vectors, inhibition of pollen tube growth, somatoplastic sterility, cytoplasmic-genic male sterility and the structure of the chromosomes. A few animal species and many plant species, however, are the result of hybrid speciation , including important crop plants such as wheat , where

3871-407: The diverse Heliconius butterflies , but that is disputed. The two closely related harvester ant species Pogonomyrmex barbatus and Pogonomyrmex rugosus have evolved to depend on hybridization. When a queen fertilizes her eggs with sperm from males of her own species, the offspring is always new queens. And when she fertilizes the eggs with sperm from males of the other species, the offspring

3950-413: The doubling of chromosome sets, causing immediate genetic isolation. Hybridization may be important in speciation in some plant groups. However, homoploid hybrid speciation (not increasing the number of sets of chromosomes) may be rare: by 1997, only eight natural examples had been fully described. Experimental studies suggest that hybridization offers a rapid route to speciation, a prediction confirmed by

4029-597: The eminent botanist John Lindley FRS, had worked in Cambridge as assistant to John Henslow , later Professor of Botany at the University, helping him lay out and catalogue the Cambridge University Botanic Garden . It is possible that the tree owes its Cambridge introduction to John Lindley, whose 1823 revision of Donn's (d. 1813) Hortus Cantabrigiensis contains the first reference, bestowed by him, to

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4108-611: The environment has resulted in an increase in the interbreeding between regional species, and the proliferation of introduced species worldwide has also resulted in an increase in hybridization. This has been referred to as genetic pollution out of concern that it may threaten many species with extinction. Similarly, genetic erosion from monoculture in crop plants may be damaging the gene pools of many species for future breeding. The conservation impacts of hybridization between species are highly debated. While hybridization could potentially threaten rare species or lineages by "swamping"

4187-429: The fact that early generation hybrids and ancient hybrid species have matching genomes, meaning that once hybridization has occurred, the new hybrid genome can remain stable. Many hybrid zones are known where the ranges of two species meet, and hybrids are continually produced in great numbers. These hybrid zones are useful as biological model systems for studying the mechanisms of speciation. Recently DNA analysis of

4266-530: The female parent's name given first, or if not known, the parent's names given alphabetically. Ulmus %27Scampstoniensis%27 Georg Dieck of the National Arboretum in Zöschen , Germany, considered 'Scampstoniensis' a synonym of Ulmus scabra Serpentina [see U. × hollandica 'Serpentina' ], a view rejected by Petzold , who in his Arboretum Muscaviense listed 'Scampstoniensis' separately, and by

4345-529: The forestry research team at Roslin in 2013 confirmed that the supposed Chichester Elms in Old Foster Hill Road Cemetery, Bedford (died c.2015), and in Norwich were the same clone as the Queens' trees. The 2013 test did not, however, systematically compare Chichester Elm DNA with that of supposed Huntingdon Elm (it did not include a younger nursery-sourced "Huntingdon" as a control), though an old 'Vegeta'-type hybrid from Castle Acre Priory , Norfolk (girth 4.5 m),

4424-560: The fusion of gametes that have differing structure in at least one chromosome, as a result of structural abnormalities . A numerical hybrid results from the fusion of gametes having different haploid numbers of chromosomes . A permanent hybrid results when only the heterozygous genotype occurs, as in Oenothera lamarckiana , because all homozygous combinations are lethal. In the early history of genetics, Hugo de Vries supposed these were caused by mutation . Genetic complementation

4503-507: The genetic relationships between ducks are further complicated by the widespread gene flow between wild and domestic mallards. One of the most common interspecific hybrids in geese occurs between Greylag and Canada geese ( Anser anser x Branta canadensis ). One potential mechanism for the occurrence of hybrids in these geese is interspecific nest parasitism , where an egg is laid in the nest of another species to be raised by non-biological parents. The chick imprints upon and eventually seeks

4582-630: The genetically "pure" individuals with hybrids, hybridization could also save a rare lineage from extinction by introducing genetic diversity. It has been proposed that hybridization could be a useful tool to conserve biodiversity by allowing organisms to adapt, and that efforts to preserve the separateness of a "pure" lineage could harm conservation by lowering the organisms' genetic diversity and adaptive potential, particularly in species with low populations. While endangered species are often protected by law, hybrids are often excluded from protection, resulting in challenges to conservation. The term hybrid

4661-401: The hybrids are more fit and have breeding advantages over the indigenous ecotype or species. These hybridization events can result from the introduction of non-native genotypes by humans or through habitat modification, bringing previously isolated species into contact. Genetic mixing can be especially detrimental for rare species in isolated habitats, ultimately affecting the population to such

4740-469: The largest tree of any kind in Britain. However, as Elwes pointed out, its calculated age would place its planting in the late 17th or early 18th century, long before the introduction of the Huntingdon Elm, making the tree in question more likely to be a Chichester Elm. A second tree nearby, described by Elwes as "similar in habit and foliage" and 130 feet (40 m) tall by 23 feet (7.0 m) in girth in 1912,

4819-400: The loss of genetic diversity . Since the indigenous breeds are often well-adapted to local extremes in climate and have immunity to local pathogens, this can be a significant genetic erosion of the gene pool for future breeding. Therefore, commercial plant geneticists strive to breed "widely adapted" cultivars to counteract this tendency. Familiar examples of equid hybrids are the mule,

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4898-452: The number of chromosomes has been doubled. A form of often intentional human-mediated hybridization is the crossing of wild and domesticated species. This is common in both traditional horticulture and modern agriculture ; many commercially useful fruits, flowers, garden herbs, and trees have been produced by hybridization. One such flower, Oenothera lamarckiana , was central to early genetics research into mutationism and polyploidy. It

4977-704: The old trees, in gallery) and is frequently present in classic chalice -shaped 'Vegeta' elsewhere, assumed to be Huntingdon (see 'Description' gallery, 'Vegeta' ). If, however, the feature distinguishes Chichester from Huntingdon, the former may be more common in cultivation than currently believed, having over time been mis-called "Huntingdon". Leaves from Hinchingbrooke Park, the stated source of Huntingdon, collected by Heybroek in 1960 do not show this feature, nor do some old 'Vegeta' cultivars in Oxford and Edinburgh (see ' 'Vegeta'-like cultivars' in Huntingdon article). The tree

5056-420: The only remaining evidence of prior species, they need to be conserved as well. Regionally developed ecotypes can be threatened with extinction when new alleles or genes are introduced that alter that ecotype. This is sometimes called genetic mixing. Hybridization and introgression, which can happen in natural and hybrid populations, of new genetic material can lead to the replacement of local genotypes if

5135-438: The other (e.g., a bird hybrid might combine the yellow head of one parent with the orange belly of the other). Interspecific hybrids are bred by mating individuals from two species, normally from within the same genus. The offspring display traits and characteristics of both parents, but are often sterile , preventing gene flow between the species. Sterility is often attributed to the different number of chromosomes between

5214-573: The parent species), and hybrid swarms (highly variable populations with much interbreeding as well as backcrossing with the parent species). Depending on where a population falls along this continuum, the management plans for that population will change. Hybridization is currently an area of great discussion within wildlife management and habitat management. Global climate change is creating other changes such as difference in population distributions which are indirect causes for an increase in anthropogenic hybridization. Conservationists disagree on when

5293-532: The parent species. Cave paintings indicate that the European bison is a natural hybrid of the aurochs and the steppe bison . Plant hybridization is more commonplace compared to animal hybridization. Many crop species are hybrids, including notably the polyploid wheats : some have four sets of chromosomes (tetraploid) or six (hexaploid), while other wheat species have (like most eukaryotic organisms) two sets ( diploid ), so hybridization events likely involved

5372-506: The parents' common ancestor living tens of millions of years ago. Among insects, so-called killer bees were accidentally created during an attempt to breed a strain of bees that would both produce more honey and be better adapted to tropical conditions. It was done by crossing a European honey bee and an African bee . The Colias eurytheme and C. philodice butterflies have retained enough genetic compatibility to produce viable hybrid offspring. Hybrid speciation may have produced

5451-637: The point of view of taxonomy , hybrids differ according to their parentage. Hybrids between different subspecies (such as between the dog and Eurasian wolf ) are called intra-specific hybrids. Interspecific hybrids are the offspring from interspecies mating ; these sometimes result in hybrid speciation. Intergeneric hybrids result from matings between different genera, such as between sheep and goats . Interfamilial hybrids, such as between chickens and guineafowl or pheasants , are reliably described but extremely rare. Interordinal hybrids (between different orders) are few, but have been engineered between

5530-470: The term negative heterosis refers to weaker or smaller hybrids. Heterosis is common in both animal and plant hybrids. For example, hybrids between a lion and a tigress (" ligers ") are much larger than either of the two progenitors, while " tigons " (lioness × tiger) are smaller. Similarly, the hybrids between the common pheasant ( Phasianus colchicus ) and domestic fowl ( Gallus gallus ) are larger than either of their parents, as are those produced between

5609-503: The tree's introduction to North America, but both an U. montana vegeta and an U. montana Huntingdoni were planted at the Dominion Arboretum , Ottawa , Canada, in 1893, as distinct clones; it is possible that the first was Chichester Elm. Chichester Elm is known to have been marketed in Victoria , Australia, from 1873. In the early 20th century the Gembrook or Nobelius Nursery described it as

5688-400: The two parental mutant organisms are defective in different genes. If the hybrid organism displays a distinctly mutant phenotype, the two mutant parental organisms are considered to be defective in the same gene. However, in some cases the hybrid organism may display a phenotype that is only weakly (or partially) wild-type, and this may reflect intragenic (interallelic) complementation. From

5767-462: The two species. For example, donkeys have 62 chromosomes , horses have 64 chromosomes, and mules or hinnies have 63 chromosomes. Mules, hinnies, and other normally sterile interspecific hybrids cannot produce viable gametes, because differences in chromosome structure prevent appropriate pairing and segregation during meiosis , meiosis is disrupted, and viable sperm and eggs are not formed. However, fertility in female mules has been reported with

5846-740: The two weeping wych clones. The herbarium of the Naturalis Biodiversity Center in Leiden holds leaf specimens labelled " U. carpinifolia 'Pendula' (formerly called U. glabra Hudson 'Scampstoniensis')", from a tree in the Wageningen Arboretum. The possible UK TROBI Champions grow in Woodvale Cemetery, Brighton, perhaps planted in 1851; two grafted trees, survivors of some ten c.1980, measuring 26 m high by 73 cm d.b.h. , and 22 m by 70 cm, in 2002. One of

5925-502: Was confirmed by Nellie Bancroft in a Gardener's Chronicle article in 1934 as a 'Vegeta'-type hybrid; it was propagated by Heybroek in 1958 and cultivated at the Baarn elm research institute as clone P41. The tree survived until the 1960s. Like the Queens' trees in Cambridge, the Magdalen trees in Oxford were not observed to produce root suckers . The Grove at Magdalen, however, has long been

6004-594: Was in cultivation on both sides of the Atlantic in the 19th century and was occasionally referred to as Ulmus americana pendula . (Other European elms described as 'American' by various nurseries include 'Vegeta' , 'Lutescens' , and 'Nana' . ) The American horticulturalist Frank Jesup Scott in The Art of Beautifying Suburban Home Grounds of Small Extent (1870) described how two "Scampston elms" could be pruned and trained to form an archway of weeping elm. "A weeping variety of

6083-537: Was said to produce, in addition, vigorous ascending branches that needed regular pruning to maintain a tidy weeping shape. Three weeping elms were later photographed in the Hortus c.1920, two of them forms of weeping wych, the third a semi-weeping elm with smaller leaves and numerous long shoots, many ascending, that appears at one time to have been pruned: by process of elimination, the Ulmus americana Pendula ('Scampstoniensis') of

6162-504: Was tested and found to be a different clone from Chichester. An elm in The Grove at Magdalen College, Oxford , photographed by Henry Taunt in 1900, long believed to be a wych elm before being identified by Henry John Elwes as a 'Vegeta'-type hybrid, was for a time the largest elm known in Britain before it was blown down in 1911 (see under U. × hollandica ). It measured 44 m tall, its trunk at breast height 2.6 m in diameter,

6241-695: Was the practice of the Garden to distribute trees about the city (viz. the Wentworth Elm ). A specimen obtained from Späth before 1914 as U. glabra scampstoniensis , and planted in 1916, stood in the Ryston Hall arboretum, Norfolk , in the early 20th century. Elwes saw the decayed stump of the original tree at Scampston Hall , by which time (1913) the tree was no longer known to be in cultivation in nurseries in England. 'Scampstoniensis' continued to be distributed by

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