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biology Biology is the scientific study of life. It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field. For instance, all organisms are made up of cells that process hereditary ...
, a hybrid is the offspring resulting from combining the qualities of two organisms of different breeds, varieties, species or genera through sexual reproduction. Hybrids are not always intermediates between their parents (such as in
blending inheritance Blending may refer to: * The process of mixing in process engineering * Mixing paints to achieve a greater range of colors * Blending (alcohol production), a technique to produce alcoholic beverages by mixing different brews * Blending (linguis ...
), but can show hybrid vigor, sometimes growing larger or taller than either parent. The concept of 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 In biology, a species is the basic unit of Taxonomy (biology), classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of ...
are. Species are
reproductively isolated The mechanisms of reproductive isolation are a collection of evolutionary mechanisms, behaviors and physiological processes critical for speciation. They prevent members of different species from producing offspring, or ensure that any offspring ...
by strong barriers to hybridisation, which include genetic and morphological differences, differing times of fertility, mating behaviors and cues, and physiological rejection of sperm cells or the developing embryo. Some act before
fertilization Fertilisation or fertilization (see spelling differences), also known as generative fertilisation, syngamy and impregnation, is the fusion of gametes to give rise to a new individual organism or offspring and initiate its development. Proce ...
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 Hybrid speciation is a form of speciation where hybridization between two different species leads to a new species, reproductively isolated from the parent species. Previously, reproductive isolation between two species and their parents was tho ...
, including important crop plants such as wheat, where the number of chromosomes has been doubled. Human impact on 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 hybridisation. This
genetic mixing Genetic pollution is a controversial term for uncontrolled gene flow into wild populations. It is defined as "the dispersal of contaminated altered genes from genetically engineered organisms to natural organisms, esp. by cross-pollination", but ...
may threaten many species with extinction, while genetic erosion from
monoculture In agriculture, monoculture is the practice of growing one crop species in a field at a time. Monoculture is widely used in intensive farming and in organic farming: both a 1,000-hectare/ acre cornfield and a 10-ha/acre field of organic kale ...
in crop plants may be damaging the gene pools of many species for future breeding. A form of often intentional human-mediated hybridisation is the crossing of wild and domesticated species. This is common in both traditional horticulture and modern
agriculture Agriculture or farming is the practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that enabled people to ...
; many commercially useful fruits, flowers, garden herbs, and trees have been produced by hybridisation. One such flower, ''
Oenothera lamarckiana ''Oenothera glazioviana'' is a species of flowering plant in the evening primrose family known by the common names large-flowered evening-primrose and redsepal evening primrose. ''Oenothera lamarckiana'' was formerly believed to be a different s ...
'', was central to early genetics research into
mutationism Mutationism is one of several alternatives to evolution by natural selection that have existed both before and after the publication of Charles Darwin's 1859 book ''On the Origin of Species''. In the theory, mutation was the source of novelty, c ...
and polyploidy. It is also more occasionally done in the livestock and pet trades; some well-known wild × domestic hybrids are
beefalo Beefalo constitute a hybrid offspring of domestic cattle (''Bos taurus''), usually a male in managed breeding programs, and the American bison (''Bison bison''), usually a female in managed breeding programs. The breed was created to combine the ...
and
wolfdog A wolfdog is a canine produced by the mating of a domestic dog (''Canis familiaris'') with a gray wolf (''Canis lupus''), eastern wolf (''Canis lycaon''), red wolf (''Canis rufus''), or Ethiopian wolf (''Canis simensis'') to produce a hybr ...
s. Human selective breeding of
domesticated animals This page gives a list of domesticated animals, also including a list of animals which are or may be currently undergoing the process of domestication and animals that have an extensive relationship with humans beyond simple predation. This includ ...
and
plants Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all current definitions of Plantae exclude ...
has resulted in the development of distinct
breeds A breed is a specific group of domestic animals having homogeneous appearance ( phenotype), homogeneous behavior, and/or other characteristics that distinguish it from other organisms of the same species. In literature, there exist several slig ...
(usually called cultivars in reference to plants);
crossbreed A crossbreed is an organism with purebred parents of two different breeds, varieties, or populations. ''Crossbreeding'', sometimes called "designer crossbreeding", is the process of breeding such an organism, While crossbreeding is used to main ...
s between them (without any wild stock) are sometimes also imprecisely referred to as "hybrids". Hybrid humans existed in prehistory. For example,
Neanderthals Neanderthals (, also ''Homo neanderthalensis'' and erroneously ''Homo sapiens neanderthalensis''), also written as Neandertals, are an extinct species or subspecies of archaic humans who lived in Eurasia until about 40,000 years ago. While ...
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 the
Minotaur In Greek mythology, the Minotaur ( , ;. grc, ; in Latin as ''Minotaurus'' ) is a mythical creature portrayed during classical antiquity with the head and tail of a bull and the body of a man or, as described by Roman poet Ovid, a being "pa ...
, blends of animals, humans and mythical beasts such as centaurs and sphinxes, and the
Nephilim The Nephilim (; ''Nəfīlīm'') are mysterious beings or people in the Hebrew Bible who are large and strong. The word ''Nephilim'' is loosely translated as ''giants'' in some translations of the Hebrew Bible, but left untranslated in others. ...
of the
Biblical apocrypha The biblical apocrypha (from the grc, ἀπόκρυφος, translit=apókruphos, lit=hidden) denotes the collection of apocryphal ancient books thought to have been written some time between 200 BC and AD 400. The Roman Catholic, Eastern Or ...
described as the wicked sons of fallen angels and attractive women.


Etymology

The term hybrid is derived from Latin ', 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).


As seen by different disciplines


Animal and plant breeding

From the point of view of animal and plant breeders, there are several kinds of hybrid formed from crosses within a species, such as between different
breeds A breed is a specific group of domestic animals having homogeneous appearance ( phenotype), homogeneous behavior, and/or other characteristics that distinguish it from other organisms of the same species. In literature, there exist several slig ...
. Single cross hybrids result from the cross between two true-breeding organisms which produces an
F1 hybrid An F1 hybrid (also known as filial 1 hybrid) is the first filial generation of offspring of distinctly different parental types. F1 hybrids are used in genetics, and in selective breeding, where the term F1 crossbreed may be used. The term is somet ...
(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 In genetics, dominance is the phenomenon of one variant (allele) of a gene on a chromosome masking or overriding the effect of a different variant of the same gene on the other copy of the chromosome. The first variant is termed dominant and t ...
. Typically, the F1 generation is also
phenotypically In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology or physical form and structure, its developmental processes, its biochemical and physiological proper ...
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 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 horticulture, the term stable hybrid is used to describe an
annual plant An annual plant is a plant that completes its life cycle, from germination to the production of seeds, within one growing season, and then dies. The length of growing seasons and period in which they take place vary according to geographical l ...
that, if grown and bred in a small
monoculture In agriculture, monoculture is the practice of growing one crop species in a field at a time. Monoculture is widely used in intensive farming and in organic farming: both a 1,000-hectare/ acre cornfield and a 10-ha/acre field of organic kale ...
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.


Biogeography

Hybridisation can occur in the
hybrid zone A hybrid zone exists where the ranges of two interbreeding species or diverged intraspecific lineages meet and cross-fertilize. Hybrid zones can form ''in situ'' due to the evolution of a new lineage but generally they result from secondary contact ...
s where the geographical ranges of species, subspecies, or distinct genetic lineages overlap. For example, the butterfly ''
Limenitis arthemis ''Limenitis arthemis,'' the red-spotted purple or white admiral, is a North American butterfly species in the cosmopolitan genus '' Limenitis''. It has been studied for its evolution of mimicry, and for the several stable hybrid wing patterns w ...
'' 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. Hybridisation occurs between a narrow area across New England, southern Ontario, and the Great Lakes, 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.


Genetics

From the point of view of genetics, several different kinds of hybrid can be distinguished. A genetic hybrid carries two different
allele An allele (, ; ; modern formation from Greek ἄλλος ''állos'', "other") is a variation of the same sequence of nucleotides at the same place on a long DNA molecule, as described in leading textbooks on genetics and evolution. ::"The chro ...
s of the same gene, where for instance one allele may code for a lighter coat colour than the other. A structural hybrid results from 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 The genotype of an organism is its complete set of genetic material. Genotype can also be used to refer to the alleles or variants an individual carries in a particular gene or genetic location. The number of alleles an individual can have in a ...
occurs, as in ''
Oenothera lamarckiana ''Oenothera glazioviana'' is a species of flowering plant in the evening primrose family known by the common names large-flowered evening-primrose and redsepal evening primrose. ''Oenothera lamarckiana'' was formerly believed to be a different s ...
'', because all homozygous combinations are lethal. In the early history of genetics, Hugo de Vries supposed these were caused by mutation.


Taxonomy

From the point of view of taxonomy, hybrids differ according to their parentage. Hybrids between different subspecies (such as between the
Dog The dog (''Canis familiaris'' or ''Canis lupus familiaris'') is a domesticated descendant of the wolf. Also called the domestic dog, it is derived from the extinct Pleistocene wolf, and the modern wolf is the dog's nearest living relative. ...
and Eurasian wolf) are called intra-specific hybrids. Interspecific hybrids are the offspring from
interspecies mating Non-reproductive sexual behavior consists of sexual activities animals participate in that do not lead to the reproduction of the species. Although procreation continues to be the primary explanation for sexual behavior in animals, recent obser ...
; 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 the sea urchin ''
Strongylocentrotus purpuratus ''Strongylocentrotus purpuratus'', the purple sea urchin, lives along the eastern edge of the Pacific Ocean extending from Ensenada, Mexico, to British Columbia, Canada. This sea urchin species is deep purple in color, and lives in lower int ...
'' (female) and the
sand dollar Sand dollars (also known as a sea cookie or snapper biscuit in New Zealand, or pansy shell in South Africa) are species of flat, burrowing sea urchins belonging to the order Clypeasteroida. Some species within the order, not quite as flat, are ...
''
Dendraster excentricus ''Dendraster excentricus'', also known as the eccentric sand dollar, sea-cake, biscuit-urchin, western sand dollar, or Pacific sand dollar, is a species of sand dollar in the family Dendrasteridae. It is a flattened, burrowing sea urchin found ...
'' (male).


Biology


Expression of parental traits

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 the other (e.g., a
bird hybrid A bird hybrid is a bird that has two different species as parents. The resulting bird can present with any combination of characteristics from the parent species, from totally identical to completely different. Usually, the bird hybrid shows inter ...
might combine the yellow head of one parent with the orange belly of the other).


Mechanisms of reproductive isolation

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 the two species. For example, donkeys have 62
chromosomes A chromosome is a long DNA molecule with part or all of the genetic material of an organism. In most chromosomes the very long thin DNA fibers are coated with packaging proteins; in eukaryotic cells the most important of these proteins are ...
, 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 a donkey as the father. A variety of mechanisms limit the success of hybridisation, 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.Strickberger, M. 1978. ''Genética''. Omega, Barcelona, España, p.: 874–879. .Futuyma, D. 1998. ''Evolutionary biology'' (3ª edición). Sinauer, Sunderland. In plants, some barriers to hybridisation include blooming period differences, different pollinator vectors, inhibition of pollen tube growth, somatoplastic sterility, cytoplasmic-genic male sterility and structural differences of the chromosomes.


Speciation

A few animal species are the result of hybridization. The
Lonicera fly The ''Lonicera'' fly, a hybrid in the genus ''Rhagoletis'', is a North American fruit fly of the family Tephritidae. Its larvae feed on the berries of species of introduced honeysuckle (''Lonicera'') that were brought to America within the las ...
is a natural hybrid. The American
red wolf The red wolf (''Canis rufus'') is a canine native to the southeastern United States. Its size is intermediate between the coyote (''Canis latrans'') and gray wolf (''Canis lupus''). The red wolf's taxonomic classification as being a separate s ...
appears to be a hybrid of the
gray wolf The wolf (''Canis lupus''; plural, : wolves), also known as the gray wolf or grey wolf, is a large Canis, canine native to Eurasia and North America. More than thirty subspecies of Canis lupus, subspecies of ''Canis lupus'' have been reco ...
and the
coyote The coyote (''Canis latrans'') is a species of canine native to North America. It is smaller than its close relative, the wolf, and slightly smaller than the closely related eastern wolf and red wolf. It fills much of the same ecological n ...
, 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 the parent species. Cave paintings indicate that the European bison is a natural hybrid of the
aurochs The aurochs (''Bos primigenius'') ( or ) is an extinct cattle species, considered to be the wild ancestor of modern domestic cattle. With a shoulder height of up to in bulls and in cows, it was one of the largest herbivores in the Holocene ...
and the
steppe bison The steppe bisonSeveral literatures address the species as ''primeval bison''. or steppe wisent (''Bison'' ''priscus'')
– Y ...
. Plant hybridization is more commonplace compared to animal hybridization. Many
crop A crop is a plant that can be grown and harvested extensively for profit or subsistence. When the plants of the same kind are cultivated at one place on a large scale, it is called a crop. Most crops are cultivated in agriculture or hydroponi ...
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 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 8 natural examples had been fully described. Experimental studies suggest that hybridization offers a rapid route to speciation, a prediction confirmed by 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 zone A hybrid zone exists where the ranges of two interbreeding species or diverged intraspecific lineages meet and cross-fertilize. Hybrid zones can form ''in situ'' due to the evolution of a new lineage but generally they result from secondary contact ...
s 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 a bear shot by a hunter in the
North West Territories The Northwest Territories (abbreviated ''NT'' or ''NWT''; french: Territoires du Nord-Ouest, formerly ''North-Western Territory'' and ''North-West Territories'' and namely shortened as ''Northwest Territory'') is a federal territory of Canada. ...
confirmed the existence of naturally-occurring and fertile grizzly–polar bear hybrids.


Hybrid vigour

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, a phenomenon called heterosis, hybrid vigour, or heterozygote advantage. This is most common with plant hybrids. A
transgressive phenotype In genetics, transgressive segregation is the formation of extreme phenotypes, or transgressive phenotypes, observed in segregated hybrid populations compared to phenotypes observed in the parental lines. The appearance of these transgressive (extr ...
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 a considerable seed yield advantage over open pollinated varieties.
Hybrid seed In agriculture and gardening, hybrid seed is produced by cross-pollinated plants. Hybrid seed production is predominant in modern agriculture and home gardening. It is one of the main contributors to the dramatic rise in agricultural output during ...
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 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 The liger is a hybrid offspring of a male lion (''Panthera leo'') and a female tiger (''Panthera tigris''). The liger has parents in the same genus but of different species. The liger is distinct from the similar hybrid called the tigon, and ...
") are much larger than either of the two progenitors, while "
tigons A tigon (), tiglon () (portmanteau of ''tiger'' and ''lion''), or tion () is the hybrid offspring of a male tiger (''Panthera tigris'') and a female lion (''Panthera leo'').
" (lioness × tiger) are smaller. Similarly, the hybrids between the common pheasant (''
Phasianus colchicus The common pheasant (''Phasianus colchicus'') is a bird in the pheasant family (Phasianidae). The genus name comes from Latin ''phasianus'', "pheasant". The species name ''colchicus'' is Latin for "of Colchis" (modern day Georgia), a country on ...
'') and domestic fowl (''
Gallus gallus The red junglefowl (''Gallus gallus'') is a tropical bird in the family Phasianidae. It ranges across much of Southeast Asia and parts of South Asia. It was formerly known as the Bankiva or Bankiva Fowl. It is the species that gave rise to the ...
'') are larger than either of their parents, as are those produced between the common pheasant and hen golden pheasant (''
Chrysolophus pictus The golden pheasant (''Chrysolophus pictus''), also known as the Chinese pheasant, and rainbow pheasant, is a gamebird of the order Galliformes (gallinaceous birds) and the family Phasianidae (pheasants). The genus name is from Ancient Greek ' ...
''). Spurs are absent in hybrids of the former type, although present in both parents.


Human influence


Anthropogenic hybridization

Hybridization is greatly influenced by human impact on the environment, through effects such as
habitat fragmentation Habitat fragmentation describes the emergence of discontinuities (fragmentation) in an organism's preferred environment (habitat), causing population fragmentation and ecosystem decay. Causes of habitat fragmentation include geological process ...
and species introductions. Such impacts make it difficult to conserve the genetics of populations undergoing
introgressive hybridization Introgression, also known as introgressive hybridization, in genetics is the transfer of genetic material from one species into the gene pool of another by the repeated backcrossing of an interspecific hybrid with one of its parent species. Introg ...
. Humans have introduced species worldwide to environments for a long time, both intentionally for purposes such as
biological control Biological control or biocontrol is a method of controlling pests, such as insects, mites, weeds, and plant diseases, using other organisms. It relies on predation, parasitism, herbivory, or other natural mechanisms, but typically also invo ...
, and unintentionally, as with accidental escapes of individuals. Introductions can drastically affect populations, including through hybridization.


Management

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 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 Wildlife management is the management process influencing interactions among and between wildlife, its habitats and people to achieve predefined impacts. It attempts to balance the needs of wildlife with the needs of people using the best availabl ...
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 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 the only remaining evidence of prior species, they need to be conserved as well.


Genetic mixing and extinction

Regionally developed
ecotype In evolutionary ecology, an ecotype,Greek: ''οίκος'' = home and ''τύπος'' = type, coined by Göte Turesson in 1922 sometimes called ecospecies, describes a genetically distinct geographic variety, population, or race within a species ...
s 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 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 a degree that none of the originally genetically distinct population remains.


Effect on biodiversity and food security

In agriculture and
animal husbandry Animal husbandry is the branch of agriculture concerned with animals that are raised for meat, fibre, milk, or other products. It includes day-to-day care, selective breeding, and the raising of livestock. Husbandry has a long history, startin ...
, the
Green Revolution The Green Revolution, also known as the Third Agricultural Revolution, was a period of technology transfer initiatives that saw greatly increased crop yields and agricultural production. These changes in agriculture began in developed countrie ...
's use of conventional hybridization increased yields by breeding "
high-yielding varieties High-yielding varieties (HYVs) of agricultural crops are usually characterized by a combination of the following traits in contrast to the conventional varieties: * Higher crop yield per area (hectare) * Dwarfness * Improved response to fertilize ...
". 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 the loss of
genetic diversity Genetic diversity is the total number of genetic characteristics in the genetic makeup of a species, it ranges widely from the number of species to differences within species and can be attributed to the span of survival for a species. It is dis ...
. 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.


Different taxa


In animals


Mammals

Familiar examples of
equid hybrid Equid hybrids, also called hybrid equines, are created from the crossing of members from the horse family such as a horse, donkey and zebra.Equid Hybrids. (2014, June). Retrieved from http://www.best-top10-list.com/view/article/2811/equid-hybridsHYB ...
s are the mule, 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 bear The brown bear (''Ursus arctos'') is a large bear species found across Eurasia and North America. In North America, the populations of brown bears are called grizzly bears, while the subspecies that inhabits the Kodiak Islands of Alaska is kn ...
s are another case of a hybridizing species pairs, and
introgression Introgression, also known as introgressive hybridization, in genetics is the transfer of genetic material from one species into the gene pool of another by the repeated backcrossing of an interspecific hybrid with one of its parent species. Intro ...
among non-sister species of bears appears to have shaped the
Ursidae Bears are carnivoran mammals of the family Ursidae. They are classified as caniforms, or doglike carnivorans. Although only eight species of bears are extant, they are widespread, appearing in a wide variety of habitats throughout the Nort ...
family tree. Among many other mammal crosses are
hybrid camel A hybrid camel is a hybrid between a Bactrian camel (''Camelus bactrianus'') and dromedary (''Camelus dromedarius''). Names Hybrid camels have different names depending on zone and language. Some names include turkoman, tülu, bukht, nar, ine ...
s, crosses between a
bactrian camel The Bactrian camel (''Camelus bactrianus''), also known as the Mongolian camel or domestic Bactrian camel, is a large even-toed ungulate native to the steppes of Central Asia. It has two humps on its back, in contrast to the single-humped drome ...
and a
dromedary The dromedary (''Camelus dromedarius'' or ;), also known as the dromedary camel, Arabian camel, or one-humped camel, is a large even-toed ungulate, of the genus '' Camelus'', with one hump on its back. It is the tallest of the three species o ...
. 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 4500 years ago to ancient Syria. The first known instance of hybrid speciation in marine mammals was discovered in 2014. The
clymene dolphin The Clymene dolphin (''Stenella clymene''), in older texts known as the short-snouted spinner dolphin, is a dolphin endemic to the Atlantic Ocean. It is the only confirmed case of hybrid speciation in marine mammals, descending from the spinner ...
(''Stenella clymene'') is a hybrid of two Atlantic species, the
spinner Technology *Spinner (aeronautics), the aerodynamic cone at the hub of an aircraft propeller * Spinner (cell culture), laboratory equipment for cultivating plant or mammalian cells * Spinner (computing), a graphical widget in a GUI * Spinner (MIT Med ...
and
striped dolphin The striped dolphin (''Stenella coeruleoalba'') is an extensively studied dolphin found in temperate and tropical waters of all the world's oceans. It is a member of the oceanic dolphin family, Delphinidae. Taxonomy The striped dolphin is one o ...
s. In 2019, scientists confirmed that a skull found 30 years earlier was a hybrid between the
beluga whale The beluga whale () (''Delphinapterus leucas'') is an Arctic and sub-Arctic cetacean. It is one of two members of the family Monodontidae, along with the narwhal, and the only member of the genus ''Delphinapterus''. It is also known as the wh ...
and narwhal; dubbed the narluga.


Birds

Cagebird breeders sometimes breed bird hybrids known as mules between species of finch, such as goldfinch × canary.


Amphibians

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.


Fish

Among fish, a group of about fifty natural hybrids between
Australian blacktip shark The Australian blacktip shark (''Carcharhinus tilstoni'') is a species of requiem shark, in the family Carcharhinidae, endemic to northern and eastern Australia. Favoring the upper and middle parts of the water column, it can be found from the ...
and the larger common blacktip shark was found by Australia's eastern coast in 2012.
Russian sturgeon The Russian sturgeon (''Acipenser gueldenstaedtii''), also known as the diamond sturgeon or Danube sturgeon, is a species of fish in the family Acipenseridae. It is found in Azerbaijan, Bulgaria, Georgia, Iran, Kazakhstan, Romania, Russia, Turke ...
and
American paddlefish The American paddlefish (''Polyodon spathula,'' also known as a Mississippi paddlefish, spoon-billed cat, or spoonbill) is a species of ray-finned fish. It is the only living species of paddlefish (Polyodontidae). This family is most closely r ...
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 sturddlefish is a hybrid of the American paddlefish (''Polyodon spathula'') and the Russian sturgeon (''Acipenser gueldenstaedtii''), accidentally created by researchers in 2019 and announced in 2020. Obtaining living hybrids through breed ...
.


Cephalochordates

The two genera
Asymmetron ''Asymmetron'' is a genus of lancelets belonging to the family Branchiostomatidae Branchiostomatidae is a family of lancelets belonging to the class Leptocardii, order unknown. Genera: * '' Asymmetron'' Andrews, 1893 * ''Branchiostoma ''B ...
and
Branchiostoma ''Branchiostoma'' is one of the few living genera of lancelets ( order Amphioxiformes). It is the type genus of family Branchiostomatidae. These small vaguely eel- or snake-like animals are close relatives of vertebrates. The scientific name ...
are able to produce viable hybrid offspring, even if none have lived into adulthood so far, despite the parents' common ancestor living tens of millions of years ago.


Insects

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 The western honey bee or European honey bee (''Apis mellifera'') is the most common of the 7–12 species of honey bees worldwide. The genus name ''Apis'' is Latin for "bee", and ''mellifera'' is the Latin for "honey-bearing" or "honey carrying" ...
and an
African bee The East African lowland honey bee (''Apis mellifera scutellata'') is a subspecies of the western honey bee. It is native to central, southern and eastern Africa, though at the southern extreme it is replaced by the Cape honey bee (''Apis mellife ...
. The '' Colias eurytheme'' and '' C. philodice'' butterflies have retained enough genetic compatibility to produce viable hybrid offspring. Hybrid speciation may have produced the diverse '' Heliconius''
butterflies Butterflies are insects in the macrolepidopteran clade Rhopalocera from the order Lepidoptera, which also includes moths. Adult butterflies have large, often brightly coloured wings, and conspicuous, fluttering flight. The group comprises ...
, 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 fertilize her eggs with sperm from males of her own species, the offspring is always new queens. And when she fertilize the eggs with sperm from males of the other species, the offspring is always sterile worker ants (and because ants are
haplodiploid Haplodiploidy is a sex-determination system in which males develop from unfertilized eggs and are haploid, and females develop from fertilized eggs and are diploid. Haplodiploidy is sometimes called arrhenotoky. Haplodiploidy determines the sex ...
, 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. File:Zeedonk 800.jpg, A " zonkey", a zebra/donkey hybrid File:Jaglion.jpg, A "
jaglion A ''Panthera'' hybrid is a crossbreed between individuals of any of the five species of the genus ''Panthera'': the tiger, lion, jaguar, leopard, and snow leopard. Most hybrids would not be perpetuated in the wild as the territories of the pa ...
", a jaguar/lion hybrid File:Goldfinch Canary hybrid.JPG, A domestic canary/goldfinch hybrid


In plants

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 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'' × ''acerifolia'' 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 ''Prunus persica'' × ''Prunus americana'' is the hybrid between the peach ''Prunus persica'' (often a nectarine) and the wild American plum ''Prunus americana''. Hybrids were obtained in the 1940s at the University of Minnesota, and have been ...
'', with the female parent's name given first, or if not known, the parent's names given alphabetically. Plant species that are genetically compatible may not hybridize in nature for various reasons, including geographical isolation, differences in flowering period, or differences in pollinators. Species that are brought together by humans in gardens may hybridize naturally, or hybridization can be facilitated by human efforts, such as altered flowering period or artificial pollination. Hybrids are sometimes created by humans to produce improved plants that have some of the characteristics of each of the parent species. Much work is now being done with hybrids between crops and their wild relatives to improve disease-resistance or
climate resilience Climate resilience is defined as the "capacity of social, economic and ecosystems to cope with a hazardous event or trend or disturbance".IPCC, 2022Summary for Policymakers .-O. Pörtner, D.C. Roberts, E.S. Poloczanska, K. Mintenbeck, M. Tignor, ...
for both agricultural and horticultural crops. Some crop plants are hybrids from different genera (intergeneric hybrids), such as Triticale, × ''Triticosecale'', a wheat–
rye Rye (''Secale cereale'') is a grass grown extensively as a grain, a cover crop and a forage crop. It is a member of the wheat tribe (Triticeae) and is closely related to both wheat (''Triticum'') and barley (genus ''Hordeum''). Rye grain is u ...
hybrid. Most modern and ancient wheat breeds are themselves hybrids;
bread wheat Common wheat (''Triticum aestivum''), also known as bread wheat, is a cultivated wheat species. About 95% of wheat produced worldwide is common wheat; it is the most widely grown of all crops and the cereal with the highest monetary yield. Ta ...
, ''Triticum aestivum'', is a hexaploid hybrid of three wild grasses. Several commercial fruits including
loganberry The loganberry (''Rubus'' × ''loganobaccus'') is a hybrid of the North American blackberry (''Rubus ursinus'') and the European raspberry (''Rubus idaeus''). The plant and the fruit resemble the blackberry more than the raspberry, but the frui ...
(''Rubus'' × ''loganobaccus'') and
grapefruit The grapefruit (''Citrus'' × ''paradisi'') is a subtropical citrus tree known for its relatively large, sour to semi-sweet, somewhat bitter fruit. The interior flesh is segmented and varies in color from pale yellow to dark pink. Grapefruit ...
(''Citrus'' × ''paradisi'') are hybrids, as are garden herbs such as
peppermint Peppermint (''Mentha'' × ''piperita'') is a hybrid species of mint, a cross between watermint and spearmint. Indigenous to Europe and the Middle East, the plant is now widely spread and cultivated in many regions of the world.Euro+Med Plantb ...
(''Mentha'' × ''piperita''), and trees such as the London plane (''Platanus'' × ''acerifolia''). Among many natural plant hybrids is ''
Iris albicans ''Iris albicans'', also known as the cemetery iris, white cemetery iris, or the white flag iris, is a species of iris which was planted on graves in Muslim regions and grows in many countries throughout the Middle East and northern Africa. It was ...
'', a sterile hybrid that spreads by rhizome division, and ''
Oenothera lamarckiana ''Oenothera glazioviana'' is a species of flowering plant in the evening primrose family known by the common names large-flowered evening-primrose and redsepal evening primrose. ''Oenothera lamarckiana'' was formerly believed to be a different s ...
'', a flower that was the subject of important experiments by Hugo de Vries that produced an understanding of polyploidy. File:Trilliumhybrid2.jpg, A sterile hybrid between ''
Trillium cernuum ''Trillium cernuum'' is a species of flowering plant in the bunchflower family Melanthiaceae. The specific epithet ''cernuum'' means "drooping, curving forwards, facing downwards", a distinctive habit of its flower. It is commonly called noddi ...
'' and '' T. grandiflorum'' File:Lily Lilium 'Citronella' Flower.jpg, An ornamental lily hybrid known as ''Lilium'' 'Citronella'
Sterility in a non-polyploid hybrid is often a result of chromosome number; if parents are of differing chromosome pair number, the offspring will have an odd number of chromosomes, which leaves them unable to produce chromosomally-balanced gametes. While that is undesirable in a crop such as wheat, for which growing a crop that produces no seeds would be pointless, it is an attractive attribute in some fruits.
Triploid Polyploidy is a condition in which the cells of an organism have more than one pair of ( homologous) chromosomes. Most species whose cells have nuclei (eukaryotes) are diploid, meaning they have two sets of chromosomes, where each set contains ...
banana A banana is an elongated, edible fruit – botanically a berry – produced by several kinds of large herbaceous flowering plants in the genus ''Musa''. In some countries, bananas used for cooking may be called "plantains", distinguis ...
s and watermelons are intentionally bred because they produce no seeds and are also parthenocarpic.


In humans

There is evidence of hybridisation between modern humans and other species of the genus '' Homo''. In 2010, the Neanderthal genome project showed that 1–4% of DNA from all people living today, apart from most Sub-Saharan Africans, is of Neanderthal heritage. Analyzing the genomes of 600 Europeans and East Asians found that combining them covered 20% of the Neanderthal genome that is in the modern human population. Ancient human populations lived and interbred with Neanderthals, Denisovans, and at least one other extinct ''Homo'' species. Thus, Neanderthal and Denisovan DNA has been incorporated into human DNA by introgression. In 1998, a complete prehistorical skeleton found in Portugal, the Lapedo child, had features of both anatomically modern humans and Neanderthals. Some ancient human skulls with especially large nasal cavities and unusually shaped braincases represent human-Neanderthal hybrids. A 37,000- to 42,000-year-old human jawbone found in Romania's Oase cave contains traces of Neanderthal ancestry from only four to six generations earlier. All genes from Neanderthals in the current human population are descended from Neanderthal fathers and human mothers.


Mythology

Folk tales and myths sometimes contain mythological hybrids; the
Minotaur In Greek mythology, the Minotaur ( , ;. grc, ; in Latin as ''Minotaurus'' ) is a mythical creature portrayed during classical antiquity with the head and tail of a bull and the body of a man or, as described by Roman poet Ovid, a being "pa ...
was the offspring of a human,
Pasiphaë In ancient Greek religion and Greek mythology, Pasiphaë (; grc-gre, Πασιφάη, Pasipháē, lit=wide-shining derived from πάσι (archaic dative plural) "for all" and φάος/φῶς ''phaos/phos'' "light") was a queen of Crete, and w ...
, and a white bull. More often, they are composites of the physical attributes of two or more kinds of animals, mythical beasts, and humans, with no suggestion that they are the result of interbreeding, as in the centaur (man/horse),
chimera Chimera, Chimaera, or Chimaira (Greek for "she-goat") originally referred to: * Chimera (mythology), a fire-breathing monster of Ancient Lycia said to combine parts from multiple animals * Mount Chimaera, a fire-spewing region of Lycia or Cilicia ...
(goat/lion/snake),
hippocamp The hippocampus or hippocamp, also ''hippokampos'' (plural: hippocampi or hippocamps; grc, ἱππόκαμπος, from , "horse" and , "sea monster"
(fish/horse), and sphinx (woman/lion). The Old Testament mentions a first generation of half-human hybrid
giants A giant is a being of human appearance, sometimes of prodigious size and strength, common in folklore. Giant(s) or The Giant(s) may also refer to: Mythology and religion *Giants (Greek mythology) *Jötunn, a Germanic term often translated as 'gi ...
, the
Nephilim The Nephilim (; ''Nəfīlīm'') are mysterious beings or people in the Hebrew Bible who are large and strong. The word ''Nephilim'' is loosely translated as ''giants'' in some translations of the Hebrew Bible, but left untranslated in others. ...
, while the
apocryphal Apocrypha are works, usually written, of unknown authorship or of doubtful origin. The word ''apocryphal'' (ἀπόκρυφος) was first applied to writings which were kept secret because they were the vehicles of esoteric knowledge considered ...
Book of Enoch describes the Nephilim as the wicked sons of fallen angels and attractive women.


See also

*
Canid hybrid Canid hybrids are the result of interbreeding between the species of the genus ''Canis''. This often occurs in the wild, and in particular between domestic or feral dogs with wild native canids. Genetic considerations The wolf-like canids are a g ...
*
Chimera (genetics) A genetic chimerism or chimera ( ) is a single organism composed of cells with more than one distinct genotype. In animals, this means an individual derived from two or more zygotes, which can include possessing blood cells of different blood ty ...
*
Chloroplast capture Chloroplast capture is an evolutionary process through which inter-species hybridization and subsequent backcrosses yield a plant with new genetic combination of nuclear and chloroplast genomes. For instance, 1) species A's (having chloroplast gen ...
(botany) *
Eukaryote hybrid genome Eukaryote hybrid genomes result from interspecific hybridization, where closely related species mate and produce offspring with admixed genomes. The advent of large-scale genomic sequencing has shown that hybridization is common, and that it ma ...
* Felid hybrids * Genetic admixture * Genetic erosion *
Grex (horticulture) The term ''grex'' (plural ''greges'' or ''grexes''; abbreviation gx), derived from the Latin noun , , meaning 'flock', has been expanded in botanical nomenclature to describe hybrids of orchids, based solely on their parentage. Grex names are on ...
*
Hybridogenesis Parthenogenesis (; from the Greek grc, παρθένος, translit=parthénos, lit=virgin, label=none + grc, γένεσις, translit=génesis, lit=creation, label=none) is a natural form of asexual reproduction in which growth and development ...
*
Hybrot A hybrot (short for "hybrid robot") is a cybernetic organism in the form of a robot controlled by a computer consisting of both electronic and biological elements. The biological elements are typically rat neurons connected to a computer chip. Thi ...
*
Inbreeding Inbreeding is the production of offspring from the mating or breeding of individuals or organisms that are closely related genetically. By analogy, the term is used in human reproduction, but more commonly refers to the genetic disorders and ...
*
Breeding back Breeding back is a form of artificial selection by the deliberate selective breeding of domestic (but not exclusively) animals, in an attempt to achieve an animal breed with a phenotype that resembles a wild type ancestor, usually one that ha ...
*
Interspecific pregnancy Interspecific pregnancy (literally ''pregnancy between species'', also called interspecies pregnancy or xenopregnancy)Page 126 in: is the pregnancy involving an embryo or fetus belonging to another species than the carrier. Strictly, it excludes ...
* * * Horizontal gene transfer *
Inferring horizontal gene transfer Horizontal or lateral gene transfer (HGT or LGT) is the transmission of portions of genomic DNA between organisms through a process decoupled from vertical inheritance. In the presence of HGT events, different fragments of the genome are the resu ...
* Agrobacterium, a bacterium well known for its ability to transfer DNA between itself and plants. *
List of plant hybrids This is a list of plant hybrids created intentionally or by chance and exploited commercially in agriculture or horticulture. The hybridization Hybridization (or hybridisation) may refer to: *Hybridization (biology), the process of combining dif ...
* List of genetic hybrids *
Macropod hybrids Macropod hybrids are hybrids of animals within the family Macropodidae, which includes kangaroos and wallabies. Several macropod hybrids have been experimentally bred, including: Some hybrids between similar species have been achieved by housin ...
* Purebred * Selective breeding *
Genetic use restriction technology Genetic use restriction technology (GURT), also known as terminator technology or suicide seeds, is the name given to proposed methods for restricting the use of genetically modified crops by activating (or deactivating) some genes only in respon ...


Notes


References


External links


Artificial Hybridisation
 – Artificial Hybridisation in orchids



Evolution Revolution: Two Species Become One, Study Says (nationalgeographic.com)

nbsp;– Creation of new species through hybridization was thought to be common only in plants, and rare in animals.
What is a human admixed embryo?
{{DEFAULTSORT:Hybrid (Biology) Biology terminology Botanical nomenclature Evolutionary biology Population genetics Breeding