Interbreeding of dingoes with other domestic dogs
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In biology, 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), 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 are. Species are reproductively isolated 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 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 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 may threaten many species with extinction, while
genetic erosion Genetic erosion (also known as genetic depletion) is a process where the limited gene pool of an endangered species diminishes even more when reproductive individuals die off before reproducing with others in their endangered low population. The t ...
from monoculture 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; many commercially useful fruits, flowers, garden herbs, and trees have been produced by hybridisation. One such flower, '' Oenothera lamarckiana'', was central to early genetics research into mutationism and polyploidy. It 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 resulted in the development of distinct breeds (usually called cultivars in reference to plants); crossbreeds between them (without any wild
stock In finance, stock (also capital stock) consists of all the shares by which ownership of a corporation or company is divided.Longman Business English Dictionary: "stock - ''especially AmE'' one of the shares into which ownership of a company ...
) 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 Extinction, extinct species or subspecies of archaic humans who lived in Eurasia until about 40,000 years ag ...
and anatomically modern humans are thought to have interbred as recently as 40,000 years ago.
Mythological hybrid Hybrid beasts are creatures composed of parts from different animals, including humans, appearing in the folklore of a variety of cultures as legendary creatures. In burial sites Remains similar to those of mythological hybrids have been found ...
s 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
centaur A centaur ( ; grc, κένταυρος, kéntauros; ), or occasionally hippocentaur, is a creature from Greek mythology with the upper body of a human and the lower body and legs of a horse. Centaurs are thought of in many Greek myths as being ...
s 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 Ort ...
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. Single cross hybrids result from the cross between two
true-breeding organism A true-breeding organism, sometimes also called a purebred ''(biology slang: pure line'' or ''true-breeding line)'', is an organism that always passes down certain phenotypic traits (i.e. physically expressed traits) to its offspring of many genera ...
s 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 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 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 ...
that, if grown and bred in a small monoculture free of external
pollen Pollen is a powdery substance produced by seed plants. It consists of pollen grains (highly reduced microgametophytes), which produce male gametes (sperm cells). Pollen grains have a hard coat made of sporopollenin that protects the gametophyt ...
(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 zones 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 wi ...
'' 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 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 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'', 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 In biological classification, subspecies is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (morphology), but that can successfully interbreed. Not all species ...
(such as between the Dog 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 obse ...
; 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 Sea urchins () are spiny, globular echinoderms in the class Echinoidea. About 950 species of sea urchin live on the seabed of every ocean and inhabit every depth zone from the intertidal seashore down to . The spherical, hard shells (tests) of ...
'' Strongylocentrotus purpuratus'' (female) and the sand dollar ''
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 Sterile or sterility may refer to: *Asepsis, a state of being free from biological contaminants * Sterile (archaeology), a sediment deposit which contains no evidence of human activity *Sterilization (microbiology), any process that eliminates or ...
, preventing gene flow between the species. Sterility is often attributed to the different number of chromosomes between the two species. For example,
donkey The domestic donkey is a hoofed mammal in the family Equidae, the same family as the horse. It derives from the African wild ass, ''Equus africanus'', and may be classified either as a subspecies thereof, ''Equus africanus asinus'', or as a ...
s have 62 chromosomes, horses have 64 chromosomes, and
mule The mule is a domestic equine hybrid between a donkey and a horse. It is the offspring of a male donkey (a jack) and a female horse (a mare). The horse and the donkey are different species, with different numbers of chromosomes; of the two pos ...
s or
hinnies A hinny is a domestic equine hybrid, the offspring of a male horse (a stallion) and a female donkey (a jenny). It is the reciprocal cross to the more common mule, which is the product of a male donkey (a jack) and a female horse (a mare). The h ...
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 last ...
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''; : wolves), also known as the gray wolf or grey wolf, is a large canine native to Eurasia and North America. More than thirty subspecies of ''Canis lupus'' have been recognized, and gray wolves, as popularly ...
and the
coyote The coyote (''Canis latrans'') is a species of canis, 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 ecologica ...
, although its taxonomic status has been a subject of controversy. The European
edible frog The edible frog (''Pelophylax'' kl. ''esculentus'') is a species of common European frog, also known as the common water frog or green frog (however, this latter term is also used for the North American species ''Rana clamitans''). It is used ...
is a semi-permanent hybrid between
pool frog The pool frog (''Pelophylax lessonae'') is a European frog in the family Ranidae. Its specific name was chosen by the Italian herpetologist Lorenzo Camerano in 1882, in order to honour his master Michele Lessona. Description The pool frog is ...
s and
marsh frog The marsh frog (''Pelophylax ridibundus'') is a species of water frog native to Europe and parts of western Asia. Description The marsh frog is the largest type of frog in most of its range, with males growing to a size around 100 mm (3.9 ...
s; 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 Holocen ...
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 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 Ploidy () is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes. Sets of chromosomes refer to the number of maternal and paternal chromosome copies, respectively ...
), 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 Hybrid may refer to: Science * Hybrid (biology), an offspring resulting from cross-breeding ** Hybrid grape, grape varieties produced by cross-breeding two ''Vitis'' species ** Hybridity, the property of a hybrid plant which is a union of two dif ...
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 a bear shot by a hunter in the North West Territories confirmed the existence of naturally-occurring and fertile
grizzly–polar bear hybrid A grizzly–polar bear hybrid (also named grolar bear, pizzly bear, zebra bear, grizzlar, or nanulak) is a rare ursid hybrid that has occurred both in captivity and in the wild. In 2006, the occurrence of this hybrid in nature was confirmed by t ...
s.


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 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") 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 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 processes ...
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 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.


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 swarm A hybrid swarm is a population of hybrids that has survived beyond the initial hybrid generation, with interbreeding between hybrid individuals and backcrossing with its parent types. Such population are highly variable, with the genetic and phe ...
s (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 In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...
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 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 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, starti ...
, the Green Revolution'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 bear The polar bear (''Ursus maritimus'') is a hypercarnivorous bear whose native range lies largely within the Arctic Circle, encompassing the Arctic Ocean, its surrounding seas and surrounding land masses. It is the largest extant bear specie ...
s and brown bears 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. Intr ...
among non-sister species of bears appears to have shaped the Ursidae family tree. Among many other mammal crosses are hybrid camels, crosses between 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 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 and striped dolphins. In 2019, scientists confirmed that a skull found 30 years earlier was a hybrid between the beluga whale and
narwhal The narwhal, also known as a narwhale (''Monodon monoceros''), is a medium-sized toothed whale that possesses a large "tusk" from a protruding canine tooth. It lives year-round in the Arctic waters around Greenland, Canada and Russia. It is o ...
; dubbed the narluga.


Birds

Cagebird breeders sometimes breed bird hybrids known as
mules A mule is the offspring of a female horse and a male donkey. Mule, Mules, MULE or The Mule can also refer to: Animals * Mule (sheep), in British sheep farming, a cross between a meat ram and a hardy mountain ewe * Mule deer (''Odocoileus hemio ...
between species of finch, such as
goldfinch Goldfinch or The Goldfinch may refer to: Birds * European goldfinch, ''Carduelis carduelis'' * Some species of the genus '' Spinus'': ** American goldfinch, ''Spinus tristis'' ** Lawrence's goldfinch, ''Spinus lawrencei'' ** Lesser goldfinc ...
×
canary Canary originally referred to the island of Gran Canaria on the west coast of Africa, and the group of surrounding islands (the Canary Islands). It may also refer to: Animals Birds * Canaries, birds in the genera ''Serinus'' and ''Crithagra'' i ...
.


Amphibians

Among amphibians, Japanese
giant salamander The Cryptobranchidae are a family of fully aquatic salamanders commonly known as the giant salamanders. They include the largest living amphibians. The family is native to China, Japan, and the eastern United States. They constitute one of two li ...
s 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 i ...
and the larger common blacktip shark was found by Australia's eastern coast in 2012. Russian sturgeon 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 breeding ...
.


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'' Costa, ...
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 and an African bee. The ''
Colias eurytheme ''Colias eurytheme'', the orange sulphur, also known as the alfalfa butterfly and in its larval stage as the alfalfa caterpillar, is a butterfly of the family Pieridae, where it belongs to the lowland group of " clouded yellows and sulphurs" sub ...
'' 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 (biology), order Lepidoptera, which also includes moths. Adult butterflies have large, often brightly coloured wings, and conspicuous, fluttering flight. The ...
, 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, 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 par ...
", 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
pollinator A pollinator is an animal that moves pollen from the male anther of a flower to the female stigma of a flower. This helps to bring about fertilization of the ovules in the flower by the male gametes from the pollen grains. Insects are the maj ...
s. 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 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 (''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 is ...
(''Citrus'' × ''paradisi'') are hybrids, as are garden herbs such as peppermint (''Mentha'' × ''piperita''), and trees such as the
London plane London is the capital and largest city of England and the United Kingdom, with a population of just under 9 million. It stands on the River Thames in south-east England at the head of a estuary down to the North Sea, and has been a major se ...
(''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'', 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
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 African Sub-Saharan Africa is, geographically, the area and regions of the continent of Africa that lies south of the Sahara. These include West Africa, East Africa, Central Africa, and Southern Africa. Geopolitically, in addition to the African ...
s, 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 The Denisovans or Denisova hominins ) are an extinct species or subspecies of archaic human that ranged across Asia during the Lower and Middle Paleolithic. Denisovans are known from few physical remains and consequently, most of what is known ...
, 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 Lagar Velho 1, also known as the Lagar Velho boy or Lapedo child, is a complete prehistorical skeleton found in Portugal, believed to be a hybrid that had a Neanderthal parent and an anatomically modern human parent. In 1998, this discovery of an ...
, 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, 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 A centaur ( ; grc, κένταυρος, kéntauros; ), or occasionally hippocentaur, is a creature from Greek mythology with the upper body of a human and the lower body and legs of a horse. Centaurs are thought of in many Greek myths as being ...
(man/horse), chimera (goat/lion/snake), hippocamp (fish/horse), and sphinx (woman/lion). The
Old Testament The Old Testament (often abbreviated OT) is the first division of the Christian biblical canon, which is based primarily upon the 24 books of the Hebrew Bible or Tanakh, a collection of ancient religious Hebrew writings by the Israelites. The ...
mentions a first generation of half-human hybrid giants, 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 *
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 ...
*
Chloroplast capture Chloroplast capture is an evolutionary process through which inter-species Hybrid (biology), hybridization and subsequent backcrossing, backcrosses yield a plant with new genetic combination of nuclear and chloroplast genomes. For instance, 1) speci ...
(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 may ...
* Felid hybrids * Genetic admixture *
Genetic erosion Genetic erosion (also known as genetic depletion) is a process where the limited gene pool of an endangered species diminishes even more when reproductive individuals die off before reproducing with others in their endangered low population. The t ...
* Grex (horticulture) *
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 * Inbreeding *
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 has g ...
*
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 ''Agrobacterium'' is a genus of Gram-negative bacteria established by H. J. Conn that uses horizontal gene transfer to cause tumors in plants. ''Agrobacterium tumefaciens'' is the most commonly studied species in this genus. ''Agrobacterium'' is ...
, a bacterium well known for its ability to transfer DNA between itself and plants. * List of plant hybrids * 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 respo ...


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