interspecific hybrids
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In
biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanisms, Development ...

biology
, a hybrid is the offspring resulting from combining the qualities of two organisms of different breeds, varieties, species or genera through
sexual reproduction Sexual reproduction is a type of reproduction Reproduction (or procreation or breeding) is the biological process Biological processes are those processes that are vital for an organism In biology, an organism (from Ancient Greek, ...
. Hybrids are not always intermediates between their parents (such as in
blending inheritance Blending inheritance is an Superseded scientific theories, obsolete theory in biology from the 19th century. The theory is that the progeny inheritance (biology), inherits any characteristic as the average of the parents' values of that characteris ...

blending inheritance
), but can show
hybrid vigor Heterosis, hybrid vigor, or outbreeding enhancement is the improved or increased function of any biological quality in a Hybrid (biology), hybrid offspring. An offspring is heterotic if its trait (biology), traits are enhanced as a result of mi ...

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 Genetics is a branch of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, p ...

genetics
, attention is focused on the numbers of
chromosome A chromosome is a long DNA Deoxyribonucleic acid (; DNA) is a molecule File:Pentacene on Ni(111) STM.jpg, A scanning tunneling microscopy image of pentacene molecules, which consist of linear chains of five carbon rings. A mole ...

chromosome
s. In taxonomy, a key question is how closely related the parent
species In biology, a species is the basic unit of biological classification, 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 individu ...

species
are. Species are
reproductively isolated The mechanisms of reproductive isolation are a collection of evolutionary mechanisms, ethology, behaviors and physiology, physiological processes critical for speciation. They prevent members of different species from producing offspring, or ensur ...
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 American and British English spelling differences#-ise.2C -ize .28-isation.2C -ization.29, spelling differences), also known as generative fertilisation, syngamy and impregnation, is the fusion of gametes ...

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 Hybrid speciation is a form of speciation where Hybrid (biology), hybridization between two different species leads to a new species, reproductively isolated from the parent species. Previously, reproductive isolation between two species and their ...
, including important crop plants such as
wheat Wheat is a grass widely cultivated for its seed, a cereal grain which is a worldwide staple food. The many species of wheat together make up the genus ''Triticum''; the most widely grown is common wheat (''T. aestivum''). The archaeological r ...

wheat
, where the number of chromosomes has been doubled.
Human impact on the environment Human impact on the environment or anthropogenic impact on the environment includes changes to and to s, , and caused directly or indirectly by humans, including , (such as ), and , , and . Modifying the environment to fit the needs of i ...
has resulted in an increase in the interbreeding between regional species, and the proliferation of
introduced species (''Melilotus sp.''), introduced and Naturalisation (biology), naturalized in the Americas from Europe as a forage and cover crop An introduced species, alien species, exotic species, adventive species, immigrant species, foreign species, non-in ...
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 has ...
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 ...
from
monoculture In agriculture Agriculture is the science, art and practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentism, sedentary human civilization, whereby farming of domestication, domesticated spe ...
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 Horticulture is the art of cultivating plants in gardens to produce food and medicinal ingredients, or for comfort and ornamental purposes. Horticulturists are agriculturists who grow flowers, fruits and nuts, vegetables and herbs, as well as orn ...
and modern
agriculture Agriculture is the science, art and practice of cultivating plants and livestock. Agriculture was the key development in the rise of , whereby farming of species created food that enabled people to live in cities. The began thousands of ...

agriculture
; 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 sp ...
'', 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 Charles Robert Darwin (; 12 February 1809 – 19 April 1882) was an English natur ...
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 fertile Fertility is the quality of being able to produce children. As a measure, the fertility rate is the average number of children that a woman has in her lifetime and is quantified demographically. Fertility is most ...

beefalo
and
wolfdog A wolfdog is a canine Canine may refer to: Zoology * dog-like mammals (i.e. members of the canid subfamily Caninae) ** ''Canis'', a genus including dogs, wolves, coyotes, and jackals ** Dog, the domestic dog * Canine tooth, in mammalian oral ...

wolfdog
s. Human
selective breeding Selective breeding (also called artificial selection) is the process by which humans use animal breeding Animal breeding is a branch of animal science Animal science (also bioscience) is described as "studying the biology Biology i ...
of
domesticated animals This page gives a list of domestic 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 includes s ...
and
plants Plants are predominantly photosynthetic Photosynthesis is a process used by plants and other organisms to Energy transformation, convert light energy into chemical energy that, through cellular respiration, can later be released to fuel t ...
has resulted in the development of distinct
breeds A breed is a specific group of domestic animals having homogeneous Homogeneity and heterogeneity are concepts often used in the Science, sciences and statistics relating to the Uniformity (chemistry), uniformity of a Chemical substance, substan ...
(usually called cultivars in reference to plants);
crossbreed A crossbreed is an organism with purebred Purebreds, also called purebreeds, are "cultivated varieties" (''cultivars'') of an animal species achieved through the process of selective breeding. When the pedigree chart, lineage of a purebred anim ...

crossbreed
s between them (without any wild
stock In finance, stock (also capital stock) consists of all of the shares In financial markets A financial market is a market in which people trade financial securities and derivatives at low transaction costs. Some of the securities in ...
) are sometimes also imprecisely referred to as "hybrids". Hybrid humans existed in prehistory. For example,
Neanderthals Neanderthals (, also Neandertals, ''Homo neanderthalensis'' or ''Homo sapiens neanderthalensis'') are an extinct species In biology Biology is the natural science that studies life and living organisms, including their anatomy, phys ...
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 animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotrop ...
s appear in human culture in forms as diverse as the
Minotaur In Greek mythology Greek mythology is the body of myths originally told by the Ancient Greece, ancient Greeks, and a genre of Ancient Greek folklore. These stories concern the Cosmogony, origin and Cosmology#Metaphysical cosmology, nature ...

Minotaur
, 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 a ...

centaur
s and
sphinx A sphinx ( , grc, σφίγξ , Aeolic Greek, Boeotian: , plural sphinxes or sphinges) is a mythical creature with the head of a human and the body of a lion with the wings of a falcon. In Culture of Greece, Greek tradition, the sphinx has the ...

sphinx
es, and the
Nephilim The Nephilim (; ) are mysterious beings or people mentioned in the Hebrew Bible. They are large and strong; the word ''Nephilim'' is loosely translated as '' giants'' in some Bibles but left untranslated in others. Some traditional Jewish expl ...
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 400 AD. Some Christian churches include ...
described as the wicked sons of
fallen angel In , fallen angels are s who were expelled from heaven. The literal term "fallen angel" appears neither in the nor in other scriptures, but is used to describe angels cast out of heaven"Mehdi Azaiez, , Tommaso Tesei, Hamza M. Zafer ''The Q ...

fallen angel
s 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 word A portmanteau (, ) or portmanteau word (from "portmanteau (luggage)") is a Blend word, blend of words
s, starting in the 1920s with the breeding of tiger–lion hybrids (
liger The liger is a hybrid offspring of a male lion The lion (''Panthera leo'') is a species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of b ...

liger
and
tigon A tigon () or tiglon () is the hybrid offspring of a male tiger The tiger (''Panthera tigris'') is the largest extant taxon, living Felidae, cat species and a member of the genus ''Panthera''. It is most recognisable for its dark vertic ...

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 Homogeneity and heterogeneity are concepts often used in the Science, sciences and statistics relating to the Uniformity (chemistry), uniformity of a Chemical substance, substan ...
. Single cross hybrids result from the cross between two
true-breeding organism A true-breeding organism, sometimes also called a purebred, is an organism that always passes down certain phenotypic right , Here the relation between genotype and phenotype is illustrated, using a Punnett square, for the character of petal ...
s which produces an
F1 hybrid An F1 hybrid (also known as filial 1 hybrid) is the first filial generation A generation is "all of the people born and living at about the same time, regarded collectively." It can also be described as, "the average period, generally conside ...
(first filial generation). The cross between two different
homozygous Zygosity (the noun, zygote A zygote (from Greek ζυγωτός ''zygōtos'' "joined" or "yoked", from ζυγοῦν ''zygoun'' "to join" or "to yoke") is a eukaryotic cell formed by a fertilization event between two gamete A gamete ( /ˈ ...
lines produces an F1 hybrid that is
heterozygous Zygosity (the noun, zygote, is from the Greek zygotos "yoked," from zygon "yoke") () is the degree to which both copies of a chromosome or gene have the same genetic sequence. In other words, it is the degree of similarity of the alleles in an org ...

heterozygous
; having two alleles, one contributed by each parent and typically one is
dominant Domination or dominant may refer to: Society * World domination, which is mainly a conspiracy theory * Colonialism in which one group (usually a nation) invades another region for material gain or to eliminate competition * Chauvinism in which a p ...
and the other
recessive In genetics Genetics is a branch of biology concerned with the study of genes, genetic variation, and heredity in organisms.Hartl D, Jones E (2005) Though heredity had been observed for millennia, Gregor Mendel, Moravia, Moravian scientist ...
. Typically, the F1 generation is also
phenotypically
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 Population typically refers the number of people in a single area whether it be a city or town, region, country, or the world. Governments typically quantify the size of the resident population within their jurisdiction by a process called a ...

population
with those of another population. These include interspecific hybrids or crosses between different breeds. In
horticulture Horticulture is the art of cultivating plants in gardens to produce food and medicinal ingredients, or for comfort and ornamental purposes. Horticulturists are agriculturists who grow flowers, fruits and nuts, vegetables and herbs, as well as orn ...
, the term stable hybrid is used to describe an
annual plant Image:Doperwt rijserwt peulen Pisum sativum.jpg, 240px, Peas are an annual plant. An annual plant is a plant that completes its biological life cycle, life cycle, from germination to the production of seeds, within one growing season, and then dies ...
that, if grown and bred in a small
monoculture In agriculture Agriculture is the science, art and practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentism, sedentary human civilization, whereby farming of domestication, domesticated spe ...
free of external
pollen Pollen Tube Diagram Pollen is a powdery substance consisting of pollen grains which are microsporophytes of seed plants The spermatophytes, also known as phanerogams (taxon Phanerogamae) or phaenogams (taxon Phaenogamae), comprise those plan ...

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 zoneA hybrid zone exists where the ranges of two interbreeding species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often ...
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 Butterflies are insect Insects or Insecta (from Latin Latin (, or , ) is a classical language belonging to the Italic languages, Itali ...

Limenitis arthemis
'' has two major subspecies in North America, ''L. a. arthemis'' (the white admiral) and ''L. a. astyanax'' (the red-spotted purple). The white admiral has a bright, white band on its wings, while the red-spotted purple has cooler blue-green shades. 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 one of two, or more, forms of a given gene In biology, a gene (from ''genos'' "...Wilhelm Johannsen coined the word gene to describe the Mendelian_inheritance ...
s of the same
gene In biology, a gene (from ''genos'' "...Wilhelm Johannsen coined the word gene to describe the Mendelian_inheritance#History, Mendelian units of heredity..." (Greek language, Greek) meaning ''generation'' or ''birth'' ) is a basic unit of her ...

gene
, where for instance one allele may code for a lighter coat colour than the other. A structural hybrid results from the fusion of
gamete A gamete ( /ˈɡæmiːt/; from Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the foll ...
s 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 or variants an individual carries in a particular gene or genetic location. The number of alleles an individual can have in a specific ...
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 sp ...
'', because all homozygous combinations are lethal. In the early history of genetics,
Hugo de Vries Hugo Marie de Vries () (16 February 1848 – 21 May 1935) was a Dutch botanist Botany, also called , plant biology or phytology, is the science Science (from the Latin word ''scientia'', meaning "knowledge") is a systematic enterpris ...

Hugo de Vries
supposed these were caused by mutation.


Taxonomy

From the point of view of
taxonomy Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The term may also refer to a specific classification scheme. Originally used only about biological ...
, hybrids differ according to their parentage. Hybrids between different
subspecies In biological classification In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactio ...
(such as between the
Dog The dog or domestic dog (''Canis familiaris'' or ''Canis lupus familiaris'') is a Domestication, domesticated descendant of the wolf which is characterized by an upturning tail. The dog Origin of the domestic dog, derived from an Pleistocene ...

Dog
and
Eurasian wolf The Eurasian wolf (''Canis lupus lupus''), also known as the common wolfMech, L. David (1981), ''The Wolf: The Ecology and Behaviour of an Endangered Species'', University of Minnesota Press, p. 354, or Middle Russian forest wolf,Heptner, V. G. & ...
) are called intra-specific hybrids. Interspecific hybrids are the offspring from interspecies mating; these sometimes result in hybrid speciation. Intergeneric hybrids result from matings between different genera, such as between
sheep Sheep (''Ovis aries'') are quadruped The zebra is a quadruped. Quadrupedalism is a form of terrestrial locomotion where a tetrapod Tetrapods (; from Greek 'four' and 'foot') are four-limbed animals constituting the superclass Tetrapo ...
and
goat The domestic goat or simply goat (''Capra hircus'') is a domesticated species of goat-antelope The subfamily Caprinae is part of the ruminant Ruminants are herbivorous mammals of the suborder Ruminantia that are able to acquire nutrient ...

goat
s. 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 made with the sea urchin ''Strongylocentrotus purpuratus'' (female) and the sand dollar ''Dendraster excentricus'' (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 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 Sterility (physiology), 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, horses have 64 chromosomes, and mules or hinny, 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 is a natural hybrid. The American red wolf appears to be a hybrid of the gray wolf and the coyote, although its taxonomic status has been a subject of controversy. The European edible frog is a semi-permanent hybrid between pool frogs and marsh frogs; its population requires the continued presence of at least one of the parent species. Cave paintings indicate that the European bison is a natural hybrid of the aurochs and the steppe bison. Plant hybridization is more commonplace compared to animal hybridization. Many crop species are hybrids, including notably the polyploid
wheat Wheat is a grass widely cultivated for its seed, a cereal grain which is a worldwide staple food. The many species of wheat together make up the genus ''Triticum''; the most widely grown is common wheat (''T. aestivum''). The archaeological r ...

wheat
s: 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 Eukaryote hybrid genome, hybrid genome can remain stable. Many
hybrid zoneA hybrid zone exists where the ranges of two interbreeding species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often ...
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 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, heterosis, hybrid vigour, or heterozygote advantage. This is most common with plant hybrids. A Transgressive segregation, transgressive phenotype is a phenotype that displays more extreme characteristics than either of the parent lines. Plant breeding, 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''). 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 and species introductions. Such impacts make it difficult to conservation genetics, conserve the genetics of populations undergoing introgression, 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 swarms (highly variable populations with much interbreeding as well as backcrossing with the parent species). Depending on where a population falls along this continuum, the management plans for that population will change. Hybridization is currently an area of great discussion within wildlife management and habitat management. Global warming, 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 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 Fitness (biology), 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, the Green Revolution's use of conventional hybridization increased yields by breeding "high-yielding varieties". The replacement of locally indigenous breeds, compounded with unintentional cross-pollination and crossbreeding (genetic mixing), has reduced the gene pools of various wild and indigenous breeds resulting in the loss of genetic diversity. Since the indigenous breeds are often well-adapted to local extremes in climate and have immunity to local pathogens, this can be a significant genetic erosion of the gene pool for future breeding. Therefore, commercial plant geneticists strive to breed "widely adapted" cultivars to counteract this tendency.


In different taxa


In animals


Mammals

Familiar examples of equid hybrids 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 bears are another case of a hybridizing species pairs, and introgression among non-sister species of bears appears to have shaped the Ursidae family tree. Among many other mammal crosses are hybrid camels, crosses between a bactrian camel and a dromedary camel, dromedary. There are many examples of Felid hybrid, felid hybrids, including the liger. The first known instance of hybrid speciation in marine mammals was discovered in 2014. The clymene dolphin (''Stenella clymene'') is a hybrid of two Atlantic species, the spinner dolphin, spinner and striped dolphins. In 2019, scientists confirmed that a skull found 30 years earlier was a hybrid between the beluga whale and narwhal; dubbed the narluga.


Birds

Cagebird breeders sometimes breed bird hybrids known as Mule (bird), mules between species of finch, such as Carduelis, goldfinch × Domestic canary, 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 and the larger Blacktip shark, common blacktip shark was found by Australia's eastern coast in 2012. Russian sturgeon and American paddlefish were hybridized in captivity when sperm from the paddlefish and eggs from the sturgeon were combined, unexpectedly resulting in viable offspring. This hybrid is called a sturddlefish.


Invertebrates

Among insects, so-called Africanized bee, killer bees were accidentally created during an attempt to breed a strain of bees that would both produce more honey and be better adapted to tropical conditions. It was done by crossing a European honey bee and an African bee. The ''Colias eurytheme'' and ''Colias philodice, C. philodice'' butterflies have retained enough genetic compatibility to produce viable hybrid offspring. Hybrid speciation may have produced the diverse ''Heliconius'' butterfly, butterflies, but that is disputed. File:Zeedonk 800.jpg, A "Zebroid, zonkey", a zebra/donkey hybrid File:Jaglion.jpg, A "jaglion", a jaguar/lion hybrid File:Goldfinch Canary hybrid.JPG, A mule (bird), 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. Hybrid name, Plant hybrids are generally given names that include an "×" (not in italics), such as Platanus × acerifolia, ''Platanus'' × ''acerifolia'' for the London plane, a natural hybrid of ''Platanus orientalis, P. orientalis'' (oriental plane) and ''Platanus occidentalis, P. occidentalis'' (American sycamore). The parent's names may be kept in their entirety, as seen in ''Prunus persica × Prunus americana'', 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 for both agricultural and horticultural crops. Some list of plant hybrids, crop plants are hybrids from different genera (intergeneric hybrids), such as Triticale, × ''Triticosecale'', a wheat–rye hybrid. Most modern and ancient wheat breeds are themselves hybrids; bread wheat, ''Triticum aestivum'', is a hexaploid hybrid of three wild grasses. Several commercial fruits including loganberry (''Rubus'' × ''loganobaccus'') and grapefruit (''Citrus'' × ''paradisi'') are hybrids, as are garden herbs such as peppermint (''Mentha'' × ''piperita''), and trees such as the London plane (''Platanus'' × ''acerifolia''). Among many natural plant hybrids is ''Iris albicans'', 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 sp ...
'', a flower that was the subject of important experiments by
Hugo de Vries Hugo Marie de Vries () (16 February 1848 – 21 May 1935) was a Dutch botanist Botany, also called , plant biology or phytology, is the science Science (from the Latin word ''scientia'', meaning "knowledge") is a systematic enterpris ...

Hugo de Vries
that produced an understanding of polyploidy. File:Trilliumhybrid2.jpg, A sterile hybrid between ''Trillium cernuum'' and ''Trillium grandiflorum, 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 bananas and watermelons are intentionally bred because they produce no seeds and are also parthenocarpy, 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 archaic human, 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 Oase 2, 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. A Neanderthal skull unearthed in Italy in 1957 reveals Neanderthal mitochondrial DNA, which is passed on through only the maternal lineage, but the skull has a chin shape similar to modern humans. It is proposed that it was the offspring of a Neanderthal mother and a human father.


In mythology

Folk tales and myths sometimes contain mythological hybrids; the
Minotaur In Greek mythology Greek mythology is the body of myths originally told by the Ancient Greece, ancient Greeks, and a genre of Ancient Greek folklore. These stories concern the Cosmogony, origin and Cosmology#Metaphysical cosmology, nature ...

Minotaur
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 a ...

centaur
(man/horse), Chimera (mythology), chimera (goat/lion/snake), hippocamp (fish/horse), and
sphinx A sphinx ( , grc, σφίγξ , Aeolic Greek, Boeotian: , plural sphinxes or sphinges) is a mythical creature with the head of a human and the body of a lion with the wings of a falcon. In Culture of Greece, Greek tradition, the sphinx has the ...

sphinx
(woman/lion). The Old Testament mentions a first generation of half-human hybrid giant (mythology), giants, the
Nephilim The Nephilim (; ) are mysterious beings or people mentioned in the Hebrew Bible. They are large and strong; the word ''Nephilim'' is loosely translated as '' giants'' in some Bibles but left untranslated in others. Some traditional Jewish expl ...
, while the Biblical apocrypha, apocryphal Book of Enoch describes the Nephilim as the wicked sons of
fallen angel In , fallen angels are s who were expelled from heaven. The literal term "fallen angel" appears neither in the nor in other scriptures, but is used to describe angels cast out of heaven"Mehdi Azaiez, , Tommaso Tesei, Hamza M. Zafer ''The Q ...

fallen angel
s and attractive women.


See also

* Canid hybrid * Chimera (genetics) * Chloroplast capture (botany) * Eukaryote hybrid genome * Felid hybrids * Genetic admixture * Genetic erosion * Grex (horticulture) * Hybridogenesis * Hybrot * Inbreeding * Breeding back * Interspecific pregnancy * * Horizontal gene transfer * Inferring horizontal gene transfer * Agrobacterium, a bacterium well known for its ability to transfer DNA between itself and plants. * List of plant hybrids * List of genetic hybrids * Macropod hybrids * Purebred * Selective breeding * Genetic use restriction technology


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) Hybridisation (biology), Hybrid organisms, Biology terminology Botanical nomenclature Evolutionary biology Population genetics Breeding