Hybrid (biology)

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For other uses, see Hybrid.
Hercules, a "liger", a lion/tiger hybrid.

In biology a hybrid, also known as cross breed, is the result of mixing, through sexual reproduction, two animals or plants of different breeds, varieties, species or genera.[1] Using genetic terminology, it may be defined as follows.[2]


From a taxonomic perspective, hybrid refers to:

  1. Offspring resulting from the interbreeding between two animal species or plant species.[3] See also hybrid speciation.
  3. The third type of hybrid consists of crosses between populations, breeds or cultivars within a single species. This meaning is often used in plant and animal breeding, where hybrids are commonly produced and selected, because they have desirable characteristics not found or inconsistently present in the parent individuals or populations.


The term hybrid is derived from Latin hybrida, meaning the "offspring of a tame sow and a wild boar", "child of a freeman and slave", etc.[5] 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.[6]

There is a popular convention of naming hybrids by forming portmanteau words. The template for this is the naming of tiger-lion hybrids as liger and tigon in the 1920s.[7] This was playfully (but unsystematically) extended to a number of other hybrids, or hypothetical hybrids, such as beefalo (1960s), humanzee (1980s), cama (1998).

Types of hybrids[edit]

Depending on the parents, there are a number of different types of hybrids;[8]

  • Double cross hybrids — result from the cross between two different F1 hybrids.[9]
  • Population hybrids — result from the crossing of plants or animals in a population with another population. These include crosses between organisms such as interspecific hybrids or crosses between different breeds.
  • Hybrid species – results from hybrid populations evolving reproductive barriers against their parent species through hybrid speciation.[12]

Interspecific hybrids[edit]




Hybrid species[edit]

Main article: Hybrid speciation

While not very common, a few animal species have been recognized as being the result of hybridization. The Lonicera fly is an example of a novel animal species that resulted from natural hybridization. The American red wolf appears to be a hybrid species between gray wolf and coyote,[15] although its taxonomic status has been a subject of controversy.[16][17][18] The European edible frog appears to be a species, but is actually a semi-permanent hybrid between pool frogs and marsh frogs. The edible frog population is dependent on the presence of at least one of the parents species to be maintained.[19] Evidence found in cave paintings indicates that the European bison is a descendant of the "Higg's bison", a natural hybrid between aurochs and steppe bison.[20][21]

Hybrid species of plants are much more common than animals. Many of the crop species are hybrids, and hybridization appears to be an important factor in speciation in some plant groups.

Examples of hybrid animals and animal populations derived from hybrids[edit]


A "zonkey", a zebra/donkey hybrid.
A "jaglion", a jaguar/lion hybrid.


See also: Bird hybrid
A mule, a domestic canary/goldfinch hybrid.


  • Hybrid iguana, a single‐cross hybrid resulting from natural interbreeding between male marine iguanas and female land iguanas since the late 2000s.


  • Japanese giant salamanders and Chinese giant salamanders have created hybrids that threaten the survival of Japanese giant salamanders due to the competition for similar resources in Japan.[24]



Hybrid plants[edit]

A sterile hybrid between Trillium cernuum and T. grandiflorum
An ornamental lily hybrid known as Lilium 'Citronella'[27]







Main article: heterosis

Hybrids are sometimes stronger than either parent variety, a phenomenon most common with plant hybrids, which when present is known as hybrid vigor (heterosis) or heterozygote advantage.[30] A transgressive phenotype is a phenotype displaying more extreme characteristics than either of the parent lines.[31] Plant breeders make use of a number of 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.[32]

Examples of plant hybrids[edit]


Interspecific plant hybrids include:

Some natural hybrids:

Hybrids in nature[edit]

Hybridization between two closely related species is actually a common occurrence in nature but is also being greatly influenced by anthropogenic changes as well.[33] Hybridization is a naturally occurring genetic process where individuals from two genetically distinct populations mate.[34] As stated above, it can occur both intraspecifically, between different distinct populations within the same species, and interspecifically, between two different species. Hybrids can be either sterile/not viable or viable/fertile. This affects the kind of effect that this hybrid will have on its and other populations that it interacts with.[35] 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 (Hybrid 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.[36]

Anthropogenic hybridization[edit]

Changes to the environment caused by humans, such as fragmentation and Introduced species, are becoming more widespread.[37] This increases the challenges in managing certain populations that are experiencing introgression, and is a focus of conservation genetics.

Introduced species and habitat fragmentation[edit]

Humans have introduced species worldwide to environments for a long time, both intentionally such as establishing a population to be used as a biological control, and unintentionally such as accidental escapes of individuals out of agriculture. This causes drastic global effects on various populations, including through hybridization.[35][38]


The hybridization continuum[edit]

There is a kind of continuum with three semi-distinct categories dealing with anthropogenic hybridization: hybridization without Introgression, hybridization with widespread introgression, and essentially a Hybrid swarm.[33] Depending on where a population falls along this continuum, the management plans for that population will change. Hybridization is currently an area of great discussion within Wildlife management and habitat management. Global climate change is creating other changes such as difference in population distributions which are indirect causes for an increase in anthropogenic hybridization.



Management of hybrids[edit]


Expression of parental traits in hybrids[edit]

When two distinct types of organisms breed with each other, the resulting hybrids typically have intermediate traits (e.g., one parent has red flowers, the other has white, and the hybrid, pink flowers).[39] 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).[39]

In a hybrid, any trait that falls outside the range of parental variation is termed heterotic. Heterotic hybrids do have new traits, that is, they are not intermediate. Positive heterosis produces more robust hybrids, they might be stronger or bigger; while the term negative heterosis refers to weaker or smaller hybrids.[40] 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 a tigon (lioness × tiger) is smaller. Also 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).[41] Spurs are absent in hybrids of the former type, although present in both parents.[42]

Genetic mixing and extinction[edit]

Main article: Genetic pollution


Effect on biodiversity and food security[edit]

Main articles: biodiversity and food security


Limiting factors[edit]



Mythical, legendary and religious hybrids[edit]

Main article: Mythological hybrid

Ancient folktales often contain mythological creatures, sometimes these are described as hybrids (e.g., hippogriff as the offspring of a griffin and a horse, and the Minotaur which is the offspring of Pasiphaë and a white bull). More often they are kind of chimera, i.e., a composite of the physical attributes of two or more kinds of animals, mythical beasts, and often humans, with no suggestion that they are the result of interbreeding, e.g., harpies, mermaids, and centaurs.

In the Bible, the Old Testament contains several passages which talk about a first generation of hybrid giants who were known as the Nephilim.[49] The Book of Genesis (6:4) states that "the sons of God went to the daughters of humans and had children by them". As a result, the offspring was born as hybrid giants who became mighty heroes of old and legendary famous figures of ancient times.[50] In addition, the Book of Numbers (13:33) says that the descendants of Anak came from the Nephilim, whose bodies looked exactly like men, but with an enormous height. According to the apocryphal Book of Enoch the Nephilim were wicked sons of fallen angels who had lusted with attractive women.[51]

See also[edit]


  1. ^ "Hybrid". Merriam Webster. Retrieved 2014-06-12. 
  5. ^ askoxford.com
  6. ^ Oxford English Dictionary Online, Oxford University Press 2007.
  7. ^ "When the sire is a lion the result is termed a Liger, whilst the converse is a Tigon." Edward George Boulenger, World natural history, B. T. Batsford ltd., 1937, p. 40.
  14. ^ Rong, R; Chandley, A. C.; Song, J; McBeath, S; Tan, P. P.; Bai, Q; Speed, R. M. (1988). "A fertile mule and hinny in China". Cytogenetics and cell genetics. 47 (3): 134–9. doi:10.1159/000132531. PMID 3378453. 
  15. ^ Esch, Mary. "Study: Eastern wolves are hybrids with coyotes". Associated Press. [dead link]
  20. ^ Soubrier, Julien; Gower, Graham; Chen, Kefei; Richards, Stephen M.; Llamas, Bastien; Mitchell, Kieren J.; Ho, Simon Y. W.; Kosintsev, Pavel; Lee, Michael S. Y. (2016-10-18). "Early cave art and ancient DNA record the origin of European bison". Nature Communications. 7. doi:10.1038/ncomms13158. ISSN 2041-1723. 
  21. ^ Daley, Jason. "Cave Paintings Help Unravel the Mystery of the 'Higgs Bison'". Smithsonian. Retrieved 2016-10-20. 
  24. ^ Amphibians.org May 2014 Godzilla vs. Godzilla—How the Chinese Giant Salamander is taking a toll on its Japanese Comic Counterpart
  26. ^ Grula, John W.; Taylor, Orley R. (1980). "The Effect of X-Chromosome Inheritance on Mate-Selection Behavior in the Sulfur Butterflies, Colias eurytheme and C. Philodice". Evolution. 34 (4): 688–95. doi:10.2307/2408022. 
  27. ^ "Lilium Hybrids". Pacific Bulb Society. Retrieved 2015-03-22. 
  29. ^ University of Colorado Principles of Genetics (MCDB 2150) Lecture 33: Chromosomal changes: Monosomy, Trisomy, Polyploidy, Structural Changes Archived 14 October 2012 at the Wayback Machine.
  30. ^ "Evaluating the utility of Arabidopsis thaliana as a model for understanding heterosis in hybrid crops", Euphytica, Springer Netherlands, 156 (1-2): 157–171, July 2007, doi:10.1007/s10681-007-9362-1, ISSN 0014-2336 
  31. ^ Rieseberg, Loren H.; Margaret A. Archer; Robert K. Wayne (July 1999). "Transgressive segregation, adaptation and speciation". Heredity. 83 (4): 363–372. doi:10.1038/sj.hdy.6886170. PMID 10583537. 
  33. ^ a b c d Allendorf, Fred W.; R.F. Leary; P. Spruell; J.K. Wenburg (November 2001). "The problems with hybrids: setting conservation guidelines". TRENDS in Ecology & Evolution. 16 (11): 613–622. doi:10.1016/S0169-5347(01)02290-X. 
  37. ^ Ehrlich, Paul; John Holdren (26 March 1971). "Impact of population Growth". Science. 171 (3977): 1212–1216. doi:10.1126/science.171.3977.1212. 
  38. ^ Vitousek, Peter; Carla M. D'Antonio; Lloyd L. Loope; Marcel Rejmánek; Randy Westbrooks (1997). "Introduced Species: A Significant Component of Human-cause Global Change". New Zealand Journal of Ecology. 21 (1): 1–16. 
  44. ^ Rhymer, JM; Simberloff, D (1996). "Extinction by Hybridization and Introgression". Annual Review of Ecology and Systematics. 27: 83–109. doi:10.1146/annurev.ecolsys.27.1.83. 
  46. ^ Devinder Sharma "Genetic Pollution: The Great Genetic Scandal" Archived 18 May 2009 at the Wayback Machine.; Bulletin 28. hosted by www.farmedia.org
  48. ^ "Barriers to hybridization of Solanum bulbocastanumDun. and S. VerrucosumSchlechtd. and structural hybridity in their F1 plants", Euphytica, Springer Netherlands, 25 (1): 1–10, January 1976, doi:10.1007/BF00041523, ISSN 0014-2336 

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