hybrid

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Cymbidium Doris, an Orchid Grex , emerged as a hybrid of Cymbidium insigne and Cymbidium tracyanum

A hybrid (also the hybrid , the hybrid ) or natural hybrid is in biology an individual that has emerged from sexual reproduction between different genera , species , subspecies , ecotypes or populations .

In controlled breeding , the term is used for the offspring of crosses of different breeds or lines .

Linguistic

Word origin and word forms

Hybrid goes back to the Latin hybrida (also: hibrida or ibrida ) "mixed breed". This is etymologically generally related to the Greek ὕβρις hybris ("arrogance", "arrogance"), although the exact origin of the Latin hybrida is unclear. According to the Latin texts including a hybrid made was probably first specifically wild boar and domestic pigs (as in the understood and the concept transferred later to other hybrids and hybrids Naturalis Historia of Pliny the Elder ).

The adjective hybrid means something like "composed of different things". There is also an identical adjective hybrid with the meaning “haughty”, which belongs to the noun hubris .

The noun hybrid is mainly used as a feminine , but also as a masculine : the hybrid , more rarely the hybrid . The two-syllable word form (the) hybrid is also used. Accordingly, two plural forms are used : the hybrids or the hybrids . With hybrid , numerous compounds are formed (e.g. hybrid corn ), also in other sciences.

Use of terms

In breeding practice, the term hybrid was originally used primarily in plant breeding . First two inbred lines of a breed are selected and then certain characteristics are reinforced over many generations through conscious inbreeding and subsequent selection.

In animal breeding, poultry and pigs are also named with the addition of hybrid . However, in the narrower sense of the word, these are crossings of uses . To produce inbred products with a sufficiently high homozygosity would be too expensive in terms of both time and money, since it is not foreseeable beforehand whether the cross-breeding products would produce correspondingly higher performance.

To distinguish the artificially created hybrids, breeders also refer to the crosses that have arisen in nature without human intervention (especially with plants) as natural hybrids .

Synonyms

Non-technical or outdated terms with the same meaning as hybrids are: Bastard , Mischling or Blendling .

However, the terms mongrel or bastard are still used in animal breeding (the latter also in heraldry ) without expressing a negative evaluation, which they often have in everyday language.

Differentiation from chimeras

Hybrids are to be distinguished from chimeras . A chimera is understood to be an organism that is made up of genetically different cells or tissues, with the cells originating from different fertilized egg cells. In contrast to hybrids, chimeras do not go back to sexual reproduction. Chimeras can arise as a result of organ transplants or in plant breeding during grafting . They are often produced using genetic engineering methods. Despite these differences, chimeras are occasionally referred to as “hybrid” organisms because they are also genetically mixed beings.

Importance for hybrid breeding

Fertility

If there is a cross between different species - mostly the species are closely related - then we speak more specifically of species hybrids. Species hybrids are often not fertile or are only partially fertile , but there are a number of exceptions. If a hybrid stabilizes in the successive generations and achieves full fertility, for example by doubling the set of chromosomes, a new species has emerged from the hybrid. One speaks of a hybrid species or an alloploid species.

Hybrids whose parents belong to the same species (i.e. simply represent different genetic lines, varieties or races) are usually fertile; however, according to Mendelian rules , the characteristics are split up from the next generation (F2 generation).

Hybrid formation is of practical importance in breeding research, especially for cultivated plants, but breeding animal breeds also often cross breeds into another, with the genetic traits intermingling.

vitality

Hybrid breeding avoids inbreeding problems, see inbreeding depression . In hybrid plant breeding , the heterosis effect is used , which - compared to pure- breeding organisms - leads to more vitality and productivity. The heterosis effect can, for example, lead to a doubling of yields in cereal species such as maize . Accordingly, the proportion of hybrid varieties has risen sharply in the last few decades. In 1995 for broccoli , tomatoes and Brussels sprouts , over 80% of the varieties were hybrid varieties. In the US, hybrids are used on more than 90% of the corn acreage. In China, more than half of the rice area is sown with hybrids. Rice hybrids are in the test phase in 16 Asian countries. In India, more than a third of the cotton area is hybrids.

In order to fully utilize the heterosis effect, pure-bred inbred lines are used as the parent generation in hybrid breeding . The resulting line hybrids form the first branch generation (F1 generation). They are known as F1 hybrids and are genetically uniform.

The offspring of hybrids lose a lot of fitness , for example the yield of maize is reduced by around 30% if the seed was produced from hybrids. The usual seed price is only part of this loss of income, which is why the annual seed purchase is worthwhile from an economic point of view. The incentive for seed manufacturers to develop improved varieties for open pollination is diminishing because of the benefits of hybrid breeding. In addition, openly pollinated improved varieties can lose their breeding advantages through crossing, especially if they are grown into unimproved varieties close to the field.

Significance for evolution

Hybrid formation is also important in the natural evolutionary processes of biological species and thus for the establishment of genetic diversity within species. While the emergence of new species through species hybridization in higher plants has been common and known for a long time, it was rarely observed in animals for a long time. However, natural hybridization of species does occur throughout the animal kingdom. However, animal hybrids are often not easy to recognize in terms of their phenotype and are often only discovered using methods of genetic analysis.

In general, there is a tendency to be observed that young species in particular can hybridize in nature, provided there are opportunities for contact, although this process often does not lead to a general mixing and blurring of the species boundaries, but to the formation of so-called hybrid zones. The resulting hybrid species are partly sterile ; in this case they are of no relevance to the evolutionary process. Well-known examples are the mule and mule , two crossbreeds of domestic horse and domestic donkey. In some cases, however, they are quite fertile and form the basis for the emergence of new genotypes and species, as has been shown for example for snails, water fleas or birds. From brown bear and polar bear also fertile hybrids in nature are now proven.

Hybrid formation also played a role in the evolution to modern humans: Genetic studies of the human tribal history have shown evidence of repeated crossings between human and chimpanzee ancestors - around ten to six million years ago - over a period of around four million Years ago. The evidence found in the genome of modern humans to a hybridization with the Neanderthals and the Denisova humans some ten thousand years ago was referred to in a more recent work.

In general, all allopolyploid species are the results of previous hybridizations. This applies to both bred and naturally allopolyploid animal and plant species. Such cases have been detected among plants, for example in the genus Nicotiana or in rapeseed ( Brassica napus ). There is corresponding evidence for animals, for example for freshwater snails.

Examples from the flora and fauna

Hybrids are identified by a × (not the small letter x). In species hybrids this small cross is placed between the parent species names, in genus hybrids in front of the two genus names.

plants

The images show two orchid species (parent species) on the left and right and their natural hybrids in between, which in this case are even genus hybrids (although, according to more recent findings, both species probably belong to the same genus):

Another example, also a generic hybrid, is the ornamental shrub × Chitalpa tashkentensis .

Animals

  • In the birds, hybrids in approx. 4000 species combinations have so far been detected, whereby approx. 2000 cases are hybrids that were created in human care. The actual number of species combinations is estimated to be much higher, as hybrids are sometimes difficult to recognize.
  • The Spatula skua ( Stercorarius pomarinus ) and the Italian sparrow ( Passer italiae ) have sometimes been suspected of being hybridogenic.
  • The emperor pheasant was considered extinct for a long time and was only identified as a rare hybrid between Edward's and silver pheasant in 2003.
  • The rackel hen always comes from a capercaillie and a black grouse. The reverse combination (black grouse and capercaillie) does not occur in natural conditions because of the size difference.
  • The pond frog ( Pelophylax "esculentus" ) is a hybridogenic hybrid of the sea ​​frog ( Pelophylax ridibundus ) and the small water frog ( Pelophylax lessonae ) and can survive and reproduce in nature. It is not even necessary for one of the two parent species to exist in the same biotope ( triploid individuals of the pond frog can take over their genetic function ).
  • The honeysuckle maggot ( Rhagoletis mendax × zephyria ) evidently evolved as a new species from its two parent species over the course of about 250 years.
  • In water fleas (species of the genus Daphnia ) species hybrids have been proven on various occasions.
  • Mountain hare and brown hare can have fertile offspring together.
  • Camas are a cross between old world camel and lama.
  • Schiegen are a cross between a sheep and a goat.
  • In terms of mitochondrial DNA, bison are closer to representatives of the genus Bos than the American bison and the yak , which is why it is assumed that the bison is a hybrid species. According to this, prehistoric bison bulls mated again and again with aurochs or related cattle, from which the bison emerged in the Holocene .
Hybrid between horse and zebra: Zorse , 1899
  • Zebroids are crosses of zebras and other animals of the horse genus.
  • Mules are a cross between a horse mare and a donkey stallion.
  • Mules are a cross between a donkey mare and a horse stallion.
  • " Motty " was a hybrid elephant (African and Asian elephant, Loxodonta africana × Elephas maximus ) born in 1978 at Chester Zoo (Great Britain ).
  • Hybrid dogs (planned crossing) and mixed breed dogs ( not planned crossing)
  • The poodle wolf is a cross between a male king poodle and a she-wolf. It was bred in the 1960s for behavioral research (wolf father and royal poodle mother make a "Wopu").
  • Coydog, Coywolve and Coywolf are US names for crossbreeds of coyotes with domestic dogs or wolves.
  • Big cat hybrids : An example is the cross between a lion and a tiger ( i.e. a liger or a töwe ).
  • Small cat hybrids: One example is the Savannah cat ( Felis catus × Leptailurus serval ), a cross between a domestic cat and a serval
  • Pizzly : On April 16, 2006, a polar bear with a slightly brownish fur was shot in the Canadian Arctic . Genetic tests showed that this was the first mixed breed of polar bear and grizzly to be found in the wild . It has long been known from zoological gardens that both species of bears can produce offspring together. In nature, however, aggressive confrontations were regularly observed when both species met by chance.
  • A Wholphin is a rare cross between a bottlenose dolphin with a small whale .

Web links

Commons : Hybrids  - collection of images, videos and audio files
Wiktionary: Hybrids  - explanations of meanings, word origins, synonyms, translations
Wiktionary: Mischling  - explanations of meanings, word origins, synonyms, translations

Individual evidence

  1. ↑ a b c Cf. Duden online: Hybride .
  2. ^ Gerhard Wagenitz : Dictionary of Botany. Morphology, anatomy, taxonomy, evolution. 2nd, expanded edition. Nikol, Hamburg 2008, ISBN 978-3-937872-94-0 .
  3. ↑ entry hibrida or hybrida (IBR) in: Charlton T. Lewis, Charles Short, A Latin Dictionary . Oxford, Clarendon Press, 1879.
  4. ↑ hybrid in the Online Etymology Dictionary, quotation: “of unknown origin but probably from Greek and somehow related to hubris ”.
  5. ↑ See entry hybrid in Walter William Skeat: An etymological dictionary of the English language . Oxford: Clarendon Press, 1888: Origin "somewhat unclear" (somewhat doubtful) .
  6. ^ Minton Warren (1884): On the Etymology of Hybrid (Lat. Hybrida) American Journal of Philology 5 (4): 501 f.
  7. ↑ Duden online: hybrid (mixed).
  8. ↑ Duden online: hybrid (haughty, arrogant).
  9. ↑ Jürgen Wolfgang Weiß, Wilhelm Pabst, Susanne Granz: Tierproduktion , Georg Thieme Verlag, 2013, Chapter 4.1.2 Systematic crossbreeding ( limited preview in the Google book search).
  10. ^ JH Kaltschmidt: Comparative dictionary of the German language. P. 165.
  11. ↑ On the terms hybrid and chimera cf. Josef Kuře: Etymological background and further clarifying remarks . Chapter 1 in Jochen Taupitz, Marion Weschka (Editor): Cimbrids - Chimeras and Hybrids in Comparative European and International Research: Scientific, Ethical, Philosophical and Legal Aspects. Springer, 2009, ISBN 978-3-540-93869-9 .
  12. ↑ A. Basra (1999): Heterosis and hybrid seed production in agronomic crops. Routledge.
  13. ↑ K. Schwenk, N. Brede, B. Streit (2008): Introduction. Extent, processes and evolutionary impact of interspecific hybridization in animals. Phil. Trans. R. Soc. B: 363: pp. 2805-2811.
  14. ↑ Süddeutsche Zeitung No. 291 of December 16, 2010.
  15. ↑ Nick Patterson, Daniel J. Richter, Sante Gnerre, Eric S. Lander, David Reich (2006): Genetic evidence for complex speciation of humans and chimpanzees . In: Nature , Vol. 441 (June 29, 2006), pp. 1103-1108.
  16. ↑ Science 328, Issue 5979, pp. 710-722 (2010).
  17. ^ B. Streit, Th. Städler, K. Schwenk, A. Ender, K. Kuhn, B. Schierwater (1994): Natural hybridization in freshwater animals: Ecological implications and molecular approaches. Science 81: 65-73.
  18. ↑ EM Mc Charty: Handbook of Avian Hybrids of the World. Oxford University Press, Oxford 2006. ISBN 0-19-518323-1
  19. ↑ A. Hobæk, M. Skage, K. Schwenk: Daphnia galeata × D. longispina hybrids in western Norway. In: Hydrobiologia. Volume 526, 2004, pp. 55-62.
  20. ↑ Bengt Lindlöf: Lär känna skogsharen . Stockholm: Svenska jägareförbundet 1987, p. 11 (Swedish).
  21. ↑ Verkaar ELC, Nijman IJ, Beeke M, Hanekamp E, Lenstra JA: Maternal and paternal lineages in cross-breeding bovine species: has wisent a hybrid origin? Mol Biol Evol 2004 (21): 1165-1170.
  22. ↑ Motty, the crossbreed African and Asian elephant. Archived from the original on November 13, 2003 ; accessed on March 1, 2015 .
  23. ↑ Nature Vol. 441 of May 18, 2006, p. 268
  24. ↑ Süddeutsche Zeitung No. 112 of May 16, 2006, p. 22