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Hybrid incompatibility occurs when the offspring of two closely related species are not viable or suffer from infertility. Charles Darwin posited that hybrid incompatibility is not a product of natural selection, stating that the phenomenon is an outcome of the hybridizing species diverging, rather than something that is directly acted upon by selective pressures. [4]
Namely, if selection reinforces the degree of reproductive isolation that exists between two species due to the poor adaptive value of the hybrids, it is expected that the populations of two species located in the same area will show a greater reproductive isolation than populations that are geographically separated (see reinforcement).
Hybrid speciation in animals is primarily homoploid. While thought not to be very common, a few animal species are the result of hybridization, mostly insects such as tephritid fruitflies that inhabit Lonicera plants [20] and Heliconius butterflies, [21] [22] as well as some fish, [15] one marine mammal, the clymene dolphin, [23] a few birds.
This is a list of genetic hybrids which is limited to well documented cases of animals of differing species able to create hybrid offspring which may or may not be infertile. Hybrids should not be confused with genetic chimeras , such as that between sheep and goat known as the geep .
If their reproductive isolation is incomplete, then further mating between the populations will produce hybrids, which may or may not be fertile. If the hybrids are infertile, or fertile but less fit than their ancestors, then there will be further reproductive isolation and speciation has essentially occurred, as in horses and donkeys. [47]
Human-alien hybrids fill science fiction stories, and the most famous of these is Mr. Spock from Star Trek — the logical science officer of the starship Enterprise.
A mule is a sterile hybrid of a male donkey and a female horse.Mules are smaller than horses but stronger than donkeys, making them useful as pack animals.. In biology, a hybrid is the offspring resulting from combining the qualities of two organisms of different varieties, subspecies, species or genera through sexual reproduction.
Undoubtedly, some people will balk at this advance, viewing it as unnatural and thus, somehow, suspect. But not so long ago, many people viewed all assisted reproduction with suspicion or doubt ...