Hi Bluejay.
Given all the subjectivity involved in biological definitions, I’m not sure we can actually say that hybridization really means all that much. Hybrid is, itself, a rather vague term, defined as the fusion of two other things that were previously classified as distinct from one another based on equally vague and subjective terms.
I'm surprised that nobody has mentioned hybrids between varieties within a species, as this is well known and often used in breeding.
Heterosis - Wikipedia
quote:
Heterosis is a term used in genetics and selective breeding. The term heterosis, also known as hybrid vigor or outbreeding enhancement, describes the increased strength of different characteristics in hybrids; the possibility to obtain a genetically superior individual by combining the virtues of its parents.
Heterosis is the opposite of inbreeding depression, which occurs with increasing homozygosity. The term often causes controversy, particularly in terms of the selective breeding of domestic animals, because it is sometimes believed that all crossbred plants or animals are genetically superior to their parents; this is true only in certain circumstances: when a hybrid is seen to be superior to its parents, this is known as hybrid vigor. When the opposite happens, and a hybrid inherits traits from their parents that makes them unfit for survival, the result is referred to as outbreeding depression. Typical examples of this are crosses between wild and hatchery fish that have incompatible adaptations.
Dogs are probably the best example of hybridization between varieties.
The other place where we see hybridization being important is in hybrid zones between varieties of a species, where gene flow occurs between what would otherwise be isolated populations in a small area where the populations overlap. You could have a linear distribution of population centers and multiple hybrid zones between them to maintain gene flow, however the rate of flow is unlikely to keep the ends of the distribution from diverging. When we talk about ring species we see situations where the linear distribution folds back on itself and ends up with varieties that overlap but don't hybridize.
Perdition,
Message 7: As a complete layman, I've always assumed hybrids are a result of two recently diverged lineages. If they're both still near the "fork in the river" so to speak, they have enough similarities to overcome the differences that are building up.
Or diverging populations, where speciation has not occurred yet but is immanent. If the isolation of the main populations increases and the hybrid zones become smaller so gene flow slows, the interfertility between the populations decreases as they accumulate mutations that are increasingly incompatible.
Thus hybridization can be seen as attempts to reunite populations that have become estranged, possibly resulting in some varieties showing hybrid vigor that can also increase and either draw the populations back together or meld with one or the other population. Lots of possibilities here.
Enjoy.
we are limited in our ability to understand
by our ability to understand
Rebel American Zen Deist
... to learn ... to think ... to live ... to laugh ...
to share.
• • • Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click) • • •
™ Version 4.2
(1)
