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Speciation is the evolutionary process by which populations evolve to become distinct species. ... If their reproductive isolation was complete, then they will have ...
Controversy exists as to whether Charles Darwin recognized a true geographical-based model of speciation in his publication On the Origin of Species. [5] In chapter 11, "Geographical Distribution", Darwin discusses geographic barriers to migration, stating for example that "barriers of any kind, or obstacles to free migration, are related in a close and important manner to the differences ...
Before speciation is complete, two diverging populations may still produce viable offspring. As speciation progresses, isolating mechanisms – such as gametic incompatibility that renders fertilization of the egg impossible – are selected for in order to increase the reproductive divide between the two populations.
Allopatric speciation (from Ancient Greek ἄλλος (állos) 'other' and πατρίς (patrís) 'fatherland') – also referred to as geographic speciation, vicariant speciation, or its earlier name the dumbbell model [1]: 86 – is a mode of speciation that occurs when biological populations become geographically isolated from each other to an extent that prevents or interferes with gene flow.
The Complete Works of Charles Darwin Online; The Descent of Man, and Selection in Relation to Sex, published in 1871; his second major book on evolutionary theory. History of biology; History of evolutionary thought; History of speciation; Modern evolutionary synthesis; Transmutation of species
The separation decreases the chance of mating to occur between the two populations, inhibiting gene flow, and promoting pre-zygotic isolation to lead to complete speciation. [4] Habitat isolation is not equivalent to a geographic barrier like that of allopatric speciation.
Speciation is the process in which populations within one species change to an extent at which they become reproductively isolated, that is, they cannot interbreed anymore. However, this classical concept has been challenged and more recently, a phylogenetic or evolutionary species concept has been adopted.
These categories are special cases of a continuum from zero (sympatric) to complete (allopatric) spatial segregation of diverging groups. [3] In multicellular eukaryotic organisms, sympatric speciation is a plausible process that is known to occur, but the frequency with which it occurs is not known. [4]