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The mechanisms of reproductive isolation are a collection of evolutionary mechanisms, behaviors and physiological processes critical for speciation. They prevent members of different species from producing offspring , or ensure that any offspring are sterile.
The Bateson–Dobzhansky–Muller model, [1] also known as Dobzhansky–Muller model, is a model of the evolution of genetic incompatibility, important in understanding the evolution of reproductive isolation during speciation and the role of natural selection in bringing it about.
Ernst Mayr recognised the key importance of reproductive isolation for speciation in his Systematics and the Origin of Species (1942). [45] W. D. Hamilton conceived of kin selection in 1964. [46] This synthesis cemented natural selection as the foundation of evolutionary theory, where it remains today.
Reinforcement is a process within speciation where natural selection increases the reproductive isolation between two populations of species by reducing the production of hybrids. [ 1 ] [ 2 ] Evidence for speciation by reinforcement has been gathered since the 1990s, and along with data from comparative studies and laboratory experiments, has ...
Such isolation may lead to speciation, but this is not guaranteed. Genetic isolates may form new species in several ways: Allopatric speciation, in which two populations of the same species are geographically isolated from one another by an extrinsic barrier and evolve intrinsic (genetic) reproductive isolation.
Eventually, if reproductive isolation is achieved, it may lead to a separate species. However, reproductive isolation between hybrids and their parents is particularly difficult to achieve and thus hybrid speciation is considered an extremely rare event. The Mariana mallard is thought to have arisen from hybrid speciation. [citation needed]
The German evolutionary biologist Ernst Mayr argued in the 1940s that speciation cannot occur without geographic, and thus reproductive, isolation. [29] He stated that gene flow is the inevitable result of sympatry, which is known to squelch genetic differentiation between populations.
Genetic divergence will always accompany reproductive isolation, either due to novel adaptations via selection and/or due to genetic drift, and is the principal mechanism underlying speciation. On a molecular genetics level, genetic divergence is due to changes in a small number of genes in a species, resulting in speciation. [2]