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Reproductive isolation between species appears, in certain cases, a long time after fertilization and the formation of the zygote, as happens – for example – in the twin species Drosophila pavani and D. gaucha. The hybrids between both species are not sterile, in the sense that they produce viable gametes, ovules and spermatozoa.
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.
Introduced to the scientific community in the early 1990s, the concept of cryptic female choice is complicated and offers a new explanation for infertility. [1] Non-additive genetic effects have been thought of to be the main reason for reproductive isolation between species. [2]
Reinforcement is a process of speciation where natural selection increases the reproductive isolation (further divided to pre-zygotic isolation and post-zygotic isolation) between two populations of species. This occurs as a result of selection acting against the production of hybrid individuals of low fitness.
Reproductive isolation occurs upon the formation of a hybrid zone. In most cases, [citation needed] the hybrid zone is eliminated due to a selective disadvantage. This effectively completes the speciation process. In parapatric speciation, two subpopulations of a species evolve reproductive isolation from one another while continuing to ...
Peripatric speciation is a mode of speciation in which a new species is formed from an isolated peripheral population. [1]: 105 Since peripatric speciation resembles allopatric speciation, in that populations are isolated and prevented from exchanging genes, it can often be difficult to distinguish between them, [2] and peripatric speciation may be considered one type or model of allopatric ...
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.
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]