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The mechanisms of reproductive isolation have been classified in a number of ways. Zoologist Ernst Mayr classified the mechanisms of reproductive isolation in two broad categories: pre-zygotic for those that act before fertilization (or before mating in the case of animals) and post-zygotic for those that act after it. [5]
[5] [3]: 369 That is, if gene flow is not zero (if hybrids aren't completely unfit), selection cannot drive the fixation of alleles for prezygotic isolation. [28] For example: If population has the prezygotic isolating allele and the high fitness, post-zygotic alleles and ; and population has the prezygotic allele a and the high fitness, post ...
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 ...
An example of ethological isolation in Ophrys apifera where the orchids structure mimics that of a female bee to attract the male counterparts. Floral Isolation is a form of reproductive isolation found in angiosperms. Reproductive isolation is the process of species evolving mechanisms to prevent reproduction with other species.
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]
Testing the role of natural selection in parallel speciation have focusing on the reinforcement of premating isolation. [2] But for the reinforcement, the requirement is preexisting reproductive isolation in the form of decreased hybrid fitness and is normally considered a final stride towards the process of speciation.
Three-spined stickleback fish have been a frequently studied species in ecological speciation.. Ecological speciation is a form of speciation arising from reproductive isolation that occurs due to an ecological factor that reduces or eliminates gene flow between two populations of a species.
This occurs when the populations already have some reproductive isolation, but still hybridize to some extent. Because hybridization is costly (e.g. giving birth and raising a weak offspring), natural selection favors strong isolation mechanisms that can avoid such outcome, such as assortative mating. [5]