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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]
The barrier of hybrid inviability occurs after mating species overcome pre-zygotic barriers (behavioral, mechanical, etc.) to produce a zygote. The barrier emerges from the cumulative effect of parental genes; these conflicting genes interfere with the embryo's development and prevents its maturation. Most often, the hybrid embryo dies before ...
[3]: 362 Jerry Coyne and H. Allen Orr surveyed 171 species pairs, collecting data on their geographic mode, genetic distance, and strength of both prezygotic and post-zygotic isolation; finding that prezygotic isolation was significantly stronger in sympatric pairs, correlating with the ages of the species.
Reinforcement, under his definition, included prezygotic divergence and complete post-zygotic isolation. [18] Servedio and Noor include any detected increase in prezygotic isolation as reinforcement, as long as it is a response to selection against mating between two different species. [4]
A postzygotic mutation (or post-zygotic mutation) is a change in an organism's genome that is acquired during its lifespan, instead of being inherited from its parent(s) through fusion of two haploid gametes. Mutations that occur after the zygote has formed can be caused by a variety of sources that fall under two classes: spontaneous mutations ...
Prezygotic incompatibilities - reproductive barrier acting before fertilization. For example, pollinator isolation, mechanical barriers preventing mating, and sperm/ovule incompatibilities that prevent fertilization. Reproductive isolation - the presence of barriers to successful crossbreeding. Barriers can be classified in a number of ways ...
Despite being one of the most studied factors in ecological speciation, many aspects are still less understood such as how prevalent the process is in nature [4] as well as the origin of barriers for post-zygotic isolation (as opposed to the much easier detectable pre-zygotic barriers).
All three species are separated by intrinsic reproductive barriers [1] Secondary contact is the process in which two allopatrically distributed populations of a species are geographically reunited. This contact allows for the potential for the exchange of genes, dependent on how reproductively isolated the two populations have become.