Search results
Results From The WOW.Com Content Network
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.
Support for the reproductive character displacement hypothesis comes from observations of sympatric species in overlapping habitats in nature. Increased prezygotic isolation, which is associated with reproductive character displacement, has been observed in cicadas of genus Magicicada, stickleback fish, and the flowering plants of the genus Phlox.
The varying definitions of sympatric speciation fall generally into two categories: definitions based on biogeography, or on population genetics. As a strictly geographical concept, sympatric speciation is defined as one species diverging into two while the ranges of both nascent species overlap entirely – this definition is not specific ...
Ernst Mayr proposed the widely used Biological Species Concept of reproductive isolation in 1942. Most modern textbooks make use of Ernst Mayr's 1942 definition, [62] [63] known as the biological species concept, as a basis for further discussion on the definition of species. It is also called a reproductive or isolation concept.
A mode of speciation where the evolution of reproductive isolation is caused by the geographic separation of two or more populations of a single species. [5] allopatric taxa Specific species that are allopatrically distributed. allopatry The phenomenon by which two or more populations of a single species exist in geographic isolation from one ...
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.
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]
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]