is the process that occurs when two groups of organisms become incapable of successfully interbreeding even when they are not separated by geography. (Thought to result from restricted gene flow).

Sympatric speciation

Explanation:

Reproductive isolation is the phenomena where two groups of organisms are not able to interbreed because of many mechanical, spatial or temporal barriers. It ultimately leads to formation of two different species. It can occur by allopatric speciation or sympatric speciation.

In allopatric speciation, the groups are not able to interbreed because they are geographically isolated. However sympatric speciation occurs in the same geography. The two groups inhabit the same area but are still not able to interbreed because gene flow is prevented between them. For example, in plants polyploidy can occur due to random mutation. Such a plant will not be able to mate with other plants of same species in the same area because of different chromosome number. Hence, it becomes reproductively isolated from rest of the plants in the area.