What is the process called where populations in the same area become reproductively isolated?

The process where populations in the same area become reproductively isolated is known as sympatric speciation. This occurs when groups within a species diverge into two or more distinct species while living in the same geographic region. This type of speciation can happen through various mechanisms such as behavioral isolation, temporal isolation, or habitat differentiation, where different behaviors or preferences for certain resources or habitats lead to reproductive barriers.

In sympatric speciation, despite the physical proximity, genetic divergence can arise due to ecological differences or changes in mating preferences, which prevent interbreeding among the distinct groups. This contrasts with allopatric speciation, where populations become isolated due to physical barriers, leading to reproductive isolation over time. Understanding this concept is crucial because it highlights the importance of ecological and behavioral factors in the evolution of species.