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When unique characters develop in a group of species, the species of different characters separate from the main population, creating new species from the existing population. This phenomenon is called speciation.

Formation of barrier, entry to a new niche, genetic polymorphism, isolation, and formation of distinct species are speciation events. These events take millions of years to take.

For example, in allotropic speciation, the formation of a barrier (geographical barrier such as the formation of the mountain) alone takes millions of years.

The isolated species undergo different selective pressure than the main population. It leads to divergence. Speciation is one of the evolutionary processes, as the force of evolution, such as natural selection, acts gradually on the isolated species.

When a group of species isolates due to barriers, the gene pool remains constant. The significant amount of mutation and interspecific reproduction alter the gene pool of the isolated population.

Reportative divergent traits than the parental population occur only after continuous selective pressure, which takes millions of years to occur.

Thus, the time between speciation events takes millions of years due to the constant gene pool. Reproductive divergence will boost the speciation in a rapidly divergent population.