In which type of speciation does a new species arise without geographical separation?

Sympatric speciation occurs when a new species forms from a single ancestral species while inhabiting the same geographical area. This process typically involves mechanisms such as polyploidy, sexual selection, or habitat differentiation, which lead to reproductive isolation without physical barriers separating the populations.

For instance, in plants, a species may undergo polyploidy, where chromosome duplication results in individuals that can no longer successfully reproduce with the original population, eventually leading to the formation of a new species. In animals, variations in mating preferences can lead to behavioral isolation, causing different groups within the same environment to diverge genetically over time.

In contrast, allopatric speciation requires geographical separation leading to the formation of new species due to isolation. Divergent evolution describes the process where two related species diversify as they adapt to different environments, while adaptive radiation involves the rapid diversification of a lineage into a variety of forms to exploit different ecological niches, usually following a significant event that reopens habitats.