In the process of biological speciation, two populations of a species become geographically isolated (often by a physical barrier such as a river or mountain range). Over time, these two populations diverge genetically and adapt to their specific environments,
until they become so distinct that they can no longer interbreed. At this point, they are considered separate species.
Sibling species often look very similar to each other, but can be distinguished by small genetic differences or ecological/behavioral traits. In some cases, sibling species can even live in the same geographic area and not interbreed due to differences in mating preferences or timing.
The presence of sibling species is a reminder that speciation is an ongoing process and that even closely related species can continue to evolve and diverge over time. Studying sibling species can help scientists understand how evolutionary processes have shaped the biodiversity of life on Earth.