This process of evolution of a single ancestral species into a variety of species each specialised to exploit a particular ecological niche is termed

Adaptive radiation is the process by which a single ancestral species diversifies into a variety of different species, each of which is specialised to exploit a particular ecological niche. This process typically occurs when a group of organisms undergoes rapid evolutionary diversification in response to new ecological opportunities or changes in their environment. During adaptive radiation, the diversifying species may undergo changes in morphology, behaviour, physiology, and genetics that enable them to exploit new resources or avoid competition with other species. 

The classic example of adaptive radiation is the diversification of the finches on the Galapagos Islands, which occurred over a relatively short period of time and resulted in the evolution of numerous different beak shapes and sizes, each adapted to a different type of food.

‘Saltation’ refers to single step evolution by mutations. Coevolution is the process by which two or more species (e.g., parasite and host) influence each other’s evolution over time.