The phenomenon of evolution of different species in a given geographical area starting from a point and spreading to other habitats is called

The process of evolution of different species in a given geographical area starting from a point and literally radiating to other areas of geography is called adaptive radiation.

Saltation is single step large mutation.

When one organism evolves w.r.t evolution in another organism, it is called coevolution. e.g. Host-parasite relationship.

Natural selection is the process through which population of living organisms that adapt are selected by nature based on reproductive fitness.