The process of evolution of different species in a given geographical area starting from a point and literally radiating to other areas of geography (habitats) is called Adaptive Radiation.

During his journey Darwin went to Galapagos Islands. There he observed an amazing diversity of creatures. Small black birds later called Darwin’s Finches amazed him. He realised that there were varieties of finches in the same island.

From the original seed-eating features , many evolved on the island itself. From the original seed-eating features, many other forms with altered beaks arose, enabling them to become insectivorous and vegetarian finches. This process is called adaptive radiation.

“The principle of adaptationism has been adopted so widely by Darwinians because it is such a heuristic methodology.”

“Adaptive radiation refers to the adaptation (via genetic mutation) of an organism which enables it to successfully spread, or radiate, into other environments.”

Darwin’s finches represent one of the best examples of this phenomenon. Another example if Australian marsupials. A number of marsupials, each different from the other evolved from an ancestral stock, but all within the Australian island continent.

When more than one adaptive radiation appeared to have occurred in an isolated geographical area( representing different habitats) , one can call this convergent evolution.

Placental mammals in Australia also exhibit adaptive radiation in evolving into varieties of such placental mammals each of which appears to be ‘similar’ to a corresponding marsupial.

“Speciation is the development of one of multiple new species in the evolutionary process, where the original species produces mutated forms which successfully survive in other environments due to these mutations.”

“Phylogenetics is the study of the evolutionary steps a species has taken during the process of speciation.”

https://biologydictionary.net/adaptive-radiation/

https://www.sparknotes.com/biology/evolution/speciation/section3/