Answer:
Speciation has definitely occurred when two groups of related organisms can not interbreed to produce fertile progeny.
Step-by-step explanation:
Species is a group of individuals that can interbreed among themselves and produce fertile progeny. A species is reproductively isolated from other species, that is, members of one species can not interbreed with that of other species to produce fertile progeny. Therefore, if two groups of related organisms are reproductively isolated, they are considered as being two separate species.