Interbreeding species concept-species concepts is not very useful in defining plant species because some plant groups readily hybridize with other plant groups. The biological species concept holds that organisms are members of a common species if they can interbreed and result in live, fertile offspring. Prezygotic and postzygotic obstacles separate species from one another and prevent mating or the development of viable, fertile offspring. New species emerge through a process called speciation. It happens when populations of a species diverge and become reproductively isolated. When groups from an ancestral population undergo allopatric speciation, it is because of a period of geographic isolation that they diverge into distinct species. When groups from the same ancestral population evolve into distinct species, there is no geographical separation.
