Secondary contact

Secondary contact is the process by which two populations of a species that have been geographically separated, or allopatric, come back into contact with one another. It creates the potential for gene exchange between them, depending on how reproductively isolated the populations have become in the meantime. The main outcomes of secondary contact include the extinction of one population, the fusion of the two populations back into one, reinforcement of reproductive isolation, the formation of a hybrid zone, or the formation of an entirely new species through hybrid speciation. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/