Gene flow

transfer of genetic variation from one population to another

Gene flow or gene migration is the name for the transfer of alleles or genes from one population to another. The most usual cause is the movement of animals or (with plants) the movement of seeds or fruits.

Various barriers to gene flow can occur. The most usual is a geographical barrier of some kind. The beginnings of speciation often depends on the separation of populations which were once interbreeding (panmictic).