Polyploidy in plants leads to sympatric speciation. Sympatric speciation occurs in sympatric populations without geographical isolation of the species. It arises due to some biological barrier to interbreeding. If the hybrid between two deplored species becomes tetreploid, it becomes reproductively isolated from its diploid parents, because the triploid offsprings produced by back crossing produce high ratio of aneuploids gametes which fail to survive.
Organisms with three or more genomes are polyploids. Fully one half of all known plant genera contain polyploids, and about two third of all the grasses are polyploids, polyploids are rarely seen in animals. Two main kinds of polyploids, autopolyploids and allopolyploids, may be distinguished on the basis of their source of chromosomes. Two basic irregular processes have been discovered by which polyploids may evolve from diploid plants and become established in nature.