Hybrid speciation

Hybrid speciation is the process wherein hybridization between two different species leads to a distinct phenotype. This phenotype can also be fitter than the parental lineage and as such natural selection may then favor these individuals. Eventually, if reproductive isolation is achieved, it may lead to a separate species. However, reproductive isolation between hybrids and their parents is particularly difficult to achieve and thus hybrid speciation is considered an extremely rare event.

Hybridization without change in chromosome number is called homoploid hybrid speciation. It is considered very rare but as been shown in Heliconius butterflies and in sunflowers. Polyploid speciation, which involves changes in chromosome number, is a more common phenomena, especially in plant species.