Many plant species are polyploid or contain polyploid taxa.
Hybrid inviability and sterility cause postzygotic reproductive isolation between polyploids and their diploid ancestors. Computer simulations and field studies in Plantago media have shown that outcrossing tetraploid cytotypes may co-exist with outcrossing diploid cytotypes by flowering time displacement. One very successful way of overcoming hybrid unfitness is the apomictic reproduction seen in triploid Taraxacum officinale. Apomictic reproduction, however, produces genetically uniform offspring that may be less fit in a varying environment. Whether apomixis could evolve in plant species, depends to a large extent on the complexity of the genetic control of apomixis.