Interspecific Incompatibility

Abstract

Interspecific incompatibility is defined, in the present review, as any of the post-pollination processes preventing, through an absence of pollen germination or an abnormal behavior of pollen tubes, the formation of hybrid zygotes combining the genomes of two different fertile species or fertile eco types. The phenomenon prevents gene flow between species and, in opposition to the self-incompatibility mechanism restricting inbreeding, establishes upper limits to outbreeding and panmixis. Interspecific incompatibility thus contributes to the isolation of populations and consequently favorizes speciation and the gradual increase of polymorphism within the genus and within the family. It acts essentially as a breeding barrier between sympatric species, but also participates in the rejection of foreign germplasm migrating in the pollen grains from allopatric populations, or to the isolation of invaders introduced as seed.