EN
The evolutionary importance of natural interspecific hybridisation is still an issue of debate. The application of molecular tools in population genetic studies unraveled that hybridization is more frequent than prevoiusly expected. It seems that 6-25% species hybridize, within both plants and animals, although the numbers given may represent substantial underestimate. It is still not resolved how many species is of hybrid origin. Due to the widespread of hybridization discovered, questions on its importance for ecology, evolution and conservation of species have to be re-examined. The controversy whether the hybrids are fit or unfit relative to their parents seems to be of major ecological importance. On the other hand, it has been proven that hybridization enhances speciation and diversification of species. The are two issues critical for the success and importance of hybridization: 1) the stability of genetical architecture after mixing of gene pools of the two different species, 2) the interplay between hybrid phenotype and environmental conditions. The hybridization may facilitate speciation due to transgressive segregation, increased phenotypic variation or phenotypic plasticity. Broad range of phenotypes allows natural selection to play upon it, and makes it more feasible to pick-up the most fit ones. Thus hybridization may be important mechanism for colonization of new environments, creating new ecological niches, or fastening evolutionary changes.