Hybrid speciation

Hybridisation between genetically divergent populations may lead to the formation of new evolutionary lineages. This may occur via duplication of a hybrid's chromosome complement (allopolyploid speciation) or by stabilisation of a fertile hybrid segregant (homoploid hybrid speciation). Although more common in plants, both modes of hybrid speciation also occur in fungi and in animals, including fish, amphibians and insects. The successful origin and establishment of hybrid species is highly dependent on an ability to occupy novel and/or spatially isolated habitats, in order to escape the effects of competition and gene flow from parental species. This ability is favoured by the generation of genetic novelty resulting from the dramatic effects that hybridisation (and genome duplication in allopolyploids) have on modifying genome structure and gene expression. Examples of recently originated allopolyploid and homoploid hybrid species are important models for investigating processes involved in hybrid speciation and establishment.