Why is reproductive isolation between intraspecific cytotypes so important? A commentary on: 'Strong post-pollination interactions govern cytotype isolation in a tetraploid-octoploid contact zone'
Abstract
Polyploidization is widely recognized as an important and almost 'instantaneous' mechanism of sympatric speciation in plants. Indeed, the process of whole genome duplication directly provides first-generation polyploid mutants with postzygotic reproductive isolation (RI) from their diploid progenitors.
As a consequence, most mating attempts between diploids and polyploids will result in interploidy hybrids with limited viability and/ or fertility (the result of the so-called 'triploid block'). However, the evolutionary success of newly formed polyploid lineages depends mainly on whether additional prezygotic RI is formed, allowing polyploid mutants to locally establish and further spread.
For this reason, exploring the efficiency of prezygotic RI and its mechanisms are crucial steps towards understanding polyploid evolution. The study of Castro et al. (2020) in this issue of Annals of Botany provides such estimates across multiple reproductive barriers between tetraploid and octoploid cytotypes of Gladiolus communis in their contact zone on the Iberian Peninsula.