Sexuality and apomixis in Hieracium are tightly associated with ploidy

Asexual reproduction via seeds (apomixis) is an important speciation mechanism in angiosperms, but its frequency is largely unknown. Mráz and Zdvořák used flow cytometric seed screening to unravel reproductive pathways in more than 50 Hieracium s.str. taxa (Asteraceae) sampled across Europe.

They found that diploid taxa produced their seeds solely after double fertilization, i.e. sexually, whereas polyploid taxa reproduced strictly apomictically. However, very rare sexual reproduction was also recorded in certain polyploids. This is the first evidence of functional sexuality in polyploid members of the genus. While strict apomixis can enhance colonization abilities through increased reproductive assurance, residual sexuality increases genetic variation in otherwise asexual polyploids.