Rethinking pathways to the dioecy-polyploidy association: Genera with many dioecious species have fewer polyploids.

Area of Science:

• Evolutionary biology
• Plant reproductive strategies

Background:

• A positive association between dioecy and polyploidy is frequently observed.
• Dioecious species cannot self-reproduce, creating a theoretical conflict with polyploid establishment, which often benefits from self-reproduction.

Purpose of the Study:

• To resolve the theoretical conflict between dioecy and polyploidy.
• To test the hypothesis that the inability of dioecious species to self-reproduce hinders polyploid establishment.
• To investigate the association between polyploidy and dioecy across genera and species.

Main Methods:

• Utilized three public databases to gather ploidy and sexual system data for 131 genera and 546 species.
• Quantified the relationship between polyploid and dioecious species frequencies across genera.
• Analyzed the proportion of polyploids with hermaphroditism and dioecy across species, controlling for phylogenetic history.

Main Results:

• A negative association was found between the proportion of polyploids and dioecious species across genera, consistent across clades.
• The sexual system of species was not significantly associated with polyploidy when analyzed at the species level.

Conclusions:

• Polyploids are infrequent in genera dominated by dioecious species, supporting the theory that self-reproduction is crucial for polyploid establishment.
• The low frequency of polyploidy in dioecious species suggests the positive association is not as pervasive as previously thought.
• Findings align with previous research if polyploidy drives transitions to dioecy, rather than the reverse.