FUNCTIONAL DIOECY AND ANDROMONOECY IN SOLANUM.

Area of Science:

• Evolutionary biology
• Plant reproductive strategies
• Angiosperm breeding systems

Background:

• The genus Solanum exhibits diverse breeding systems, including andromonoecy, androdioecy, and dioecy.
• Understanding the evolution of these systems is crucial for plant reproductive biology.

Purpose of the Study:

• To clarify the nature and evolutionary pathways of andromonoecy, androdioecy, and dioecy in Australian Solanum species.
• To investigate the functional significance of pollen dimorphism in reproductive strategies.

Main Methods:

• Field and laboratory studies of 19 diclinous Solanum species.
• Morphological analysis of floral structures and pollen types.
• Review of breeding systems in other angiosperm families.

Main Results:

• Ten species are andromonoecious, likely derived from hermaphroditic ancestors through flower modification.
• Nine species are functionally dioecious, exhibiting pollen dimorphism with non-viable pollen in pistillate flowers.
• No evidence for true androdioecy was found in Solanum or other angiosperms.

Conclusions:

• Andromonoecy and dioecy are polyphyletic in Solanum, with dioecy arising from both hermaphroditic and andromonoecious ancestors.
• Functionally dioecious Solanum species utilize inaperturate pollen as a pollinator reward in nectarless flowers.
• The study challenges the prevalence of androdioecy as a breeding system in angiosperms.