XVI International Botanical Congess

The evolution of dioecy via gynodioecy has been well-characterized in plants, yet few opportunities exist to study this process within a single species. Wurmbea dioica is comprised of populations that are either monomorphic for gender, containing only cosexuals, or dimorphic for gender, containing separate sexes. We investigated ecological factors associated with gender variation in W. dioica in W. Australia. In sympatry, dimorphic populations occurred in drier microsites that monomorphic populations. Males and females allocated significantly more biomass to below-ground structures than cosexuals, and were less water use efficient despite lower water availability. Cosexuals produced larger flowers with more pollen and ovules than unisexuals. Differences in pollinator service, resource, availability and allocation have likely played a role in the evolution of gender variation in W. Dioica. & S.C.H. BarrettUniv. of Toronto,Canada