The Role of Polyploidy in the Evolution of Gender Dimorphism: An Experimental Approach using Fragaria vesca

The Role of Polyploidy in the Evolution of Gender Dimorphism: An Experimental Approach Using Fragaria vesca Allison Kwok Advisor: University of Guelph, 2013 Dr. Brian C Husband The evolution of gender dimorphism is associated with the incidence of polyploidy in several plant taxa, but the underlying causes of this relationship are not well understood. Here I investigate the direct and indirect effects of polyploidy on gender dimorphism in Fragaria vesca by synthesizing neotetraploids and comparing them to diploids with respect to vegetative, gender and mating system traits. Neotetraploids were induced by treating diploids with colchicine; comparisons between colchicine-treated diploids (unconverted) and untreated diploids indicate that colchicine has no secondary effects. In the greenhouse, diploids were 38% larger than neotetraploids. Neotetraploids produced fewer pollen grains and ovules, and relative investment in male reproduction was 70% less than diploids. In pollinator-exclusion experiments, diploids autonomously produced 36% greater fruit set and 69% greater seed set than neotetraploids. Neotetraploids had 22% lower seed set in open-pollinated experimental populations. Based on seed set from hand pollinations, diploids and neotetraploids did not differ in selfing rate or early acting inbreeding depression. These data suggest that polyploidy can cause an instantaneous change in gender expression, thereby providing the raw material for gender dimorphism. Indirect effects of polyploidy, through increases in selfing, are not supported.