CONSEQUENCES OF MALE-STERILITY IN PHACELIA-DUBIA

In field studies, females of the gynodioecious Phacelia dubia had an e qual or lower fecundity than hermaphrodites. Females had a lower fruit set and the probability of fruit production per plant decreased in th e year with higher abundance of floral resources. Additionally, the na tural progenies of females were less viable and had lower seed weights than those of hermaphrodites. In controlled pollinations, however, fe males had higher fruit set and seed production per fruit than hermaphr odites, but this was also dependent on the degree of relatedness of th e pollen donor. Inbreeding depression in fruit set and seed production per fruit was higher in females than in hermaphrodites. These results suggest that genetic and ecological factors influence the relative fe male to hermaphrodite fecundity. The year to year variation in frequen cy of male sterility detected in the field cannot be solely explained by the relative performance of the sexes and their progenies. Instead, other factors such as nucleo-cytoplasmic interactions are probably mo re important in the dynamics of gynodioecy in P. dubia.