XVI International Botanical Congess

We examined whether differences in germination behavior between selfing and outcrossing variants, unrelated to the mating system, could explain the evolution of a discrete floral polymorphism in Senecio vulgaris (Asteraceae). We found that germination behaviour interacts with dispersal time and has a large effect on the relative fitness of these two morphs. Fitness differences between morphs were reversed depending on dispersal time. Both forms differ in their pattern of germination in relation to dispersal time and show opposite patterns of survival during winter and fecundity in relation to germination time. This demonstrates that the association between morph type and germination behaviour in S. vulgaris is of critical importance to the evolution of the polymorphism for outcrossing rate in the species.