FITNESS CONSTRAINTS ON FLOWER NUMBER, SEED NUMBER AND SEED SIZE IN THE DIMORPHIC SPECIES PRIMULA-FARINOSA L AND ARMERIA-MARITIMA (MILLER) WILLD

Using two dimorphic species with diallelic incompatibility, Primula fa rinosa L. and Armeria maritima (Miller) Willd., we tested the hypothes is that an association of seedling performance with seed size, and an inverse association of seed size with seed number, might, contrary to most fitness models, select for plants which set relatively few seeds. In P. farinosa we discovered positive relationships between seed numb er per capsule and capsule number per inflorescence. As capsules are f ormed in most flowers, scapes with few flowers set the fewest seeds pe r capsule. This suggests that conspicuousness to pollinators and/or pl ant resource play an important role in reproductive success in this sp ecies. Seed size and seedling performance were also positively associa ted. For P. farinosa, which has multi-seeded fruits, we discovered an inverse association between seed size and seed number for capsules con taining more than 65 seeds. We suggest that stabilizing selection may occur for flower number per inflorescence in this species, as inflores cences with 8-11 capsules tend to set many seeds which may be ineffici ently small. This tends to confirm our hypothesis. However, for A. mar itima there is a positive association between seed size and seed numbe r per inflorescence. For such plants with single-seeded fruits there s hould be directional selection for large flower number per inflorescen ce, a trend which may have led to the evolution of the capitulum.