Seed size and seed number tradeoffs in Banksia Geographic variation in life histories in Burchardia umbellata . Males with larger flowers achieve higher reproductive success than plants with smaller flowers, supporting the view that selection for larger flower size has occurred through male function rather than female function. The nitrogen and phosphorous content of seeds increases with seed size in Banksia marginata and B. spinulosa , and larger seeds produce larger seedlings than small seeds. Although stabilising selection should eliminate seed mass variation within plants, such variation persists because resource constraints limit the ability of plants to control individual seed size. The size and dynamics of the seed bank may limit recruitment in this species.
Seed set in many plant populations is pollen limited.
Quantifying the relative importance of pollen quantity and pollen quality in limiting seed set are necessary to understand the functional significance and evolution of floral traits. In Burchardia umbellata , genetically related pollen deposited on stigmas caused interference in the style and ovary, reducing fertilizations by cross pollen. Our study demonstrates adverse effects of interference under natural conditions, and indicates that inappropriate pollen deposition may contribute to pollen limitation more often than previously recognized. Vaughton, G. and Ramsey, M. 2001. Ramsey, M. and Vaughton, G. 2001.