OVULE PACKAGING IN STOCHASTIC POLLINATION AND FERTILIZATION ENVIRONMENTS

The modular morphology of plants has important consequences for reprod uctive strategies. Ovules are packaged in discrete structures (flowers ) that usually vary stochastically in pollen capture and ovule fertili zation, because of the vagaries of pollen transfer by external agents. Different ovule packaging schemes may use limited reproductive resour ces more or less effectively, so that some number of ovules per flower may be optimal, given the prevailing probabilities of ovule fertiliza tion. I derive a phenotypic model for ovule number per flower that max imizes the expected total ovule fertilizations on a plant when pollina tion and fertilization vary randomly among individual flowers. This mo del predicts that, except for small or inexpensive flowers, ovules sho uld be ''oversupplied'' relative to the mean receipt of pollen tubes, so that pollen limitation of seed set should be common. Published data are congruent with this prediction. Additional hypotheses on the rela tion of ovule packaging to floral cost, plant size, and variance in po llen receipt are suggested by the model, but few data exist to evaluat e these hypotheses.