Size-Dependency of Sex-Allocation in Hermaphroditic, Monocarpic Plants

In the majority of monocarpic plant species there is an increase with plant size in the ratio of allocation of female function (seeds) to male function (flowers or pollen). A graphical model is presented that develops the general hypothesis that this may be due to fitness returns from the male function decreasing faster with increasing size than the returns from expenditure on the female function. Model and data are discussed with reference to the evolutionarily stable strategy-approach (E.S.S.) of Lloyd a Bawa (1984).