Evolutionarily Stable Reproductive Strategies in Sexual Organisms: III. The Effects of Lottery Density Dependence and Pollen Limitation

This paper extends our previous work on modelling, within a single framework, the allocation of resources to reproduction vs. survival and the male vs. female components of reproduction in perennial plants. We derive the evolutionarily stable strategy (ESS) results under pollen limitation for both hermaphroditic and dioecious plant populations held stable through density-dependent juvenile recruitment. Pollen limitation affects female reproductive allocation in our model because there is post-flowering provisioning of offspring. We find that pollen limitation is unimportant to the ESS reproductive allocation and sex allocation so long as there are enough seeds to fill the empty sites left by the death of adults. To the extent that the relationships between gamete output and resource investment are linear for both sexes or sex functions, the separate treatment of reproductive and sex allocation in modern life-history and sex-allocation theories is adequate. In such cases, the ESS sex allocation is exactly what is found in traditional sex allocation theory, and the ESS reproductive allocation of hermaphrodites or females in a dioecious species maximizes the amount of resources allocated to reproduction during an average lifespan, an analogue of the usual maximization principle in life-history theory modified to include the possibility of pollen limitation and extended seed maturation. The ESS reproductive allocation of males in a dioecious species maximizes lifetime pollen production, independent of pollen limitation and the femaleʹs resource allocation.