Evolution of owering strategies in Oenothera glazioviana: an integral projection model approach

The timing of reproduction is a key determinant of Ž tness. Here, we develop parameterized integral projection models of size-related  owering for the monocarpic perennial Oenothera glazioviana and use these to predict the evolutionarily stable strategy (ESS) for  owering. For the most part there is excellent agreement between the model predictions and the results of quantitative Ž eld studies. However, the model predicts a much steeper relationship between plant size and the probability of  owering than observed in the Ž eld, indicating selection for a ‘threshold size’  owering function. Elasticity and sensitivity analysis of population growth rate l and net reproductive rate R0 are used to identify the critical traits that determine Ž tness and control the ESS for  owering. Using the Ž tted model we calculate the Ž tness landscape for invading genotypes and show that this is characterized by a ridge of approximately equal Ž tness. The implications of these results for the maintenance of genetic variation are discussed.