Evolution of flowering time due to variation in the onset of pollen dispersal among individuals.

Abstract

The evolution of flowering time is often attributed to variations in pollinator rates over time. This study proposes that flowering time can evolve through siring success variation among individuals caused by differential pollen dispersal timing (a result of flowering time variation). By building quantitative genetic models, I show that flowering time evolves to be earlier when the pollen removal rate is low and pollen deposition rate is high, and the fertilization ability of removed pollen declines slowly. Using evolutionary game theory, I show that the evolutionarily stable variance of flowering time is large when the pollen removal rate is either low or high, the pollen deposition rate is moderate, and the fertilization ability of removed pollen declines rapidly. Investigation of the coevolution of flower longevity and flowering time shows that under constant pollination rates, late flowering will be correlated with long-lived flowers due to nonrandom mating, which suggests that the observed correlation between late flowering and short-lived flowers is caused by other factors, such as declining pollination rates during late-stage flowering. I discuss how altered pollination rates under climate change will influence flowering time evolution and the importance of distinguishing between pollen removal and deposition rates.