The Nature of Selection on Flowering Time: Integrating Fitness Contributions through Male and Female Function

A central goal of evolutionary biology is to identify traits under selection and the causal mechanisms linking these traits to fitness. Most work towards this goal in plant systems has addressed the female component of fitness only. This thesis investigates the nature of selection on the timing of flowering onset - a trait of practical and theoretical importance - with equal emphasis on female and male function. The potential male fitness effects are many. First, flowering time may directly (or indirectly through correlation with another trait) influence ability to sire seed (e.g. by affecting pollen quantity). Second, because plants tend to mate assortatively by flowering time, an individual's flowering time might covary with the quality of dam it pollinates. Third, because flowering time partly determines the specific date range over which an individual reproduces, it may covary with exposure to pollinators, herbivores, abiotic stress, and other environmental characteristics that could affect fitness. I investigated these hypotheses through numerical modeling and experiments with the annual plantPh.D