Intrapopulation Variation in Reproduction and Seed Mass of a Beach Annual; Cakile edentula var. lacustris

Abstract

A field study was conducted to examine phenotypic plasticity in reproduction and seed mass (weight per seed) variability of Cakile edentula var: lacustris (Brassicaceae). This beach annual exhibited large intrapopulation variation in plant size, seed production, and seed mass. The plants grew large in favourable microenvironments on the beach. For example, close to the lake the plants had significantly greater crown area and number of seeds per plant than those farther inland primarily due to hlgher soil moisture and nutrient content of occupied microsites. A large number of seeds within fruits were aborted but abortion was significantly higher (74%) in lower than upper fruits (14%), The coefficient of variation for mass per seed was 53% for upper seeds and 48.5% for lower seeds. Mean seed mass per plant decreased as the season progressed from July to September. The data suggest that C. edentula responds to unstable shoreline habitat by phenotypic plasticity in plant size, reproduction, and fruit abortion.