Reproductive Effort in Annual and Perennial Species of Plantago (Plantaginaceae)

Abstract

Annual species of Plantago (Plantaginaceae) have higher reproductive efforts and seed and fruit outputs per unit leaf area than perennial species, as determined by using both field collected samples and herbarium material. Further, spring annuals have higher reproductive efforts than summer annuals, and weedy perennials have higher reproductive efforts than nonweedy perennials. While virtually every individual in the populations of the annual species was flowering, many or often most of the plants in the perennial populations were not flowering. The ability of the perennial species to defer flowering is related to their generally larger leaf area. The agreement of these patterns of variation in reproductive effort and timing of reproduction with the theoretical predictions constitute an argument for the adaptive nature of this variation.