Floral Anthesis Rate and Pollen Limitation in Delphinium glaucum and their Consequences for Female Fitness

Abstract

Phenological mismatch between plants and their pollinators and/or interspecific competition for pollination can cause insufficient pollen quantity and/or inadequate pollen quality to limit seed production and siring. Inflorescence display size, a dynamic part of pollinator attraction, influences pollinator behaviour and movement. Thus, a rapid increase in display size as plants begin flowering caused by initially rapid flower anthesis should promote recruitment of pollinators to newly flowering individuals and species. Tests of two assumptions of this hypothesis for Delphinium glaucum revealed: 1) declining anthesis rate during a plant’s flowering period is an intrinsic characteristic of inflorescence architecture, rather than a response to internal resource economy; and 2) pollinator limitation early during the flowering period reduced ovule fertilization and elevated autogamous self-mating. These results suggest that rapidly increasing initial display size largely contributed to the quality, rather than the quantity of female mating. Consequences for male outcross success remain to be assessed.