The consequences of inflorescence architecture for bumble bee behaviour and plant mating

Angiosperm floral displays vary greatly in size, flower design, and flower arrangement (inflorescence architecture), presumably reflecting adaptation to different pollination environments. However, the functional significance of inflorescence architecture remains poorly understood. An experiment that examined the foraging of three species of bumble bees on three types of artificial inflorescences revealed that architecture manipulates bee behaviour through weak influences on the number of flowers visited and strong effects on the consistency of foraging paths among flowers. A model simulating pollination with the observed bee behaviour assessed the influence of architecture on several mating parameters. The weak effect of architecture on the number of flowers visited yielded small, but significant, effects on mating when all flowers were simultaneously hermaphroditic. In contrast, the influence of architecture on foraging consistency greatly influenced mating when inflorescences segregated sex functions. These effects bear diverse consequences for the evolution of inflorescence architecture, flower design and plant mating.