Functional implications of the specialized staminal appendages in alpine ginger (Roscoea spp.: Zingiberaceae).

Abstract

Floral organs are widely believed to enhance the pollination and reproductive success of angiosperms. However, the functional implication of some floral structures is still unknown. In this study, we explored the functional role of staminal appendages on male and female reproductive success of Himalayan Roscoea spp. and tested if their function differed between species with biotic pollination and autonomous selfing. Phenotypic manipulation is a powerful approach to test the functional effect of a particular trait on plant fitness. We compared various proxies of pollination success between intact flowers and flowers with manually excised staminal appendages. We found that the rate of visitation did not differ between intact and manipulated flowers. Our results revealed that in outcrossing Roscoea spp., the staminal appendages act as triggering devices to facilitate pollen release and deposition and also to manipulate the foraging position of pollinators to ensure both male and female reproductive success. In contrast, in autonomously selfing Roscoea spp., the removal of staminal appendages did not affect any aspect of pollination processes. Our results suggest that the staminal appendages are an integral component of outcrossing in Roscoea spp. and are maintained by selection pressure through both male and female reproductive success. This study provides important insights on how variation in breeding systems can provoke changes in the structure and function of floral organs among congeners.