Splash-cups, springboards, and sink or swim – Preliminary study of the strategies for vegetative propagule dispersal in Pygmy Drosera

The Drosera of the subgenus Bryastrum, commonly referred to as pygmy sundews are unique to the genus in that all bar one produce vegetative clonal propagules known as gemmae. These gemmae are thought to be dispersed via a novel adaptation known as a splash-cup, but little is known about its effectiveness or other strategies employed by the plants. In this preliminary study, the splash-cup was tested and its effectiveness measured. The role of the stipules, which form the walls of the splash-cup were also examined along with other features of the plants’ architecture. The splash-cup was found to play a critical role in gemmae dispersal while the theory that the stipules perform as spring-loaded catapults was unsupported. Additionally, gemmae were found to either sink or float depending on the taxon. Observational evidence is provided which suggests the structure of a gemma plays a significant role in the success of each taxon in its preferred habitat.