The importance of flower-pollinator interactions for reproductive isolation and speciation processes in the genus Salvia: an experimental approach

• Applicant: Professor Dr. Thomas Speck
• Subject Area: Evolution and Systematics of Plants and Fungi
• Term: from 2002 to 2008
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 5363671

The genus Salvia (sage) is characterised by the well-known `staminal lever mechanism'. Biomechanical methods and quantitative analyses of the functional morphology are used to test the functioning of the staminal levers and their importance for reproductive isolation among sympatric Salvia species or speciation and radiation processes in the genus, respectively. (1) In the first set of experiments, we tested if the forces and energies required to release the staminal levers are relevant for the foraging behaviour of the pollinators. For this purpose, the insects were trained to an 'artificial flower', and the forces which are exerted by the insects to get to the food source were determined. These forces were then compared to the forces necessary for the movement of the staminal levers and for the deformation of flowers in Salvia, measured with a highsensitive force test gauge. Our findings show that the staminal levers are evolved for an ease of triggering, and that the forces necessary to release the stamin al levers are irrelevant for the visiting insects. (2) In a second set of experiments, the hypothesis is tested that the staminal lever mechanism represents a key function in stabilising sympatric Salvia species via accurate and species-specific transfer of pollen on pre-defined regions of the pollinators. We study experimentally if the process of pollen deposition on different species of pollinators is accurate enough to prevent or minimise the transfer of pollen on the stigma of other sympatric Salvia species.

• DFG Programme: Priority Programmes
• Subproject of: SPP 1127: Radiations - Origins of Biological Diversity