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

鼠尾草属(鼠尾草)的特点是众所周知的“雄蕊杠杆机制”。用生物力学方法和功能形态的定量分析方法，分别测试了雄蕊杠杆的功能及其对共域丹参属物种间生殖隔离或物种形成和辐射过程的重要性。(1)在第一组实验中，我们测试了释放雄蕊杠杆所需的力和能量是否与传粉者的觅食行为有关。为此，这些昆虫被训练成一种“人造花”，并确定了昆虫到达食物来源所施加的力量。然后将这些力与雄蕊杠杆移动和丹参花朵变形所需的力进行比较，并用高灵敏度的力测试仪进行测量。我们的发现表明，雄蕊杠杆的进化是为了更容易触发，而释放雄蕊杠杆所需的力量与来访的昆虫无关。(2)在第二组实验中，验证了这一假说，即雄蕊杠杆机制通过在授粉者预定义的区域上准确且特定于物种的花粉转移，在稳定共生的丹参物种方面起着关键作用。我们通过实验研究了不同种类的传粉者的花粉沉积过程是否足够准确，以防止或最大限度地减少其他共生的丹参物种柱头上的花粉转移。

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.