Selection on floral design in Polemonium brandegeei (Polemoniaceae): female and male fitness under hawkmoth pollination

Plant-pollinator interactions promote the evolution of floral traits that attract pollinators and facilitate efficient pollen transfer. The spatial separation of sex-organs, herkogamy, is believed to limit sexual interference in hermaphrodite flowers. Reverse herkogamy (stigma recessed below anthers) and long narrow corolla-tubes are expected to promote efficiency in male function under hawkmoth pollination. We tested this prediction by measuring selection in six experimental arrays of Polemonium brandegeei, a species that displays continuous variation in herkogamy, resulting in a range of recessed to exserted stigmas. Under glasshouse conditions, we measured pollen removal and deposition, and estimated selection gradients (ß) through female fitness (seeds set) and male fitness (siring success based on 6 polymorphic microsatellite loci). Siring success was higher in plants with more nectar sugar and narrow corolla-tubes. However, selection through female function for reverse herkogamy w...

植物-传粉者互作可推动吸引传粉者并促进高效花粉传递的花部性状演化。学界普遍认为，性器官的空间分离——雌雄异位（herkogamy）——能够限制两性花内的性干扰。反向雌雄异位（reverse herkogamy，即柱头凹陷于花药下方）与狭长花冠筒，被预期可在天蛾传粉条件下提升雄性功能的执行效率。我们通过测定布兰德花荵（Polemonium brandegeei）的6个实验种群的选择压力，验证了这一预测：该物种的雌雄异位存在连续变异，可产生从柱头凹陷到柱头伸出的一系列表型。在温室条件下，我们测定了花粉移除量与沉积量，并通过雌性适合度（结籽数）和雄性适合度（基于6个多态微卫星位点的父本成功率）估算了选择梯度（selection gradients，β）。花蜜糖含量更高、花冠筒更狭长的植株，其父本成功率也更高。然而，针对反向雌雄异位的雌性功能选择作用却……