Selection by pollinators on the speciation of flowering plants

通过一系列实验研究了传粉昆虫对风铃草花朵大小的选择性。我从本州和伊豆群岛收集了风铃草的植物，并创造了一个花朵大小差异很大的风铃草实验种群。第一个实验是向传粉者赠送变异较大的花朵，并调查它们的反应。不同的传粉者(熊蜂、巨蜂、粉蜂)的反应是不同的。下一步的实验是将大小不等的雄花和大的雌花呈现给熊蜂，并研究雄花大小与雄花繁殖成功的关系。结果表明，较大的开花植株比较小的开花植株有更多的父本。第三个实验是利用干燥的熊蜂标本和新鲜的风铃花来调查熊蜂体内的花粉数量和位置。花的大小决定了花粉附着在熊蜂上的位置，其中较大的花比较小的花更适合花粉沉积，这表明风铃花的花大小是通过对熊蜂传粉者的形态适应来稳定的。

A series of experiments to investigate the selective forces by pollinating insects on the flower size of Campanula (Campanulaceae) were carried out. I collected plants of Campanula from Honshu and the Izu Islands, and created an experimental population of Campanula with a large variation in flower size. First experiment was to present flowers with large variation to pollinators and to investigate their responces. The responces of pollinators (bumblebees, megachilid bees, halictid bees) was different from each other.Next experiment was to present flowers of male-phased flower with size variation and large female-phased flower to bumblebees and to investigate the male reproductive success in relation to male flower size. It was found that larger flowered-plants more sired than smaller flowered-ones.Third experiment was to investigate the amount and position of pollen grains to bumblebee body, using dried bumblebee specimens and fresh Campanula flowers. It was found that flower size determined the position of pollaen attached to bumblebees in which larger flowers were more appropriate to pollen deposition than smaller ones.It was suggested that flower size of Campanula is stabilized by the selection through morphological adaptation to bumblebee pollinators.