Selection by pollinators on the speciation of flowering plants

本文研究了传粉昆虫对桔梗花大小的选择力。我从本州和伊豆群岛收集了风铃草属植物，并创建了一个花大小变化很大的风铃草实验种群。第一个实验是将变异较大的花呈现给传粉者，并调查它们的反应。不同的传粉者（熊蜂、大蜂、大叶蜂）的反应不同，本试验将不同大小的雄花和大雌花分别呈给熊蜂，研究雄花大小与雄花繁殖成功率的关系。实验三采用干燥的熊蜂标本和新鲜的风铃草花，研究熊蜂花粉粒在熊蜂体内的数量和位置。结果表明，风铃草花的大小决定了花粉在熊蜂上的附着位置，大花比小花更适合花粉的附着，这表明风铃草花的大小是通过对熊蜂传粉者的形态适应性选择而稳定下来的。

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.