Selection by pollinators on the speciation of flowering plants

通过一系列实验研究了传粉昆虫对铃兰花大小的选择力。我从本州和伊豆群岛收集了风铃属植物，并创造了一个花大小变化很大的风铃属实验种群。第一个实验是将大变异的花朵呈现给传粉者，并调查它们的反应。传粉者（大黄蜂、巨型蜂、海蜂）的反应各不相同。接下来的实验是将大小变化的雄相花和大的雌相花呈现给大黄蜂，研究雄花大小与雄花繁殖成功率的关系。结果发现，大花植物比小花植物更易繁殖。实验三是利用干燥的大黄蜂标本和新鲜的风铃花，研究花粉粒在大黄蜂体内的数量和位置。发现花的大小决定了花粉附着在大黄蜂身上的位置，大花比小花更适合花粉沉积。结果表明，风铃花的大小是通过对大黄蜂传粉者的形态适应选择而稳定的。

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.