Kobayashi Shiro, Inoue Ken, Kato Masahiro
Department of Biological Sciences, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113, Japan Fax: -(81)3-3818-5367; e-mail:
Biological Institute and Herbarium, Faculty of Science, Shinshu University, Matsumoto 390, Japan, , , , , , JP.
Oecologia. 1997 Aug;111(4):535-542. doi: 10.1007/s004420050268.
Flowers exhibiting a large corolla encompassing a wide inner space, characteristic of bee-pollinated plant species, are postulated to be maintained by a natural selection mechanism related to their pollinators. To confirm the existence and to elucidate the mechanism of such selection, we investigated the effect of floral traits on male reproductive success (RS) and its components in experimental populations of Campanula punctata and C. microdonta (Campanulaceae) under pollination by Bombus diversus (Apidae). Larger corolla width significantly increased male RS per fruit, though there was no effect on pollen removal, showing, for the first time, that a wide corolla serves a reproductive function of enhancing pollen transfer efficiency (ratio of male RS to pollen removal). Selection by pollen transfer efficiency through an indirect effect of initial pollen number or postpollination success was experimentally ruled out. Several mechanisms are proposed to explain how this selection factor is exerted on C. punctata corollas.
具有大花冠且内部空间宽阔的花朵，这是蜜蜂授粉植物物种的特征，据推测是通过与传粉者相关的自然选择机制得以维持。为了证实这种选择的存在并阐明其机制，我们在熊蜂（Apidae科）授粉的情况下，研究了花性状对桔梗（Campanula punctata）和小花桔梗（C. microdonta）（桔梗科）实验种群中雄性繁殖成功率（RS）及其组成部分的影响。花冠宽度较大显著提高了每个果实的雄性RS，尽管对花粉去除没有影响，这首次表明宽花冠具有提高花粉转移效率（雄性RS与花粉去除率之比）的繁殖功能。通过初始花粉数量或授粉后成功率的间接影响，由花粉转移效率进行的选择在实验中被排除。提出了几种机制来解释这种选择因素是如何作用于桔梗花冠的。
