Larsson Magnus
Department of Plant Ecology, Evolutionary Biology Centre, Uppsala University, Villavägen 14, 75236 Uppsala, Sweden.
Oecologia. 2005 Dec;146(3):394-403. doi: 10.1007/s00442-005-0217-y. Epub 2005 Oct 27.
A critical issue in pollination ecology is the evolution of generalist pollination systems, and under which conditions floral specializations evolve from these. The gynodioecious herb Knautia arvensis (Dipsacaceae) exhibits a generalized pollination system, but is visited by both generalist and specialist flower-visitors. The present study tested pollinator effectiveness and pollinator importance of the pollen specialist solitary bee Andrena hattorfiana (Andrenidae) vs. the generalist flower-visitors to K. arvensis on the island of Oland, SE Sweden. Females of the specialist bee removed more pollen per inflorescence-visit than the major groups of generalist visitors such as bumblebees and flies. They also deposited more pollen per inflorescence-visit than any of the generalist visitor groups. The females have a preference for pollen-presenting vs. stigma-presenting inflorescences, a pattern shared with most of the generalist flower-visitors. Females of the specialist exert such a strong preference that they, despite their great pollinator effectiveness, make modest contribution to pollen transfer in K. arvensis. The females of A. hattorfiana accounted for 14.2% of the overall visits and 5.8% of the total pollination, the rest being performed by generalist visitors and males of A. hattorfiana. This study shows that pollinator effectiveness of a specialist can be superior while generalist flower-visitors select floral characters towards generalization through their greater contribution to overall pollen flow.
传粉生态学中的一个关键问题是泛化传粉系统的进化，以及在何种条件下花的特化从这些系统中演变而来。雌雄异株草本植物田野山萝卜（川续断科）表现出一种泛化传粉系统，但会受到泛化和特化的访花者的光顾。本研究在瑞典东南部的厄兰岛上，测试了花粉特化的独居蜜蜂哈托夫安德rena（地蜂科）与田野山萝卜的泛化访花者相比的传粉者效率和传粉者重要性。特化蜜蜂的雌蜂每次访花从每个花序上采集的花粉比主要的泛化访花者群体（如大黄蜂和苍蝇）更多。它们每次访花在每个花序上沉积的花粉也比任何泛化访花者群体都多。雌蜂偏好有花粉的花序而非有柱头的花序，这一模式与大多数泛化访花者相同。特化蜜蜂的雌蜂表现出如此强烈的偏好，以至于尽管它们传粉效率很高，但对田野山萝卜的花粉传播贡献不大。哈托夫安德rena的雌蜂占总访花次数的14.2%，占总传粉量的5.8%，其余传粉由泛化访花者和哈托夫安德rena的雄蜂完成。这项研究表明，特化传粉者的传粉效率可能更高，而泛化访花者通过对总体花粉流动的更大贡献，选择了趋向泛化的花部特征。
