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Change of floral orientation affects pollinator diversity and their relative importance in an alpine plant with generalized pollination system, Geranium refractum (Geraniaceae)

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Abstract

Floral orientation may affect pollinator attraction and pollination effectiveness, and its influences may differ among pollinator species. We, therefore, hypothesized that, for plant species with a generalized pollination system, changes in floral orientation would affect the composition of pollinators and their relative contribution to pollination. Geranium refractum, an alpine plant with downward floral orientation was used in this study. We created upward-facing flowers by altering the flower angle. We compared the pollinator diversity, pollination effectiveness, and pollinator importance, as well as female reproductive success between flowers with downward- and upward-facing orientation. Results indicated that the upward-facing flowers were visited by a wider spectrum of pollinators (classified into functional groups), with higher pollinator diversity than natural flowers. Moreover, due to influences on visitation number and pollen removal, the pollinator importance exhibited by the main pollinator groups differed between flower types. Compared with natural flowers, the pollination contribution of principal pollinators (i.e., bumblebees) decreased in upward-facing flowers and other infrequent pollinators, such as solitary bees and muscoid flies, removed more pollen. Consequently, stigmatic pollen loads were lower in upward- than in downward-facing flowers. These findings reveal that floral orientation may affect the level of generalization of a pollination system and the relative importance of diverse pollinators. In this species, the natural downward-facing floral orientation may increase pollen transfer by effective pollinators and reduce interference by inferior pollinators.

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Acknowledgments

We thank two anonymous reviewers for their detailed and constructive comments, Xue-Gang Zhu and Shuang Tie for their help in field work, Xiao-Xia Li, Kuo Liao and Charles B. Fenster for the helpful comments and suggestions. This study was supported by grants from the National Natural Science Foundation of China (31170214 to YHG and 31070206 to CFY).

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Authors and Affiliations

  1. Laboratory of Plant Systematics and Evolutionary Biology, College of Life Sciences, Wuhan University, Wuhan, 430072, China

    Hui Wang, Chang-Long Xiao, Zheng Xiong, Dan Yu & You-Hao Guo

  2. Sino-African Biodiversity Resource Conservation Centre, Jomo Kenyatta University of Agriculture and Technology, P. O. Box 62000-00200, Nairobi, Kenya

    Robert W. Gituru

  3. Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, 430074, China

    Chun-Feng Yang

Authors
  1. Hui Wang
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  2. Chang-Long Xiao
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  3. Robert W. Gituru
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  4. Zheng Xiong
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  5. Dan Yu
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  6. You-Hao Guo
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  7. Chun-Feng Yang
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Correspondence to You-Hao Guo or Chun-Feng Yang.

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Communicated by M. Lawes.

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Wang, H., Xiao, CL., Gituru, R.W. et al. Change of floral orientation affects pollinator diversity and their relative importance in an alpine plant with generalized pollination system, Geranium refractum (Geraniaceae). Plant Ecol 215, 1211–1219 (2014). https://doi.org/10.1007/s11258-014-0379-y

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  • DOI: https://doi.org/10.1007/s11258-014-0379-y

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