Transition from wind pollination to insect pollination in sedges: experimental evidence and functional traits

Authors

  • Peter D. Wragg,

    1. School of Biological and Conservation Sciences, University of KwaZulu-Natal, Private Bag X01, Scottsville 3209, South Africa
    2. Present address: Department of Ecology, Evolution, and Behavior, University of Minnesota, 100 Ecology Building, 1987 Upper Buford Circle, St. Paul, MN 55108, USA
    Search for more papers by this author
  • Steven D. Johnson

    1. School of Biological and Conservation Sciences, University of KwaZulu-Natal, Private Bag X01, Scottsville 3209, South Africa
    Search for more papers by this author

Author for correspondence:
Peter D. Wragg
Tel: +1 651 315 2693
Email: wragg@umn.edu

Summary

  • Transitions from wind pollination to insect pollination were pivotal to the radiation of land plants, yet only a handful are known and the trait shifts required are poorly understood. We tested the hypothesis that a transition to insect pollination took place in the ancestrally wind-pollinated sedges (Cyperaceae) and that floral traits modified during this transition have functional significance.
  • We paired putatively insect-pollinated Cyperus obtusiflorus and Cyperus sphaerocephalus with related, co-flowering, co-occurring wind-pollinated species, and compared pairs in terms of pollination mode and functional roles of floral traits.
  • Experimentally excluding insects reduced seed set by 56–89% in putatively insect-pollinated species but not in intermingled wind-pollinated species. The pollen of putatively insect-pollinated species was less motile in a wind tunnel than that of wind-pollinated species. Bees, beetles and flies preferred inflorescences, and color-matched white or yellow models, of putatively insect-pollinated species over inflorescences, or color-matched brown models, of wind-pollinated species. Floral scents of putatively insect-pollinated species were chemically consistent with those of other insect-pollinated plants, and attracted pollinators; wind-pollinated species were unscented.
  • These results show that a transition from wind pollination to insect pollination occurred in sedges and shed new light on the function of traits involved in this important transition.

Ancillary