, Volume 126, Issue 1, pp 76–83

Experimental manipulation of plant density and its effect on pollination and reproduction of two confamilial montane herbs

  • Maria Bosch
  • Nickolas M. Waser

DOI: 10.1007/s004420000488

Cite this article as:
Bosch, M. & Waser, N. Oecologia (2001) 126: 76. doi:10.1007/s004420000488


The density of a plant population is expected to influence reproductive success through changes in the quantity and quality of pollination service, or because both density and reproduction respond to quality of the local environment. We reported previously that seed set in sparse natural populations of Delphinium nuttallianum and Aconitum columbianum was lower than in nearby dense populations, whereas quantity of pollination service was equivalent. To explore the hypotheses that environmental quality or pollination quality are lower in sparse natural populations, leading to lower seed set, we manipulated density using arrays of potted plants. In three replicate experiments with D. nuttallianum, pollinator visitation rate and seed set were indistinguishable in sparse and dense arrays, consistent with the interpretation that environmental quality contributed to the earlier result in natural populations of this species. In three replicates with A. columbianum, visitation rate tended to increase with density, and seed set increased significantly, in contrast to our earlier result. One element of pollination quality, the degree of within-plant selfing, did not vary between sparse and dense arrays. These results highlight the complexity of mechanisms by which population parameters may influence plant reproductive success, and the temporal variation that characterizes pollination service.

Bumblebee Hummingbird Pollinator behavior Plant population density 

Copyright information

© Springer-Verlag 2000

Authors and Affiliations

  • Maria Bosch
    • 1
  • Nickolas M. Waser
    • 1
  1. 1.Department of Biology, University of California, Riverside, CA 92521, USA
  2. 2.Rocky Mountain Biological Laboratory, Crested Butte, CO 81224, USA
  3. 3.Present address: Laboratori de Botànica, Facultat de Farmàcia, Universitat de Barcelona, 08028 Barcelona, Spain