, Volume 136, Issue 3, pp 394–401 | Cite as

Flowering phenology and compensation for herbivory in Ipomopsis aggregata

  • Rachael S. Freeman
  • Alison K. Brody
  • Christopher D. Neefus
Plant Animal Interactions


The mechanisms and circumstances that affect a plant's ability to tolerate herbivory are subjects of ongoing interest and investigation. Phenological differences, and the timing of flowering with respect to pollinators and pre-dispersal seed predators, may provide one mechanism underlying variable responses of plants to herbivore damage. The subalpine wildflower, Ipomopsis aggregata, grows across a wide range of elevations and, because phenology varies with elevation, phenological delays associated with elevation may affect the ability of I. aggregata to compensate for or tolerate browsing. Thus, we examined the response of I. aggregata to herbivory across an elevation gradient and addressed the interactions among phenological delays imposed by damage, elevation, pre-dispersal seed predation and pollination, on I. aggregata's compensatory response. Among high and low elevation populations in areas near the Rocky Mountain Biological Laboratory (RMBL) in Gothic, Colorado, we compared the responses of naturally browsed, artificially browsed (clipped), and unbrowsed (control) plants of I. aggregata. We compared responses in the date of initiation of flowering, timing of peak bloom, floral display, nectar production and sugar concentration, oviposition and fruit destruction by the pre-dispersal seed predator Hylemya sp. (Anthomyiidae), fruit production, and aboveground biomass production. Clipping had the greatest effect on reproductive success and clipped plants at high elevation exhibited the lowest tolerance for herbivory. The effects of browsing appear to be mediated by flowering phenology, and both browsing and elevation delayed flowering phenology. Time needed for regrowth delays flowering, and thus affects the overlap with seed predators and pollinators. As a result of delayed flowering, naturally browsed and clipped plants incurred lower rates of seed predation. In the absence of seed predation, plants would exhibit a lower tolerance to herbivory since naturally and artificially browsed plants had fewer fruits destroyed by Hylemya larvae. We provide additional evidence that, for populations near the RMBL, clipping and natural browsing do not have the same effect on I. aggregata plants. This may be due to the selection of larger plants by herbivores. Although under some conditions plants may tolerate browsing, in areas where the growing season is short a phenological delay imposed by damage is likely to significantly reduce plant fitness. Identifying the mechanisms that allow plants to tolerate herbivore damage will help to develop a general framework for understanding the role of tolerance in plant population and community dynamics, as well as plant-herbivore interactions.


Compensation Tolerance Herbivory Elevation Phenology 



We thank Mary Price for statistical advice and Shelley Higgins and Holly Prendeville for assistance in the field. We are also grateful to Tom Lee, Kurt May and two anonymous reviewers for insightful and thoughtful comments on previous versions of the manuscript. Our work was supported by the Department of Plant Biology and Graduate School at the University of New Hampshire, Durham and by NSF grant DEB-9806501 to A.K.B. We also thank the Rocky Mountain Biological Laboratory and its staff for providing facilities and support.


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Copyright information

© Springer-Verlag 2003

Authors and Affiliations

  • Rachael S. Freeman
    • 1
    • 2
    • 4
  • Alison K. Brody
    • 2
    • 3
  • Christopher D. Neefus
    • 1
  1. 1.Department of Plant BiologyUniversity of New HampshireDurhamUSA
  2. 2.Rocky Mountain Biological LaboratoryCrested ButteUSA
  3. 3.Department of BiologyUniversity of VermontBurlingtonUSA
  4. 4.30 Hulbert AveNantucketUSA

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