Oecologia

, Volume 87, Issue 1, pp 43–50

Demographic costs of Chaoborus-induced defences in Daphnia pulex: a sensitivity analysis

  • Mari Walls
  • Hal Caswell
  • Matti Ketola
Original Papers

DOI: 10.1007/BF00323778

Cite this article as:
Walls, M., Caswell, H. & Ketola, M. Oecologia (1991) 87: 43. doi:10.1007/BF00323778
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Summary

We examined the demographic costs of Chaoborus-induced defensive spine structures in Daphnia pulex. Our aim was to assess the role of resource limitation and the interaction effects of limiting food level and antipredator structures on fitness of D. pulex and to pinpoint those life stages that are most sensitive to changes in the defence regime. Chaoborus-induced and typical morphotypes of D. pulex were reared at high and low food concentrations. Instar-based matrix population models were used to quantify the effects of predator-induction, food and their interaction on fitness of D. pulex. Predator-induction caused a statistically significant reduction in fitness at low food levels, but not at high food levels. Sensitivity analyses revealed that the fitness effects were primarily due to changes in the growth rate in instars 1–5, and secondarily to small reductions in the fertility of instars 5–10. The interaction between Chaoborus exposure and low food concentration was negative, and mediated through growth and fertility components. Both these components were reduced more in the Chaoborus-exposed, low food treatment than would be expected in the absence of interaction.

Key words

Predator-prey interactionInducible defencePopulation growthDaphnia pulexChaoborus

Copyright information

© Springer-Verlag 1991

Authors and Affiliations

  • Mari Walls
    • 1
  • Hal Caswell
    • 2
  • Matti Ketola
    • 1
  1. 1.Laboratory of Ecological Zoology, Department of BiologyUniversity of TurkuTurkuFinland
  2. 2.Biology DepartmentWoods Hole Oceanographic InstitutionWoods HoleUSA