Oecologia

, Volume 173, Issue 3, pp 1023–1032

Trait-mediated indirect effects, predators, and disease: test of a size-based model

  • Christopher R. Bertram
  • Mark Pinkowski
  • Spencer R. Hall
  • Meghan A. Duffy
  • Carla E. Cáceres
Community ecology - Original research

DOI: 10.1007/s00442-013-2673-0

Cite this article as:
Bertram, C.R., Pinkowski, M., Hall, S.R. et al. Oecologia (2013) 173: 1023. doi:10.1007/s00442-013-2673-0

Abstract

Increasing prevalence of wildlife disease accentuates the need to uncover drivers of epidemics. Predators can directly influence disease prevalence via density-mediated effects (e.g., culling infected hosts leading to reduced disease prevalence). However, trait-mediated indirect effects (TMIEs) of predators can also strongly influence disease—but predicting a priori whether TMIEs should increase or decrease disease prevalence can be challenging, especially since a single predator may elicit responses that have opposing effects on disease prevalence. Here, we pair laboratory experiments with a mechanistic, size-based model of TMIEs in a zooplankton host, fungal parasite, multiple predator system. Kairomones can either increase or decrease body size of the host Daphnia, depending on the predator. These changes in size could influence key traits of fungal disease, since infection risk and spore yield increase with body size. For six host genotypes, we measured five traits that determine an index of disease spread (R0). Although host size and disease traits did not respond to kairomones produced by the invertebrate predator Chaoborus, cues from fish reduced body size and birth rate of uninfected hosts and spore yield from infected hosts. These results support the size model for fish; the birth and spore yield responses should depress disease spread. However, infection risk did not decrease with fish kairomones, thus contradicting predictions of the size model. Exposure to kairomones increased per spore susceptibility of hosts, countering size-driven decreases in exposure to spores. Consequently, synthesizing among the relevant traits, there was no net effect of fish kairomones on the R0 metric. This result accentuates the need to integrate the TMIE-based response to predators among all key traits involved in disease spread.

Keywords

DaphniaMetschnikowiaChaoborusHostParasite

Supplementary material

442_2013_2673_MOESM1_ESM.doc (186 kb)
Supplementary material 1 (DOC 186 kb)

Copyright information

© Springer-Verlag Berlin Heidelberg 2013

Authors and Affiliations

  • Christopher R. Bertram
    • 1
    • 2
  • Mark Pinkowski
    • 2
  • Spencer R. Hall
    • 3
  • Meghan A. Duffy
    • 4
  • Carla E. Cáceres
    • 1
    • 2
  1. 1.Program in Ecology, Evolution and Conservation BiologyUniversity of Illinois at Urbana-ChampaignUrbanaUSA
  2. 2.School of Integrative BiologyUniversity of Illinois at Urbana-ChampaignUrbanaUSA
  3. 3.Department of BiologyIndiana UniversityBloomingtonUSA
  4. 4.Department of Ecology and Evolutionary BiologyUniversity of MichiganAnn ArborUSA