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12 results

  • Parasitoid community responds indiscriminately to fluctuating spruce budworm (Lepidoptera: Tortricidae) and other caterpillars on balsam fir (Pinaceae)

  • Christopher J. Greyson-Gaito, Kevin S. McCann, Jochen Fründ, Christopher J. Lucarotti, M. Alex Smith, Eldon S. Eveleigh
  • Journal:
    The Canadian Entomologist / Volume 153 / Issue 4 / August 2021
    Published online by Cambridge University Press:
    22 April 2021, pp. 482-496
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  • The world is astoundingly variable, and organisms – from individuals to whole communities – must respond to variability to survive. One example of nature’s variability is the fluctuations in populations of spruce budworm, Choristoneura fumiferana Clemens (Lepidoptera: Tortricidae), which cycle every 35 years. In this study, we examined how a parasitoid community altered its parasitism of budworm and other caterpillar species in response to these fluctuations. Budworm and other caterpillar species were sampled from balsam fir (Pinaceae) in three plots for 14 years in Atlantic Canada, then were reared to identify any emerging parasitoids. We found that the parasitoid community generally showed an indiscriminate response (i.e., no preference, where frequencies dictated parasitism rates) to changes in budworm frequencies relative to other caterpillar species on balsam fir. We also observed changes in topology and distributions of interaction strengths between the parasitoids, budworm, and other caterpillar species as budworm frequencies fluctuated. Our study contributes to the hypothesis that hardwood trees are a critical part of the budworm–parasitoid food web, where parasitoids attack other caterpillar species on hardwood trees when budworm populations are low. Taken together, our results show that a parasitoid community collectively alters species interactions in response to variable budworm frequencies, thereby fundamentally shifting food-web pathways.

Adaptive Food Webs
  • Stability and Transitions of Real and Model Ecosystems
  • Edited by John C. Moore, Peter C. de Ruiter, Kevin S. McCann, Volkmar Wolters
  • Published online:
    05 December 2017
    Print publication:
    21 December 2017
  • Presenting new approaches to studying food webs, this book uses practical management and policy examples to demonstrate the theory behind ecosystem management decisions and the broader issue of sustainability. All the information that readers need to use food web analyses as a tool for understanding and quantifying transition processes is provided. Advancing the idea of food webs as complex adaptive systems, readers are challenged to rethink how changes in environmental conditions affect these systems. Beginning with the current state of thinking about community organisation, complexity and stability, the book moves on to focus on the traits of organisms, the adaptive nature of communities and their impacts on ecosystem function. The final section of the book addresses the applications to management and sustainability. By helping to understand the complexities of multispecies networks, this book provides insights into the evolution of organisms and the fate of ecosystems in a changing world.