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36849 results in Cambridge Textbooks

Page 1503 of 1843

  • 12 - Parasite population ecology

  • Timothy M. Goater, Cameron P. Goater, University of Lethbridge, Alberta, Gerald W. Esch, Wake Forest University, North Carolina
  • Book:
    Parasitism
    Published online:
    28 May 2018
    Print publication:
    16 December 2013, pp 335-355

  • Summary

    General considerations

    Our previous chapters focused on the functional morphology, life cycles and ecology of a wide range of animal parasites. One of our aims in these chapters was to highlight the complexity and fascination of the parasitic life style. Another was to introduce the idea that the seemingly infinite diversity of parasite life cycles and adaptations could be interpreted under an ecological umbrella. Armed with this background knowledge, we now consider unifying principles of ecology and evolution that can be applied to the phenomenon of parasitism.

    We begin our transition with a consideration of the complex nature of parasite populations and the general ecological characteristics of the individuals that comprise them. We highlight the nature of enquiry at this level by first considering two examples. In a field survey, Cornwell & Cowan (1963) monitored the transmission of gut helminths into 180 canvasback ducks, Aythya valisineria, sampled from a small wetland in western Canada. The authors controlled for sampling heterogeneity by restricting their collections to ducklings within individual clutches. Their results showed that even within a single clutch, individual siblings harbored between 90 and 6000 worms! In another field survey, Valtonen et al. (2004) censused adult acanthocephalan populations in individual ringed seals, Phoca hispida, collected from the Baltic Sea. Although the collections spanned a 22-year period when the seal and intermediate host populations varied extensively, the prevalence of acanthocephalans was always 100% and the mean number of worms fluctuated within a single order of magnitude. Thus, on the one hand, mean parasite infrapopulation sizes can vary tremendously, even within very narrow spatial and temporal scales. On the other hand, population sizes can be remarkably stable, barely fluctuating around an equilibrium value. Characterizing this extreme variation at both narrow and broad temporal and spatial scales and understanding the underlying mechanisms that determine it are the central objectives of parasite population ecologists and ecological epidemiologists.

Page 1503 of 1843