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3 results

  • Chapter Ten - Parasite-mediated selection in red grouse – consequences for population dynamics and mate choice

  • from Part II - Understanding between-host processes
  • Edited by Kenneth Wilson, Lancaster University, Andy Fenton, University of Liverpool, Dan Tompkins
  • Book:
    Wildlife Disease Ecology
    Published online:
    28 October 2019
    Print publication:
    14 November 2019, pp 296-320

  • Summary

    Parasites inflict many costs on their hosts. Understanding host–parasite relationship eco-evolutionary dynamics needs appreciation of how parasites affect individual fitness, survival and reproductive potential, and how they combine to influence population demography, dynamics and viability; also, how these processes drive microevolutionary processes that define natural and sexual selection. We synthesise work on the relationship between the red grouse and its main parasite, a gastrointestinal nematode. At individual level, we show how parasites impose a physiological cost, measured by immunosuppression and increased oxidative stress, and how their impact varies depending on contexts. We describe how parasite infection constrains expression of sexually selected traits and summarise how relationships between parasite, host and environment shape host population demography and dynamics. Genetic analyses in red grouse suggest nematode burden is moderately heritable, underpinned by a potentially large array of genes involved in the immune system, energy balance and broader homeostatic processes. There is no clear association between allele frequencies among populations and differences in nematode burdens. Possibly, beneficial alleles for parasite resistance cannot spread through the population due to the strong diversifying e?ects of gene ?ow and genetic drift.

  • Resistance rather than tolerance explains survival of savannah honeybees (Apis mellifera scutellata) to infestation by the parasitic mite Varroa destructor

  • URSULA STRAUSS, VINCENT DIETEMANN, HANNELIE HUMAN, ROBIN M. CREWE, CHRISTIAN W. W. PIRK
  • Journal:
    Parasitology / Volume 143 / Issue 3 / March 2016
    Published online by Cambridge University Press:
    22 December 2015, pp. 374-387

  • Varroa destructor is considered the most damaging parasite affecting honeybees (Apis mellifera L.). However, some honeybee populations such as the savannah honeybee (Apis mellifera scutellata) can survive mite infestation without treatment. It is unclear if survival is due to resistance mechanisms decreasing parasite reproduction or to tolerance mechanisms decreasing the detrimental effects of mites on the host. This study investigates both aspects by quantifying the reproductive output of V. destructor and its physiological costs at the individual host level. Costs measured were not consistently lower when compared with susceptible honeybee populations, indicating a lack of tolerance. In contrast, reproduction of V. destructor mites was distinctly lower than in susceptible populations. There was higher proportion of infertile individuals and the reproductive success of fertile mites was lower than measured to date, even in surviving populations. Our results suggest that survival of savannah honeybees is based on resistance rather than tolerance to this parasite. We identified traits that may be useful for breeding programmes aimed at increasing the survival of susceptible populations. African honeybees may have benefited from a lack of human interference, allowing natural selection to shape a population of honeybees that is more resistant to Varroa mite infestation.