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Social life-history response to individual immune challenge of workers of Bombus terrestris L.: a possible new cooperative phenomenon

Authors

  • Yannick Moret,

    Corresponding author
      Correspondence and present address: Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK. E-mail: y.moret@sheffield.ac.uk
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  • Paul Schmid-Hempel

    1. Eidgenössische Technische Hochschule (ETH) Zürich, Ecology and Evolution, ETH-Zentrum, NW, CH-8092 Zürich, Switzerland
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Correspondence and present address: Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK. E-mail: y.moret@sheffield.ac.uk

Abstract

Parasites typically reduce host survival or fecundity. To minimize fitness loss, hosts can make temporal adjustments of their reproductive effort. To date such plastic shifts of life-history traits in response to parasitism are only known from solitary organisms where infected individuals can react by themselves. In the case of social insects, where brood care and reproductive effort is shared between reproductive individuals (typically the queen) and workers, adjustments of the reproductive effort would depend on collective decision-making. We tested for this possibility by experimentally activating the immune response of individual workers in colonies of the bumblebee, Bombus terrestris L. This induction resulted, in combination with environmental conditions, in a reduction of fitness of the social unity (i.e. colony success, measured by number and biomass of offspring) and a collective response towards earlier reproduction. As both phenomena are expressed at the level of the colony, the result suggests that key elements of the use of immune defence have been maintained through the evolutionary transition to sociality.

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