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Experimentally activated immune defence in female pied flycatchers results in reduced breeding success

  • P Ilmonen
  • T Taarna
  • Dennis Hasselquist
Publishing year: 2000
Language: English
Pages: 665-670
Publication/Series: Royal Society of London. Proceedings B. Biological Sciences
Volume: 267
Issue: 1444
Document type: Journal article
Publisher: Royal Society

Abstract english

Traditional explanations for the negative fitness consequences of parasitism have focused on the direct pathogenic effects of infectious agents. However, because of the high selection pressure by the parasites, immune defences are likely to be costly and trade off with other fitness-related traits, such as reproductive effort. In a field experiment, we immunized breeding female flycatchers with non-pathogenic antigens (diphtheria-tetanus vaccine), which excluded the direct negative effects of parasites, in order to test the consequences of activated immune defence on hosts' investment in reproduction and self-maintenance. Immunized females decreased their feeding effort and investment in self-maintenance (rectrix regrowth) and had lower reproductive output (fledgling quality and number) than control females injected with saline. Our results reveal the phenotypic cost of immune defence by showing that an activated immune system per se can lower the host's breeding success. This may be caused by an energetic or nutritional trade-off between immune function and physical workload when feeding young or be an adaptive response to 'infection' to avoid physiological disorders such as oxidative stress and immunopathology.


  • Biological Sciences


  • Immunoecology
  • Molecular Ecology and Evolution Lab
  • ISSN: 1471-2954
Dennis Hasselquist
E-mail: dennis [dot] hasselquist [at] biol [dot] lu [dot] se



+46 46 222 37 08



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