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Parasites shape the optimal investment in immunity
Barbara Tschirren1, Heinz Richner
1Evolutionary Ecology Group, Zoological Institute, University of Bern, Switzerland. barbara.tschirren@unsw.edu.au
Proceedings. Biological Sciences
|June 23, 2006
Summary
Investing in immune function comes at a cost to growth, especially in young animals. However, enhanced immunity can improve growth rates when parasite pressure is high, demonstrating a crucial trade-off.
Area of Science:
- Ecology
- Evolutionary Biology
- Animal Physiology
Background:
- Optimal immune system function involves resource allocation trade-offs between immunity, growth, and reproduction.
- Young animals prioritize growth and competitiveness, suggesting a predicted trade-off between growth and immune function due to parasite pressure.
Purpose of the Study:
- To experimentally assess the costs and benefits of investing in immune defense in a wild bird population.
- To investigate the parasite-mediated allocation trade-off between growth and immune function.
Main Methods:
- Field study on nestling great tits (Parus major).
- Dietary supplementation with methionine to boost immune defense.
- Manipulation of ectoparasite (Ceratophyllus gallinae) abundance in nests.
Main Results:
- Methionine supplementation led to slower growth initially, indicating an immediate cost of immune boosting.
- Nestlings with boosted immunity exhibited faster growth rates under parasite pressure compared to controls.
- This demonstrates both the costs and benefits of immune investment.
Conclusions:
- Host defense evolution is governed by a parasite-mediated allocation trade-off between growth and immune function.
- Resource allocation to immunity impacts growth, with benefits realized under specific environmental pressures like parasitism.
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