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Stability of genetic polymorphism in host-parasite interactions
Aurélien Tellier1, James K M Brown
1Department of Disease and Stress Biology, John Innes Centre, Colney, Norwich NR4 7UH, UK. aurelien.tellier@bbsrc.ac.uk
Proceedings. Biological Sciences
|January 26, 2007
Summary
Genetic polymorphism in host-parasite interactions is maintained by negative frequency-dependent selection (FDS). This occurs when selection strength decreases with allele frequency, common in diseases with multiple parasite generations per host.
Area of Science:
- Evolutionary biology
- Population genetics
- Immunology
Background:
- Allelic diversity is prevalent at host and parasite loci involved in recognition systems.
- Existing models propose various factors to explain genetic polymorphism in host-parasite recognition.
Purpose of the Study:
- To develop a general theory of host-parasite coevolution.
- To identify the conditions necessary for maintaining polymorphism in both host and parasite populations.
Main Methods:
- Development of a theoretical model for host-parasite coevolution.
- Analysis of frequency-dependent selection (FDS) dynamics.
Main Results:
- Coevolution inherently involves indirect frequency-dependent selection (FDS).
- Polymorphism is maintained only with negative, direct FDS, where selection strength decreases with allele frequency.
- This condition is met when parasites have multiple generations within a single host.
Conclusions:
- The developed theory provides a unifying framework for understanding polymorphism at host-parasite recognition loci.
- It encompasses previously proposed factors, including gene-for-gene interactions.
- Negative FDS, driven by multi-generational parasite life cycles, is crucial for maintaining genetic diversity in host-parasite systems.
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