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Systemic Bacterial Infection and Immune Defense Phenotypes in Drosophila Melanogaster
Published on: May 13, 2015
Sexual selection and immune function in Drosophila melanogaster.
Kurt A McKean1, Leonard Nunney
1Department of Biological Sciences, State University of New York at Albany, Albany, New York 12222, USA. kmckean@albany.edu
Evolution; International Journal of Organic Evolution
|December 12, 2007
Summary
Intense sexual selection reduces immune function in fruit flies, suggesting disease susceptibility limits sexual competitiveness. This trade-off impacts both sexes, highlighting a genetic conflict in evolutionary adaptation.
Area of Science:
- Evolutionary biology
- Immunology
- Genetics
Background:
- Immune function evolves influenced by genes directly impacting immunity and indirectly affecting immunocompetence.
- Sexual selection may trade-off with immunocompetence due to resource allocation conflicts.
- The immunocompetence handicap hypothesis (ICHH) predicts exaggerated sexual dimorphism and reduced condition-dependent immunity under sexual selection.
Purpose of the Study:
- To test the evolutionary trade-off between sexual selection and immunocompetence in Drosophila melanogaster.
- To investigate if intensified sexual selection leads to immunological sexual dimorphism.
- To examine evolutionary changes in condition-dependent immunocompetence.
Main Methods:
- Intensified sexual selection applied to laboratory populations of Drosophila melanogaster for 58 generations via male-biased sex ratios.
- Comparison of immune function between sexually selected and control (equal sex ratio) lines.
- Analysis of sexual dimorphism in immune function and condition-dependent immunocompetence.
Main Results:
- Sexually selected males exhibited reduced immune function compared to control males, supporting the trade-off hypothesis.
- No evidence of increased immunological sexual dimorphism was found; females showed similar immune reductions.
- No evolutionary changes in condition-dependent immunocompetence were observed, contrary to ICHH predictions.
- Males successful in mating (IS) showed reduced immune function relative to unsuccessful males (IU).
Conclusions:
- Increased disease susceptibility is a significant cost limiting sexual competitiveness under intense sexual selection.
- The high intersex genetic correlation suggests a conflict, preventing males from reaching their optimal sexual selection levels.
- Phenotypic correlations largely reflect the genetic correlations observed in the selection experiment.
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