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Published on: August 29, 2013
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Population age structure shapes selection on social behaviour in a long-lived insect
Phoebe A Cook1,2,3, Robin A Costello1,2,4, Edmund D Brodie Iii1,2
1Department of Biology, University of Virginia, Charlottesville, VA, USA.
Summary
Population age structure significantly impacts social behaviors and fitness in beetles. Older individuals generally have higher reproductive success, but social interactions with older partners can incur fitness costs, especially for males.
Area of Science:
- Evolutionary Biology
- Behavioral Ecology
- Demography
Background:
- Social traits are subject to context-dependent selection, yet the specific factors shaping this selection remain largely unknown.
- The age of social partners is a potential, understudied factor influencing the fitness consequences of social interactions and sociality.
Purpose of the Study:
- To investigate how population age structure influences individual fitness and sexual selection on social network traits.
- To test the hypothesis that the fitness consequences of social interactions depend on the age of social partners.
Main Methods:
- Experimental manipulation of age composition in populations of the forked fungus beetle (Bolitotherus cornutus).
- Creation of 12 replicate populations with either young or old age structures.
- Assessment of fitness and social network traits across different age structures.
Main Results:
- Fitness is linked to age variance at individual, social partner, and population levels.
- Older individuals exhibit higher reproductive success; males incur fitness costs with older males; females have lower fitness in older populations.
- Population age structure alters selection on female social network position, with positive selection for female sociality occurring only in older populations.
Conclusions:
- Population age structure is a critical, understudied demographic variable shaping evolutionary pressures on social behavior.
- Age-related interactions significantly influence fitness and sexual selection, highlighting the importance of age structure in social evolution.
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