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Compensatory traits can explain the concave cost function of purely sexual traits
1Department of Environmental Science Ishikawa Prefectural University Nonoichi Ishikawa Japan.
Ecology and Evolution
|January 16, 2024
Summary
Ornamentation experiments may mislead by ignoring compensatory traits. Overcompensation can worsen performance, meaning concave cost functions don't solely indicate viability selection for ornamentation.
Area of Science:
- Evolutionary biology
- Animal behavior
- Biomechanics
Background:
- Experimental studies on the cost of ornamentation often measure performance to infer evolutionary pressures (sexual vs. viability selection).
- A classic study on barn swallow tail feathers suggested viability selection shapes ornamentation based on a concave cost function.
- This interpretation relies on the assumption that compensatory traits do not negatively impact performance.
Purpose of the Study:
- To investigate whether sexual selection alone can produce a concave cost function for ornamentation.
- To determine if compensatory traits, previously overlooked, can influence the interpretation of experimental results on ornamentation costs.
- To re-evaluate the inference of evolutionary forces from concave cost functions in the context of ornamentation.
Main Methods:
- A simple "toy model" experiment was designed to simulate the evolution of ornamentation under sexual selection.
- A mathematical model was employed to reinforce the findings from the toy model experiment.
- The study specifically considered the impact of compensatory traits and the phenomenon of 'overcompensation'.
Main Results:
- Ornamentation evolved purely through sexual selection can generate a concave cost function when compensatory traits are present.
- The presence of compensatory traits, particularly 'overcompensation,' can lead to reduced overall body performance in individuals with reduced ornaments.
- This overcompensation effect challenges the direct link between concave cost functions and viability selection.
Conclusions:
- Concave cost functions observed in ornamentation studies cannot be solely attributed to viability selection.
- The overlooked concept of 'overcompensation' in compensatory traits can confound experimental interpretations.
- Future research on ornamentation evolution must account for the complex interplay of sexual selection, viability selection, and compensatory mechanisms.
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