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Updated: Aug 8, 2026
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Dissection, MicroCT Scanning and Morphometric Analyses of the Baculum
Published on: March 19, 2017
The allometry of ornaments and weapons
Astrid Kodric-Brown1, Richard M Sibly, James H Brown
1Department of Biology, University of New Mexico, Albuquerque, NM 87131, USA. kodric@unm.edu
Summary
Sexual selection drives exaggerated male traits like ornaments and weapons, which grow disproportionately with body size. This consistent scaling across species suggests similar fitness benefits for ornamentation versus growth.
Area of Science:
- Evolutionary biology
- Zoology
- Ecology
Background:
- Sexual selection favors exaggerated male traits (ornaments, weapons) for mate attraction and rival deterrence.
- These traits often exhibit positive allometry, increasing disproportionately with body size across diverse species.
Purpose of the Study:
- To investigate the relationship between scaling exponents of male ornaments/weapons and fitness advantages.
- To model resource allocation between ornamentation and somatic growth during ontogeny.
- To explain patterns of allometry within and between species.
Main Methods:
- Analysis of existing data on trait scaling exponents from various organisms.
- Development of a mathematical model for resource allocation and ontogenetic growth.
- Comparison of intraspecific and interspecific allometric scaling.
Main Results:
- Scaling exponents for ornaments and weapons consistently exceed 1.0 (typically 1.5-2.5) within species.
- Model demonstrates that similar scaling exponents imply similar fitness advantages for ornamentation across taxa.
- Selection for ornaments influences body size at first reproduction.
- Interspecific allometries show consistently lower exponents than intraspecific ones.
Conclusions:
- Positive allometry of exaggerated male traits reflects a balance between sexual selection and somatic growth.
- The universality of scaling exponents suggests conserved fitness benefits of ornamentation.
- Allometric patterns provide insights into the evolution of body size and reproductive strategies.
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