The allometry of ornaments and weapons
Kodric-Brown, A., Sibly, R. M. and Brown, J. H. (2006) The allometry of ornaments and weapons. Proceedings of the National Academy of Sciences of the United States of America, 103 (23). pp. 8733-8738. ISSN 0027-8424
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To link to this item DOI: 10.1073/pnas.0602994103
Exaggerated male traits that have evolved under sexual selection include ornaments to attract mates and weapons to deter rivals. Data from studies of many such traits in diverse kinds of organisms show that they almost universally exhibit positive allometries. Both ornaments and weapons increase disproportionately with overall body size, resulting in scaling exponents within species that are consistently > 1.0 and usually in the range 1.5-2.5. We show how scaling exponents reflect the relative fitness advantages of ornaments vs. somatic growth by using a simple mathematical model of resource allocation during ontogeny. Because the scaling exponents are similar for the different taxonomic groups, it follows that the fitness advantages of investing in ornaments also are similar. The model also shows how selection for ornaments influences body size at first reproduction and explains why interspecific allometries have consistently lower exponents than intraspecific ones.