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Allometry of Ornaments and Weapons

  Kodric-Brown, A., R. M. Sibly, and J. H. Brown. 2006. The allometry of
    ornaments and weapons. _Proceedings of the National Academy of Sciences,
    Philadelphia_ 103(23):8733-8738. [Published online before print May 26,
    2006, 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
   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
   allocation during ontogeny. Because the scaling exponents are similar for
   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."

  One must consider whether this study may actually apply to animals most of us
are all more familiar with on this list, and whether dinosaurs actually show a
male-scaling upwards of "equippage."


Jaime A. Headden

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)

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