Structural adaptations to diverse fighting styles in sexually selected weapons

Erin L. McCullough, Bret W. Tobalske, Douglas J. Emlen, Sean B. Carroll

Research output: Contribution to journalArticlepeer-review

70 Scopus citations


The shapes of sexually selected weapons differ widely among species, but the drivers of this diversity remain poorly understood. Existing explanations suggest weapon shapes reflect structural adaptations to different fighting styles, yet explicit tests of this hypothesis are lacking. We constructed finite element models of the horns of different rhinoceros beetle species to test whether functional specializations for increased performance under speciesspecific fighting styles could have contributed to the diversification of weapon form. We find that horns are both stronger and stiffer in response to species-typical fighting loads and that they perform more poorly under atypical fighting loads, which suggests weapons are structurally adapted to meet the functional demands of fighting. Our research establishes a critical link between weapon form and function, revealing one way male-male competition can drive the diversification of animal weapons.

Original languageEnglish
Pages (from-to)14484-14488
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number40
StatePublished - Oct 7 2014


  • Dynastinae
  • Finite element analysis
  • Functional morphology
  • Sexual selection


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