Costs and the Diversification of Exaggerated Animal Structures
Douglas J. Emlen
Sexual selection can favor production of extravagant ornaments and
weapons in the contest for access to the opposite sex. Existing
explanations for the diversity of sexually selected structures focus on
reproductive benefits conferred by particular ornament or weapon
morphologies. Here, I show that costs of weapon production also may
drive patterns of weapon evolution. In beetles, production of horns
reduces the size of neighboring morphological structures (antennae,
eyes, or wings, depending on the location of the horns), and these
tradeoffs reveal unexpected functional associations between ecology and
horn morphology. This study illustrates a critical but overlooked role
of costs in sexual selection and has implications for understanding the
evolution of animal morphology.
Division of Biological Sciences, University of Montana, Missoula,
MT 59812-1002, USA. E-mail: demlen{at}selway.umt.edu