A Mechanism of Extreme Growth and Reliable Signaling in Sexually Selected Ornaments and Weapons

Journal club: Evolutionary ecology forum

Topic: Emlen et al. 2012 Science 337 860-864


Many male animals wield ornaments or weapons of exaggerated proportions. We propose that increased cellular sensitivity to signaling through the insulin/insulin-like growth factor (IGF) pathway may be responsible for the extreme growth of these structures. We document how rhinoceros beetle horns, a sexually selected weapon, are more sensitive to nutrition and more responsive to perturbation of the insulin/IGF pathway than other body structures. We then illustrate how enhanced sensitivity to insulin/IGF signaling in a growing ornament or weapon would cause heightened condition sensitivity and increased variability in expression among individuals—critical properties of reliable signals of male quality. The possibility that reliable signaling arises as a by-product of the growth mechanism may explain why trait exaggeration has evolved so many different times in the context of sexual selection.

Published Aug. 21, 2012 10:54 AM - Last modified Aug. 24, 2012 8:53 AM