Meeting Abstract

S2.2-3  Saturday, Jan. 4 11:30  Mechanisms of Honest Signaling in Condition Dependent Growth in Exaggerated Traits LAVINE, L.C.*; EMLEN, D. J.; DUKE, A.; WARREN, I.A.; GOTOH, H.; Washington State University; University of Montana; University of Montana; University of Bristol; Washington State University lavine@wsu.edu

Many male animals wield ornaments or weapons of exaggerated proportions. These traits are often used for mate choice, or to deter rival males, because they act as reliable signals of the condition of individual males. Only the best-quality animals produce full-sized ornaments or weapons. But why don’t males cheat? How can signal traits evolve that are resistant to invasion by cheaters who fake attractive signals? We expect the answer to be found in the intricate and dynamic mechanistic systems that link growth with condition. Using the sexually dimorphic rhinoceros beetle as our model, we present evidence suggesting that exaggerated sexually-selected signal traits arise when specific structures become extra-sensitive to physiological signals like insulin or insulin-like growth factors. 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 byproduct of the growth mechanism may explain why trait exaggeration has evolved so many different times in the context of sexual selection.