title: A mechanism of extreme growth and reliable signaling in sexually selected ornaments and weapons.
abstract: 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.
authors: Division of Biological Sciences, The University of Montana, 104 Health Science Building, Missoula, MT 59812, USA. doug.emlen@mso.umt.edu
authors: Douglas J
authors: DJ
authors: Emlen
authors: Ian A
authors: IA
authors: Warren
authors: Annika
authors: A
authors: Johns
authors: Ian
authors: I
authors: Dworkin
authors: Laura Corley
authors: LC
authors: Lavine
mesh_terms: D000818:Animals; D001517:Coleoptera / Q000033:anatomy & histology* / Q000235:genetics / Q000254:growth & development*; D055785:Gene Knockdown Techniques; D006733:Horns / Q000033:anatomy & histology* / Q000254:growth & development*; D007328:Insulin / Q000502:physiology; D008297:Male; D052586:Mating Preference, Animal; D008969:Molecular Sequence Data; D011972:Receptor, Insulin / Q000235:genetics / Q000502:physiology*; D015398:Signal Transduction; D013002:Somatomedins / Q000502:physiology
chemical_list: D007328:Insulin; D013002:Somatomedins; D011972:Receptor, Insulin