Sexual dimorphism in cuticular hydrocarbons and their potential use in mating in a bushcricket with dynamic sex roles

Abstract

Insect cuticular hydrocarbons provide desiccation resistance but may also be used in chemical signalling. Sexually dimorphic hydrocarbon blends, which may be transferred between individuals during copulation, are used especially in mate assessment. However, not all insect species produce sex-specific hydrocarbon blends, and their general utility in mate choice requires study of a broader range of species than is currently available. In the nuptial gift-giving bushcricket Kawanaphila nartee , sex roles vary depending on food availability: when food is scarce, females compete for access to males and their nuptial gifts, and when food is abundant, males compete for access to females. Given the scope for both male and female mate choice in the species, we hypothesized that their cuticular hydrocarbon profiles would differ. We characterized the cuticular hydrocarbon profiles of male and female K. nartee and found significant differences between them. Given the costly nutrient gifts provided by males at mating, we further hypothesized that males might use hydrocarbon residues left by rival males after mating to avoid investing in offspring sired by other males. Although females perfumed with male-derived hydrocarbon blends had lower mating success than control females, the difference was not statistically significant. We discuss the possible mechanisms that might favour the evolution of sexual dimorphism in cuticular hydrocarbon blends in this species. • Sexual dimorphism in cuticular hydrocarbons occurs in a sex role reversing insect. • Sexual dimorphism in hydrocarbons is not used by males in mate discrimination. • The dimorphism nevertheless provides a mechanism for sex discrimination. • The dimorphism may be used in mate choice by one or both sexes.