Wax, sex and the origin of species: Dual roles of insect cuticular hydrocarbons in adaptation and mating

Abstract

Evolutionary changes in traits that affect both ecological divergence and mating signals could lead to reproductive isolation and the formation of new species. Insect cuticular hydrocarbons (CHCs) are potential examples of such dual traits. They form a waxy layer on the cuticle of the insect to maintain water balance and prevent desiccation, while also acting as signaling molecules in mate recognition and chemical communication. Because the synthesis of these hydrocarbons in insect oenocytes occurs through a common biochemical pathway, natural or sexual selection on one role may affect the other. In this review, we explore how ecological divergence in insect CHCs can lead to divergence in mating signals and reproductive isolation. We suggest that the evolution of insect CHCs may be ripe models for understanding ecological speciation.

Keywords: chemical communication; cuticular hydrocarbons; desiccation; ecological adaptation; mating success; speciation.

Figure 1

Cuticular hydrocarbons (CHCs) play two critical roles in insects. They form a waxy layer on the cuticles of insects to prevent desiccation due to cuticular water loss. Some of these CHCs have roles in mating cues. (Picture of oenocytes taken from [76]).

Figure 2

Melting temperatures of CHCs are directly correlated with waterproofing properties but inversely correlated with information content.

Figure 3

Two models for how CHCs can affect both desiccation resistance and mating success. A: The direct model. Evolutionary changes in CHCs may affect both desiccation resistance and mating success when these CHCs play roles in both processes. B: The indirect model. Evolutionary changes in CHCs that affect either desiccation resistance or mating success may affect the other process by altering the production of other CHCs in the pathway.