Geographic variation in cuticular hydrocarbon profiles in Pacific field crickets

Abstract

1. Insect cuticular hydrocarbons (CHCs) serve a role in both desiccation resistance and sexual attractiveness. These two functions are thought to be maximised by different CHC compositions, which should lead to local adaptation between populations experiencing different natural and sexual selection pressures.2. The Pacific field cricket (Teleogryllus oceanicus) is distributed throughout Oceania, including the Hawaiian and Cook Islands. In Hawaii, these crickets face strong natural selection from a parasitoid fly that has promoted the evolution of a novel male reproductive morph, dramatically altering sexual selection in the Hawaiian populations. The parasitoid and male polymorphism do not occur in the Cook Islands.3. We captured male and female T. oceanicus on two Hawaiian Islands and three Cook Islands, and quantified their CHCs. We also measured temperature and RH at our collection sites to test for associations with cricket CHC profiles.4. We discovered significant sexual dimorphism in CHC profiles, as well as differences between both island chains and particular islands. The two male reproductive morphs in Hawaii showed distinct CHC expression. There were no associations between weather variables and CHC profiles.5. Observed differences in T. oceanicus CHC profiles appear to reflect geographic isolation rather than selection in response to local and environmental and social conditions.