The Effect of Dietary Fatty Acids on the Cuticular Hydrocarbon Phenotype of an Herbivorous Insect and Consequences for Mate Recognition

The cuticular hydrocarbon (CHC) profile of the mustard leaf beetle Phaedon cochleariae is known to mediate mate recognition and is dependent on food plant species; beetles previously were shown to prefer mates that fed on the same plant species and which have a similar CHC pattern. In order to elucidate whether the pattern of ingested fatty acids affects the CHC pattern of P. cochleariae adults, we fed beetles: (a) with two different host plant species differing in fatty acid profile; and (b) artificial diets differing mainly in their composition of mono-, di-, and triunsaturated fatty acids. Analyses of the beetles' CHCs revealed that ingestion of different fatty acid blends results in quantitative effects on the beetle's straight-chain and methyl-branched CHCs. Interestingly, CHC patterns of males and females were affected differently by ingestion of fatty acids. In contrast to the effect on mating caused by feeding on different host plant species, beetles that were fed with different artificial diets, leading to different beetle CHC profiles, did not exhibit mating preference. We suggest that the occurrence of CHC-dependent assortative mating in P. cochleariae does not depend on the dietary fatty acids offered to the beetles in this study, but on other food constituents that affect CHC biosynthesis.