The growth on different stored legume species affects the profiles of cuticular hydrocarbon (CHC) in Acanthoscelides obtectus (Say)

Acanthoscelides obtectus (Say) (Coleoptera: Chrysomelidae: Bruchinae) is a widespread pest of stored products from Fabaceae family. The evolution of this species is associated with common bean domestication and the ability to invade other hosts in storages. To analyze the role of diverse nutrition in the ability of insects to shift to another host species we tested the effects of nutrition history on composition of cuticular hydrocarbons (CHCs), the compounds that have various ecological and reproductive functions in insects. The study was performed on A. obtectus laboratory populations which were bred for 51 generations either on common bean, Phaseolus vulgaris (L.), or on chickpea, Cicer arietinum (L.), a novel and less suitable species for larval development. To obtain conclusions about short-term nutritional effects, we tested whether exposure of seed weevils to alternative hosts for just one generation might influence CHC composition. Gas chromatography and gas chromatography–mass spectrometry analyses were performed and compounds' relative abundances were computed from the corresponding GC-FID peak areas. A total of 21 compounds were identified, among which 38% showed significant abundance differences between selection regimes and for 33% of compounds short-term developmental effects were revealed. All except three compounds showed significant differences between genders. We hypothesized that long-term changes in quantitative levels of specific CHC compounds were the results of diverse selection pressures on weevils' metabolic pathways induced by chemically divergent hosts. However, long-term adaptations to host species did not influence the ability of A. obtectus to quickly respond to chemical specificities of novel hosts (i.e., short-term effects were significant) which could be one of the major reasons for the great expansiveness of this species. Differences in relative CHCs abundances between sexes implied their roles in chemical communication and mate recognition systems.

► Acanthoscelides obtectus (Say) is a widespread pest of stored legume products. ► Selection on diverse legume species change quantitative levels of compounds in CHC profiles. ► CHC levels revealed the ability of bean weevil to respond to chemical specificities of novel hosts. ► Differences between sexes indicate that CHCs have roles in chemical communication.