Pollen feeding, resource allocation and the evolution of chemical defense in passion vine butterflies

Evolution of pollen feeding in Heliconius has allowed exploitation of rich amino acid sources and dramatically reorganized life history traits. In Heliconius eggs are produced mainly from adult acquired resources, leaving somatic development and maintenance to larva effort. This innovation may also have spurred evolution of chemical defense via amino acid-derived cyanogenic glycosides. By contrast, non-pollen feeding heliconiines must rely almost exclusively on larval-acquired resources for both reproduction and defense. We tested whether adult amino acid intake has an immediate influence on cyanogenesis in Heliconius. Because Heliconius are more distasteful to bird predators than close relatives that do not utilize pollen we also compared cyanogenesis due to larval input across Heliconius species and non-pollen-feeding relatives. Except for one species, we found that varying the amino acid diet of an adult Heliconius has negligible effect on its cyanide concentration. Adults denied ami...