Inducible chemical defences in animals

19 February 2014

Hettyey, Attila; Tóth, Zoltán; Van Buskirk, Josh

Phenotypic plasticity is extremely widespread in the behaviour, morphology, and life history of animals and plants. However, inducible changes in the production of defensive chemicals are described mostly in plants and surprisingly little is known about similar plasticity in chemical defences of animals. Inducible chemical defences may be common in animals because many are known to produce toxins, the synthesis of toxins is likely to be costly, and there are a few known cases of animals adjusting their toxin production to changes in environmental conditions. We outline what is known about the occurrence of inducible chemical defences in animals and argue that there is immense potential for progress in this largely neglected field. Possible directions include surveying diverse taxa to explore how general its occurrence may be and testing for selection acting on inducible chemical defences. Data on inducible chemical defences would also provide insight into life history trade-offs by enabling novel tests of how time-costs and resource-costs affect life history. If the synthesis of toxic compounds by animals proves accessible to manipulation, as it is in plants and fungi, this will open the way to refined estimates of the fitness costs of defence, ultimately providing a clearer picture of how plasticity evolves and is maintained in nature.