Leaf beetle larvae: Host Change Alters Toxic Cocktail

Larvae of the leaf beetle Chrysomela lapponica feed on birches or willows. Both beetle populations utilize precursor molecules of the plants to produce chemical defenses. As a toxin, the willow population produces salicylaldehyde. The birch population does not produce salicylaldehyde, since birches do not contain the precursor salicin. During evolution this resulted in a defect aldehyde producing enzyme, a salicylalcohol oxidase. The strong association of the leaf beetles with their host plants can be considered as the beginning of a newly emerging species.