Aboveground herbivory by red milkweed beetles facilitates above- and below-ground conspecific insects and reduces fruit production in common milkweed

1. Initial herbivory and induced plant responses can influence subsequent above- and belowground herbivore attack. When two life stages of the same herbivore damage different plant parts sequentially, there is strong potential for plants to respond with induced plant defense against the later attacker. Alternatively, the earlier attacker could manipulate the host plant to facilitate the later-feeding life stage. 2. We studied herbivory by foliage-feeding adults and root-feeding larvae of the red milkweed beetle (Tetraopes tetraophthalmus) on common milkweed (Asclepias syriaca) in laboratory and field experiments. We applied factorial above- and belowground herbivory treatments to test for induced responses, effects on later-feeding conspecific larvae, and damage by naturally colonizing herbivores, including adult T. tetraophthalmus. 3. We found that the inducibility of toxic cardenolides was systemic across the root-shoot barrier, with the highest concentrations in plants damaged both a...