Data from: Aboveground herbivory by red milkweed beetles facilitates above- and below-ground conspecific insects and reduces fruit production in common milkweed
Erwin, Alexis C.; Züst, Tobias; Ali, Jared G.; Agrawal, Anurag A. (2015), Data from: Aboveground herbivory by red milkweed beetles facilitates above- and below-ground conspecific insects and reduces fruit production in common milkweed, Dryad, Dataset, https://doi.org/10.5061/dryad.pg4k8
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 above- and belowground. Initial aboveground herbivory increased root damage and larval survival, suggesting an increase in root quality following leaf herbivory. Initial belowground herbivory did not affect the performance of later-feeding larvae, indicating limited importance of induced root cardenolides and competition between clutches of T. tetraophthalmus. 4. In a natural milkweed population, initial aboveground herbivory attracted conspecific adults and milkweed leaf beetles (Labidomera clivicollis), and ultimately reduced fruit production by 33%. Nonetheless, the probability of damage by monarch caterpillars (Danaus plexippus) was reduced on plants initially damaged by T. tetraophthalmus aboveground, perhaps due to reduced oviposition following induced plant responses. 5. Synthesis: Induced plant responses of common milkweed to aboveground damage by adult T. tetraophthalmus both facilitate further damage by adults, and enhance the performance of their root-feeding larvae, most likely as a result of host plant manipulation. Although the same induction reduced monarch herbivory, the net effect of these interactions was reduced fruit production. Host plant manipulation may be especially common by specialist herbivores that have sequential above- and belowground life stages.