Data from: Arbuscular mycorrhizal fungi mediate herbivore-induction of plant defenses differently above and belowground

Plants are exposed to herbivores and symbionts above and belowground.
Herbivores aboveground alter plant defenses in both leaves and roots,
affecting plant-herbivore interactions above and belowground. Root
symbionts, such as arbuscular mycorrhizal fungi (AMF), also influence the
defenses of leaves and roots, and alter plant responses to herbivory.
However, we lack an understanding of how AMF mediate plant responses to
herbivores simultaneously in above and belowground plant tissues, despite
the ubiquity of such interactions and their consequences for ecological
communities. In a full factorial experiment, we subjected plants of four
milkweed (Asclepias) species under three levels of AMF inoculum
availability to damage by aphids (Aphis nerii), caterpillars (Danaus
plexippus), or no herbivores. We then measured foliar and root
cardenolides (chemical defenses), leaf toughness, latex exudation
(physical defenses), foliar carbon, nitrogen, and phosphorous
concentrations, plant biomass, and levels of AMF colonization of roots.
Plants inoculated with AMF generally produced tougher leaves with higher
cardenolide concentrations than did plants without AMF. In contrast, root
cardenolides were altered by AMF inoculum availability in a plant
species-specific manner. The relative induction or suppression of foliar
cardenolides and leaf toughness by herbivores was altered strongly by the
level of AMF inoculum available to plants. However, AMF did not influence
caterpillar-induction or aphid-suppression of root cardenolides. In
addition, herbivore feeding induced substantial changes in levels of AMF
colonization of roots in a plant species-specific manner. We demonstrate
that the availability of AMF in soil alters herbivore induction and
suppression of plant defenses strongly, and does so differently in above
and belowground plant tissues. Furthermore, we show that herbivore feeding
alters levels of AMF colonization substantially, completing a feedback
loop between above and belowground organisms. Our study suggests that
indirect interactions between AMF and herbivores may have community-wide
consequences by altering plant phenotype both above and belowground.