Host plant chemistry enhances herbivore cellular immunity with
differential effectiveness against two parasitoid species
- Enakshi Ghosh,
- Paul Ode,
- Ryan Paul
Abstract
Insect herbivores must simultaneously balance bottom-up effects of plant
defensive chemistry and the top-down effects of natural enemies. At the
intersection of these effects are herbivore immune systems, an herbivore
trait that has largely been overlooked in studies of plant-insect
interactions. Counter to the majority of studies showing that herbivores
feeding on plants containing higher levels of toxins are
immunocompromised, we demonstrate that Pieris rapae caterpillars feeding
on more toxic host plants have enhanced cellular immunity at the cost of
reduced growth rates and body size. However, whether enhanced immune
systems are effective defense against parasitoids depends on parasitoid
identity. Whereas enhanced immunity provided increased protection
against the parasitoid Cotesia glomerata, it did not provide protection
against C. rubecula that suppressed and evaded the host's immune system.
Our study demonstrates that both herbivore immunity and species identity
of trophic participants are crucial in determining the structure of
multitrophic interactions.