Eco-immunology of trophic interactions

Whether herbivore traits are primarily shaped by resource limitation (including plant traits that reduce palatability) or the activities of consumers (e.g., predators, parasites, pathogens) is a long-standing debate in ecology. Historically, plant traits such as anti-herbivore chemistry have been of primary importance in determining whether herbivores feed on a given plant. Yet, natural enemies have long been appreciated to exert significant top-down effects on herbivore populations. While plant-herbivore and herbivore-natural enemy interactions have been the subject of countless studies over the past decades, we still know surprisingly little about how insect herbivores simultaneously contend with them. At the intersection of these interactions are herbivore immune systems, traits that have been largely overlooked in studies of plant-insect interactions. In my talk, I will discuss how plant defense chemistry modulates herbivore immunity along with other life-history traits, thus influencing interactions with higher trophic levels. Further, I will provide empirical proof of how concentrations of plant defense toxins in caterpillar diets are correlated with levels of immunocompetence in caterpillars. I will discuss why it is essential to study caterpillar immune responses while studying trophic interactions. Finally, I aim to emphasize that eco-immunological studies of herbivore immune systems offer compelling opportunities to examine the mechanisms of how herbivores simultaneously defend against their own natural enemies while coping with plant defense chemicals. Such studies have important implications for pest management and conservation efforts, as they can inform strategies for reducing the impact of herbivores on crops and for protecting vulnerable species from predators and parasites.