Drought restructures multitrophic food webs through cascading eco-physiological constraints

Abstract

Ecological communities are linked not only by energy flows, but also by sensory and behavioral pathways that allow organisms to locate, recognize, and interact with one another. Environmental stressors such as drought may disrupt these pathways by altering both resource availability and interactions that regulate both population and community dynamics. While species-level responses to drought are well documented, far less is understood about how drought-driven changes in plant resources initiate bottom-up effects that cascade through multiple trophic levels. Here, we tested how drought affects a plant-herbivore-carnivore system by quantifying plant physiological changes and their cascading effects on herbivore performance, nutritional quality, and carnivore behavior. Drought reduced plant growth and stomatal conductance, which lowered herbivore feeding efficiency, survival, and reproduction. Herbivores feeding on drought-stressed plants also displayed lower protein content and biomass. Drought also suppressed the emission of herbivore-induced plant volatiles (HIPVs), limiting the chemical cues carnivores use to locate prey. Despite higher prey consumption rates in no-choice assays, carnivores suppressed herbivore populations less effectively under drought. At the community level, these disruptions caused disproportionate declines in arthropod abundance and diversity, particularly among carnivores, leading to trophic simplification. These findings show that drought not just reduce resource availability, it disrupts chemical cues and trophic feedbacks that maintain food web structure. By linking changes in resource limitations to community-level responses, this study demonstrates how environmental stressors can weaken top-down control and destabilize multitrophic dynamics. Predicting ecological resilience depends not only on responses but on how stress disrupts the information signals that maintain ecosystem services and function.