Phytochemical diversity and seasonality are associated with a critical transition in plant–herbivore network structure

Understanding critical transitions in ecological systems is fundamental for addressing various natural phenomena, from population outbreaks to sudden ecosystem collapses. Ecological interactions are key drivers of these transitions, and theory suggests that the networks formed by these interactions can undergo their own critical transition. By examining interactions between plant individuals and insect species in a tropical forest, we first identified a critical network structural transition between the rainy and dry seasons. Next, we showed that seasonal changes and the phytochemical diversity of plants are associated with this transition. Finally, we quantified the consequences of the critical transition, which significantly increases the number of pathways and the potential for cascading effects among plants and herbivores in the network. Our findings reveal that ecological networks can experience abrupt changes on shorter timescales than previously recognized, with profound implications for cascading effects and the impacts of human-induced perturbations on the stability of ecological assemblages.