Anticipating critical transitions in complex, multi-species ecosystems remains a key challenge because early warning signals (EWS) are not uniformly expressed across species. Using Ecopath with Ecosim models, we analyzed 127 natural marine ecosystems to identify reliable “early warning species” for critical transitions. By reconstructing species biomass dynamics and applying segmented regression to detect broken points, we quantified the early warning capacity of each species by the slope of the first segmented regression line. We found that species at the extremes of the trophic spectrum—top predators—consistently provide the strongest and earliest warning signals. These early warning species are typically central to food web structure, making them ecologically informative sentinels of system-wide instability. Our results clarify species-level responses to critical transitions and offer a practical framework for monitoring and managing marine ecosystems under accelerating environmental change.
Predation risk is an important mediator of trophic interactions. Predation risk can induce behavioral responses in prey, such as reduced feeding and reproductive capacity, that can scale up to affect prey population size, known as non-consumptive effects. Understanding the impact of non-consumptive effects on insect systems is of increasing interest in part due to the economic importance of many insect herbivores. Stylet-feeding insects are a critical herbivore feeding guild containing many notable pest species and vectors of plant viruses. However, stylet feeding is unable to be measured without the use of the electrical penetration graph technique and has only recently been explored in the context of predation risk research. By using the electrical penetration graph in combination with a novel enclosure technique, we aimed to quantify aphid stylet-feeding behavior in the presence of a parasitic wasp. Interpretation of the electrical penetration graph outputs were further informed by paired behavioral observation assays to determine whether aphid physical movements could explain the differences observed in feeding behaviors. Wasp presence increased the time it took aphids to reach the phloem and establish long-term feeding. In the behavioral observations, aphids remained motionless for longer in the presence of parasitic wasps. This suggests that reduced feeding activity could be a key driver of the non-consumptive effects of parasitic wasps on aphids. Identifying novel ways to integrate EPG recordings in predation risk research greatly expands our capacity to understand mechanisms mediating predator-prey interactions with stylet-feeding herbivores.
Understanding how abiotic drivers and biotic interactions jointly regulate food-web structure is central to wetland ecology, yet mechanistic, hypothesis-driven studies remain limited for tropical floodplain systems. This study examined the food-web dynamics of Bhaluka Beel, a tropical freshwater wetland in eastern India, by explicitly testing predictions derived from bottom-up, top-down, habitat-mediated, and stress-response hypotheses. Seasonal variation in physicochemical parameters, primary productivity, and multiple biotic compartments—phytoplankton, zooplankton, macrophytes, benthos, aquatic insects, fishes, amphibians, reptiles, birds, and aquatic mammals—was quantified. Structural equation modeling (SEM) was used to evaluate hypothesized trophic relationships within a conceptual food-web framework and adjacency matrix representation was applied to assess interaction strength and network topology. Results revealed strong bottom-up coupling between nutrient availability, primary productivity, and planktonic biomass, together with evidence consistent with top-down regulation through strong fish–zooplankton predator–prey interactions. Macrophytes also appeared to contribute to food-web stability by increasing habitat complexity and providing alternative energy pathways. Abiotic stress associated with organic enrichment and lower dissolved oxygen was linked to weaker higher-trophic interactions, leading to partial simplification of the food web. These findings provide mechanistic insights into trophic regulation in floodplain wetlands and offer a methodological framework for assessing ecosystem responses to environmental change.
