Standard metabolic rate (SMR) and maximum metabolic rate (MMR) define the energetic limits of aerobic metabolism in fishes and are increasingly recognized as flexible traits linked to life history variation. Yet the factors driving intraspecific variation in how SMR and MMR scale with body mass and temperature remain unresolved. We assessed mass- and temperature-scaling relationships in SMR, MMR and aerobic scope of walleye (Sander vitreus) using data from multiple intermittent-flow respirometry experiments conducted from 2020 to 2025. The dataset included wild fish from Lake Erie, Lake Ontario, and Rice Lake, and hatchery-reared individuals of Lake Ontario origin (n = 207). Additional MMRSwim estimates from swim tunnel respirometry (n = 33) were compared with MMRRecovery estimates obtained from a chase and air exposure protocol. Together, body mass and temperature explained 94.7
Understanding how niche-based and neutral processes shape biological communities is a central objective in ecology, particularly in extreme and poorly explored environments such as large subterranean systems. Here, we investigated the mechanisms structuring terrestrial invertebrate communities in the one of the most extensive and voluminous cave systems in South America. Sampling across 56 sectors (30 m²) and 168 quadrats (1 m²) revealed 123 terrestrial invertebrate species. Complementary intuitive searches conducted throughout the cave, combined with standardized sampling, indicated that the system harbors at least 23 obligate cave species, supporting its recognition as a new hotspot of subterranean biodiversity. Total species richness, as well as the richness of non-troglobitic species, increased with resource availability and shelter availability, indicating a strong influence of niche partitioning. In contrast, troglobitic species richness declined markedly with increasing distance from aquatic environments, highlighting microclimatic stability as a key environmental filter. Beta diversity was primarily structured by microclimatic stability and resource availability, whereas geographic distance and cave identity had comparatively minor effects, suggesting that dispersal does not represent a major constraint on species distribution within this highly connected system. Resource gradients promoted species turnover in troglobitic assemblages, while richness differences predominated in non-troglobitic assemblages. Overall, our findings indicate that community assembly in large cave systems emerges from the joint action of environmental filtering and niche partitioning, with responses varying across spatial scales and degrees of ecological specialization. These results reinforce the conservation importance of high-volumnous cave systems as unique environments that harbor highly diverse and specialized biotas.
Eastern Boundary Upwelling Systems (EBUS) are among the most productive marine ecosystems, largely because of the upwelling of cold, nutrient-rich seawater into coastal areas. However, the influence of upwelling on biomolecule concentrations in seaweed tissues, and how these changes affect herbivore feeding behavior, remains poorly understood. We addressed these questions by hypothesizing that physicochemical conditions associated with upwelling increase the concentration of essential biomolecules in seaweed tissues, indirectly modulating herbivore behavior. We first characterized multiple upwelling (UW) and downwelling (DW) sites and used UW–DW field transplants to examine variation in biomolecule concentrations and growth of the widespread southwestern Pacific seaweed Lessonia spicata. We then assessed how seaweed origin influenced the feeding behavior of two common sea urchins, Loxechinus albus and Tetrapygus niger. Seaweeds from UW sites contained higher protein and carbohydrate concentrations than those from DW sites, consistent with higher nutritional quality under natural UW conditions. However, after prolonged exposure to a common DW environment, biomolecule concentrations of UW-origin seaweeds converged toward those of DW-origin individuals. Blade length increased throughout the transplant experiment, but growth rate over the complete experimental period did not differ between origins. Seaweeds from UW sites were consumed at higher rates than those from DW sites, while the feeding responses of both sea urchin species depended on seaweed origin, consumer origin, and species identity. Together, these results indicate that upwelling-associated environmental conditions influence seaweed nutritional traits and consumer-seaweed interactions, while the convergence observed after transplantation highlights the plasticity of these traits under changing local conditions. These findings have implications for predicting ecological responses to future changes in coastal upwelling regimes.
Understanding how top-down and bottom-up forces shape post-disturbance succession across environmental stress gradients remains a central challenge in ecology. Salt marshes are dynamic coastal ecosystems where disturbances, such as wrack deposition, play a key role in regulating plant community structure and diversity, yet the combined effects of herbivory and nutrient availability on post-disturbance recovery in these systems remain poorly understood. We conducted a two-year field experiment nested in a long-term fertilization framework in a Southwestern Atlantic salt marsh to evaluate how herbivore pressure and chronic nitrogen enrichment modulate successional trajectories after wrack disturbance in low- and high-marsh zones. Recovery trajectories differed sharply between marsh elevations. In the low marsh, vegetation recovery was extremely limited despite herbivore exclusion and chronic nitrogen enrichment. In contrast, recovery in the high marsh was rapid and strongly shaped by herbivory and chronic nutrient enrichment. In the high marsh, herbivore exclusion combined with nutrient enrichment promoted rapid convergence towards reference undisturbed communities. Conversely, herbivory or nutrient limitation allowed for more variable community composition. Our results indicate that abiotic stress sets fundamental limits on recovery at low elevations, whereas in more benign environments, the interplay of top-down and bottom-up forces governs both the rate and the predictability of successional trajectories. Abiotic conditions may thus determine whether these forces shape succession at all, rather than only how strongly they do so, with implications for recovery under global change.
Whereas acute stress responses support immediate escape from transient threats, persistent or repeated predation risk (hereafter referred to as chronic predation risk) requires organisms to continually reallocate limited energetic resources among competing physiological demands. Classical stress physiology emphasizes acute “fight-or-flight” responses that transiently mobilize glucose and lipids to skeletal muscle, whereas life‑history and allostatic‑load frameworks highlight long‑term trade-offs between survival, growth, and reproduction. Yet these perspectives rarely specify how energy is redistributed among tissues under persistent threat. Here, we synthesize life-history theory, stress physiology, evolutionary medicine, and recent experimental work in a predator-exposed Drosophila melanogaster model to propose Threat-Induced Neural Prioritization (TINP), a conceptual framework describing how persistent predation risk induces tissue-specific metabolic reorganization that preferentially allocates energetic resources to neural and glial tissues. This reprogramming supports energetically costly processes such as memory consolidation and decision‑making that enhance survival, but reduces investment in peripheral homeostasis and can shade into pathology under environmental mismatch. We outline testable predictions about tissue‑specific substrate use, developmental timing, and taxonomic generality of TINP, and argue that explicitly treating cognition as a life‑history trait clarifies how chronic ecological threats shape both metabolic organization and evolutionary trajectories.
