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Bioenergetic approaches have been greatly influential for understanding community functioning and stability and predicting effects of environmental changes on biodiversity. These approaches use allometric relationships to establish species' trophic interactions and consumption rates and have been successfully applied to aquatic ecosystems. Terrestrial ecosystems, where body mass is less predictive of plant-consumer interactions, present inherent challenges that these models have yet to meet. Here, we discuss the processes governing terrestrial plant-consumer interactions and develop a bioenergetic framework integrating those processes. Our framework integrates bioenergetics specific to terrestrial plants and their consumers within a food web approach while also considering mutualistic interactions. Such a framework is poised to advance our understanding of terrestrial food webs and to predict their responses to environmental changes.

The article explores the seasonal piscivory behavior of pumpkinseed sunfish in pond ecosystems in Southern Ontario, Canada. The study reveals that pumpkinseed sunfish exhibit extensive seasonal fish consumption in ponds, even in the absence of large predators. The findings suggest that mesopredator fish like pumpkinseed may fill the top predator niche in pond ecosystems, highlighting the importance of considering ponds in ecological research and understanding the impacts of expanding mesopredator species on aquatic food webs. The study emphasizes the need for further research to test the mesopredator release hypothesis and quantify the consequences of meso- and top predator expansion in pond ecosystems. [Extracted from the article]

Most ecological models are based on the assumption that species interact in pairs. Diverse communities, however, can have higher‐order interactions, in which two or more species jointly impact the growth of a third species. A pitfall of the common pairwise approach is that it misses the higher‐order interactions potentially responsible for maintaining natural diversity. Here, we explore the stability properties of systems where higher‐order interactions guarantee that a specified set of abundances is a feasible equilibrium of the dynamics. Even these higher‐order interactions which lead to equilibria do not necessarily produce stable coexistence. Instead, these systems are more likely to be stable when the pairwise interactions are weak or facilitative. Correlations between the pairwise and higher‐order interactions, however, do permit robust coexistence even in diverse systems. Our work not only reveals the challenges in generating stable coexistence through higher‐order interactions but also uncovers interaction patterns that can enable diversity. [ABSTRACT FROM AUTHOR]

Trophic cascades are indirect positive effects of predators on resources via control of intermediate consumers. Larger-bodied predators appear to induce stronger trophic cascades (a greater rebound of resource density toward carrying capacity), but how this happens is unknown because we lack a clear depiction of how the strength of trophic cascades is determined. Using consumer resource models, we first show that the strength of a trophic cascade has an upper limit set by the interaction strength between the basal trophic group and its consumer and that this limit is approached as the interaction strength between the consumer and its predator increases. We then express the strength of a trophic cascade explicitly in terms of predator body size and use two independent parameter sets to calculate how the strength of a trophic cascade depends on predator size. Both parameter sets predict a positive effect of predator size on the strength of a trophic cascade, driven mostly by the body size dependence of the interaction strength between the first two trophic levels. Our results support previous empirical findings and suggest that the loss of larger predators will have greater consequences on trophic control and biomass structure in food webs than the loss of smaller predators.

Changing temperature can substantially shift ecological communities by altering the strength and stability of trophic interactions. Because many ecological rates are constrained by temperature, new approaches are required to understand how simultaneous changes in multiple rates alter the relative performance of species and their trophic interactions. We develop an energetic approach to identify the relationship between biomass fluxes and standing biomass across trophic levels. Our approach links ecological rates and trophic dynamics to measure temperature-dependent changes to the strength of trophic interactions and determine how these changes alter food web stability. It accomplishes this by using biomass as a common energetic currency and isolating three temperature-dependent processes that are common to all consumer-resource interactions: biomass accumulation of the resource, resource consumption and consumer mortality. Using this framework, we clarify when and how temperature alters consumer to resource biomass ratios, equilibrium resilience, consumer variability, extinction risk and transient vs. equilibrium dynamics. Finally, we characterise key asymmetries in species responses to temperature that produce these distinct dynamic behaviours and identify when they are likely to emerge. Overall, our framework provides a mechanistic and more unified understanding of the temperature dependence of trophic dynamics in terms of ecological rates, biomass ratios and stability.

Increases in the frequency, severity and duration of temperature extremes are anticipated in the near future. Although recent work suggests that changes in temperature variation will have disproportionately greater effects on species than changes to the mean, much of climate change research in ecology has focused on the impacts of mean temperature change. Here, we couple fine-grained climate projections (2050-2059) to thermal performance data from 38 ectothermic invertebrate species and contrast projections with those of a simple model. We show that projections based on mean temperature change alone differ substantially from those incorporating changes to the variation, and to the mean and variation in concert. Although most species show increases in performance at greater mean temperatures, the effect of mean and variance change together yields a range of responses, with temperate species at greatest risk of performance declines. Our work highlights the importance of using fine-grained temporal data to incorporate the full extent of temperature variation when assessing and projecting performance.

Piscivorous predators at the apex of aquatic food webs are thought to exhibit foraging behaviours that depend on environmental conditions. Walleye (Sander vitreus), for example, is a freshwater predator that is most active under low light conditions. This study examined walleye resource use and swimming activity across lakes located in northwestern Ontario representing a gradient of water transparency. Muscle glycolytic potential, an index of swimming activity, was estimated by the activity of the enzyme lactate dehydrogenase (LDH). We show that walleye white muscle LDH activity increased with lake water transparency, but that this relationship is not determined by the use of nearshore resources, estimated from [[delta].sup.13]C stable isotope signatures, or by prey abundance. On the other hand, walleye muscle LDH activity decreased with increasing prey size, and prey size was larger in lakes of low water transparency. These results support a positive relationship between water transparency and swimming activity in walleye, with prey size as an important factor contributing to this effect. Les predateurs aquatiques de haut niveau trophique demontrent des comportements alimentaires variables qui dependent des conditions environnementales. Le dore jaune (Sander vitreus), par exemple, est un predateur d'eau douce plus actif dans des conditions de faible luminosite. L'etude examine les ressources alimentaires et l'activite de nage du dore jaune de lacs du nord-ouest de l'Ontario representant un gradient de transparence de l'eau. Le potentiel de glycolyse musculaire, un indice de l'activite de nage, a ete estime a partir de l'activite de la lacticodeshydrogenase (LDH). Les resultats demontrent que l'activite de la LDH dans les muscles blancs du dore augmente avec la transparence de l'eau des lacs, mais que ce rapport n'est pas determine par l'utilisation de ressources littorales, estimee a partir de signatures isotopiques du carbone ([[delta].sup.13]C), ou par l'abondance des proies. Par contre, l'activite de la LDH dans les muscles du dore diminue avec l'augmentation de la taille des proies, et cette derniere est plus grande dans les lacs de faible transparence de l'eau. Ces resultats supportent l'existence d'un lien positif entre la transparence de l'eau et l'activite de nage du dore, et l'interpretation d'une importante contribution de la taille des proies a ce phenomene. [Traduit par la Redaction], Introduction The foraging behaviour of fish predators depends on locomotor and behavioural characteristics of their prey, with antipredator behaviours like schooling and fast swimming of special importance (Christensen and Persson [...]

Organisms occupying high trophic positions in food webs are proposed to exert a stabilizing effect on ecosystems under changing conditions. A possible mechanism underlying this phenomenon is higher mobility of large-bodied predators, which allows broad spatial scale foraging across habitats. If top predators foraging flexibly across habitats display an enhanced capacity for mobility, they should have increased blood circulation requirements compared with other organisms in a food web. Blood circulation capacity can be estimated from the relative size of the heart ventricle, the muscle mass that powers the cardiac pump. We sampled wild teleost fish in a freshwater lake food web to investigate the relationship between relative heart ventricle size and individual measures of trophic position, energy channel use (littoral versus pelagic), and foraging flexibility (coupling) estimated from [sup.15]N and [sup.13]C stable isotope signatures. The results showed that relative ventricle size is associated with increased relative trophic position and decreased use of littoral carbon across species, but not within species, in this system. The foraging flexibility required for coupling was not associated with heart ventricle size. On croit que les organismes occupant les hautes positions trophiques des reseaux alimentaires stabilisent les ecosystemes lors de conditions changeantes. Un mecanisme possible sous-tendant ce phenomene est la mobilite accrue des predateurs de grande taille qui permettrait l'alimentation sur de grands espaces couvrant differents habitats. Si les grands predateurs qui s'alimentent de faqon flexible dans differents habitats ont une mobilite accrue, ils devraient avoir des besoins en circulation sanguine accrus en comparaison avec les autres organismes d'un reseau alimentaire. La capacite de circulation sanguine peut etre estimee par la dimension relative du ventricule cardiaque; la masse musculaire qui propulse la pompe cardiaque. Plusieurs especes de poissons teleosteens ont ete echantillonnees dans un reseau alimentaire lacustre dans le but d'evaluer le rapport entre la dimension relative du ventricule cardiaque et des mesures individuelles de position trophique, de l'usage du canal energetique littoral, et de la flexibilite de l'alimentation estimee a partir du couplage entre les canaux energetiques littoral et pelagique. Ces dernieres variables ont ete estimees a partir de signatures isotopiques de [sup.15]N and [sup.13]C. Les resultats demontrent que la dimension relative du ventricule est associee a une augmentation de la position trophique et a une diminution de l'usage du canal energetique littoral entre les especes, mais pas au sein des populations, dans ce systeme lacustre. La flexibilite d'alimentation necessaire au couplage n'est pas associee a la dimension du ventricule cardiaque., Introduction Food webs are complex biological systems characterized by a hierarchy of organisms exploiting localized resources. It has been proposed that higher-level organisms in food webs, those occupying higher trophic [...]