Adding Fuel to the “Fire of Life”: Energy Budgets across Levels of Variation in Ectotherms and Endotherms

Careau, Vincent; Killen, Shaun S.; Metcalfe, Neil B.

doi:10.1002/9781118398814.ch14

Cited by 27 publications

(1 citation statement)

References 65 publications

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“…However, a more developed metabolic machinery also entails higher costs spent on self-maintenance, and finite energy, when allocated into one function, can limit other processes (Stearns, 1992). Hence, the 'allocation' hypothesis considers metabolic machinery costly and expects negative fitness-related consequences (Careau et al, 2014;Gadgil & Bossert, 1970;Larivee et al, 2010;Steyermark, 2002). In endothermic animals characterized by the ability to produce heat as a byproduct of energy metabolism, the self-maintenance costs of metabolic machinery correlate with the basal metabolic rate (BMR)the minimum metabolism required for a resting animal to maintain a stable and high body temperature (T b ) under thermoneutral conditions (McNab, 1997;Scholander et al, 1950).…”

Section: Introductionmentioning

confidence: 99%

Predation can shape the cascade interplay between heterothermy, exploration and maintenance metabolism under high food availability

Boratyński,

Iwińska,

Wirowska

et al. 2024

Ecology and Evolution

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Maintenance metabolism as the minimum energy expenditure needed to maintain homeothermy (a high and stable body temperature, Tb), reflects the magnitude of metabolic machinery and the associated costs of self‐maintenance in endotherms (organisms able to produce heat endogenously). Therefore, it can interact with most, if not all, organismal functions, including the behavior–fitness linkage. Many endothermic animals can avoid the costs of maintaining homeothermy and temporally reduce Tb and metabolism by entering heterothermic states like torpor, the most effective energy‐saving strategy. Variations in BMR, behavior, and torpor use are considered to be shaped by food resources, but those conclusions are based on research studying these traits in isolation. We tested the effect of ecological contexts (food availability and predation risk) on the interplay between the maintenance costs of homeothermy, heterothermy, and exploration in a wild mammal—the yellow‐necked mouse. We measured maintenance metabolism as basal metabolic rate (BMR) using respirometry, distance moved (exploration) in the open‐field test, and variation in Tb (heterothermy) during short‐term fasting in animals captured at different locations of known natural food availability and predator presence, and with or without supplementary food resources. We found that in winter, heterothermy and exploration (but not BMR) negatively correlated with natural food availability (determined in autumn). Supplementary feeding increased mouse density, predation risk and finally had a positive effect on heterothermy (but not on BMR or exploration). The path analysis testing plausible causal relationships between the studied traits indicated that elevated predation risk increased heterothermy, which in turn negatively affected exploration, which positively correlated with BMR. Our study indicates that adaptive heterothermy is a compensation strategy for balancing the energy budget in endothermic animals experiencing low natural food availability. This study also suggests that under environmental challenges like increased predation risk, the use of an effective energy‐saving strategy predicts behavioral expression better than self‐maintenance costs under homeothermy.

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Section: Introductionmentioning

confidence: 99%

Predation can shape the cascade interplay between heterothermy, exploration and maintenance metabolism under high food availability

Boratyński,

Iwińska,

Wirowska

et al. 2024

Ecology and Evolution

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Divergence in digestive and metabolic strategies matches habitat differentiation in juvenile salmonids

Monnet

Rosenfeld

Richards

2022

Ecology and Evolution

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Divergent energy acquisition and processing strategies associated with using different microhabitats may allow phenotypes to specialize and coexist at small spatial scales. To understand how ecological specialization affects differentiation in energy acquisition and processing strategies, we examined relationships among digestive physiology, growth, and energetics by performing captive experiments on juveniles of wild coho salmon ( Oncorhynchus kisutch ) and steelhead trout ( O. mykiss ) that exploit adjacent habitats along natural low‐to‐high energy flux gradients (i.e., pools versus riffles) in coastal streams. We predicted that: (i) the specialization of steelhead trout to high‐velocity, high‐energy habitats would result in elevated food intake and growth at the cost of lower growth efficiency relative to coho salmon; (ii) the two species would differentiate along a rate‐maximizing (steelhead trout) versus efficiency‐maximizing (coho salmon) axis of digestive strategies matching their ecological lifestyle; and (iii) the higher postprandial metabolic demand (i.e., specific dynamic action, SDA) associated with elevated food intake would occupy a greater fraction of the steelhead trout aerobic budget. Relative to coho salmon, steelhead trout presented a pattern of faster growth and higher food intake but lower growth efficiency, supporting the existence of a major growth versus growth efficiency trade‐off between species. After accounting for differences in ration size between species, steelhead trout also presented higher SDA than coho salmon, but similar intestinal transit time and lower assimilation efficiency. Both species presented similar aerobic budgets since the elevated SDA of steelhead trout was largely compensated by their higher aerobic scope relative to coho salmon. Our results illustrate the key contribution of digestive physiology to the adaptive differentiation of juvenile growth, energetics, and overall performance of taxa with divergent habitat specializations along a natural productivity gradient.

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Pace of life syndrome under warming and pollution: integrating life history, behavior, and physiology across latitudes

Debecker

Stoks

2018

Ecological Monographs

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To fully comprehend and predict the impact of drivers of global change such as climate warming and pollution, integrated multi‐trait approaches are needed. As organismal traits are often correlated, responses to stressors are expected to induce coordinated changes in many traits. A promising framework to study this is the pace of life syndrome (POLS), which predicts the integration of life history, behavioral, and physiological traits along a fast‐slow continuum. Using an integrative multi‐trait approach, we evaluated the presence of a POLS both within and across latitudes and how POLS patterns are affected by warming and metal pollution. We studied this in Ischnura elegans damselfly larvae of replicated low‐ and high‐latitude populations that strongly differ in voltinism (three to four generations per year vs. one generation every two years) reared in a common‐garden experiment at two temperatures. Across latitudes, life history, behavior, and physiology covaried in accordance with the POLS, with the fast‐paced low‐latitude damselflies characterized by a fast growth rate, high activity, and more explorative and risk‐taking behavior, fast metabolic rate, and low investment in immune function (activity of phenoloxidase). This fast POLS strategy was associated with a higher sensitivity to metal exposure and a higher vulnerability to predation. Warming caused opposite responses between the latitudes consistent with differential thermal adaptation in growth rate, behavior, and oxidative stress parameters. Despite this, damselflies of both latitudes showed a consistent pattern in phenotypic correlations among traits that, moreover, was not affected by warming and metal exposure. Within latitudes, there was no full support for the POLS. More active larvae were more explorative and risk taking, which aligned with the fast‐slow life history axis, but less strong than at the across‐latitude level. Physiological traits were also integrated within latitudes, yet there was no unambiguous coupling with the fast‐slow life history continuum. The consistent syndrome structure, if underpinned by genetic correlations, may restrict the independent evolution of individual traits, yet may not necessarily constrain adaptive evolution of integrated trait sets. This is because the covariance pattern was to a large extent similar across latitudes and within latitudes, suggesting adaptive trait integration guiding adaptive evolution of trait sets along the fast‐slow continuum.

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Adding Fuel to the “Fire of Life”: Energy Budgets across Levels of Variation in Ectotherms and Endotherms

Cited by 27 publications

References 65 publications

Predation can shape the cascade interplay between heterothermy, exploration and maintenance metabolism under high food availability

Predation can shape the cascade interplay between heterothermy, exploration and maintenance metabolism under high food availability

Divergence in digestive and metabolic strategies matches habitat differentiation in juvenile salmonids

Pace of life syndrome under warming and pollution: integrating life history, behavior, and physiology across latitudes

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