Can respiratory physiology predict thermal niches?

Temperature is an important factor determining distribution and abundance of organisms. Predicting the impact of warming climate on ectotherm populations requires information about species' thermal requirements, i.e. their so-called 'thermal niche'. The characterization of thermal niche remains a complicated task. We compared the applicability of two indirect approaches, based on reaction norm (aerobic scope curve) and optimality (preferred body temperature) concepts, for indirect estimation of thermal niche while using newts, Ichthyosaura alpestris, as a study system. If the two approaches are linked, then digesting newts should keep their body temperatures close to values maximizing aerobic scope for digestion. After feeding, newts maintained their body temperatures within a narrower range than did hungry individuals. The range of preferred body temperatures was well below the temperature maximizing aerobic scope for digestion. Optimal temperatures for factorial aerobic scope fell within the preferred body temperature range of digesting individuals. We conclude that digesting newts prefer body temperatures that are optimal for the maximum aerobic performance but relative to the maintenance costs. What might be termed the 'economic' thermoregulatory response explains the mismatch between thermal physiology and behaviour in this system.

Section: Discussionmentioning

confidence: 99%

Economic thermoregulatory response explains mismatch between thermal physiology and behavior in newts

Gvoždı́k

Kristín

2017

“…Finally, we tested the OCLTT hypothesis for the mechanism setting thermal limits in our T. elegans populations (hypothesis 3). If thermal tolerance results from oxygen limitation, we predict that oxygen consumption rate will plateau at near-critical high temperatures, plasma glucose concentration will drop, and lactate concentration will increase (Frederich and Pörtner, 2000;Verberk et al, 2016). In quantifying both the hormonal effects on energy mobilization and the whole-organism metabolic response across a range of high temperatures, this study provides insight into the impact of acute exposure to high temperatures on the regulation of homeostasis and energy stores.…”

Section: Introductionmentioning

confidence: 99%

Hormonal and metabolic responses to upper temperature extremes in divergent life-history ecotypes of a garter snake

Gangloff

Holden

Telemeco

et al. 2016

Extreme temperatures constrain organismal physiology and impose both acute and chronic effects. Additionally, temperature-induced hormone-mediated stress response pathways and energetic tradeoffs are important drivers of life-history variation. This study employs an integrative approach to quantify acute physiological responses to high temperatures in divergent life-history ecotypes of the western terrestrial garter snake (Thamnophis elegans). Using wild-caught animals, we measured oxygen consumption rate and physiological markers of hormonal stress response, energy availability and anaerobic respiration in blood plasma across five ecologically relevant temperatures (24, 28, 32, 35 and 38°C; 3 h exposure). Corticosterone, insulin and glucose concentrations all increased with temperature, but with different thermal response curves, suggesting that high temperatures differently affect energy-regulation pathways. Additionally, oxygen consumption rate increased without plateau and lactate concentration did not increase with temperature, challenging the recent hypothesis that oxygen limitation sets upper thermal tolerance limits. Finally, animals had similar physiological thermal responses to high-temperature exposure regardless of genetic background, suggesting that local adaptation has not resulted in fixed differences between ecotypes. Together, these results identify some of the mechanisms by which higher temperatures alter hormonal-mediated energy balance in reptiles and potential limits to the flexibility of this response.

“…In particular, many studies have investigated species' tolerance thresholds to forecast their vulnerability to climate change and to formulate projections that range from individual to community levels (e.g. Helmuth and Hofmann, 2001;Stillman, 2002Stillman, , 2003Bartolini et al, 2013;Magozzi and Calosi, 2015;Verberk et al, 2015). Thus, it is not surprising that the recurrent terms adopted to describe the survival expectancy of intertidal organisms facing climate change are 'stress' and 'risk' (see Helmuth and Hofmann, 2001;Helmuth et al, 2002;Mislan et al, 2009;Denny et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

“…Understanding the thermal responses of ectothermic species is of increasing importance in the light of global warming, especially when considering the effect of climate shifts and instability on the realised thermal niche of species (Etterson and Shaw, 2001;Helmuth et al, 2002;Pörtner, 2002;Pörtner and Knust, 2007;Chown et al, 2010;Bozinovic et al, 2011;Chapperon and Seuront, 2011;Rezende et al, 2011;Anttila et al, 2014;Palumbi et al, 2014;Verberk et al, 2015). The suite of thermal responses utilised by a species, which can entail complex, integrated processes at wholeorganism, cellular and molecular levels, determines their sensitivity to climatic influences and represents the central mechanism for species' thermal adaptation (Pörtner, 2002(Pörtner, , 2010Kassahn et al, 2009;Marshall et al, 2010;Bartolini et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

The importance of thermal history: costs and benefits of heat exposure in a tropical, rocky shore oyster

Giomi

Mandaglio

Ganmanee

et al. 2016

Self Cite

Although thermal performance is widely recognised to be pivotal in determining species' distributions, assessment of this performance is often based on laboratory-acclimated individuals, neglecting their proximate thermal history. The thermal history of a species sums the evolutionary history and, importantly, the thermal events recently experienced by individuals, including short-term acclimation to environmental variations. Thermal history is perhaps of greatest importance for species inhabiting thermally challenging environments and therefore assumed to be living close to their thermal limits, such as in the tropics. To test the importance of thermal history, the responses of the tropical oyster Isognomon nucleus to short-term differences in thermal environments were investigated. Critical and lethal temperatures and oxygen consumption were improved in oysters that previously experienced elevated air temperatures, and were associated with an enhanced heat shock response, indicating that recent thermal history affects physiological performance as well as inducing short-term acclimation to acute conditions. These responses were, however, associated with tradeoffs in feeding activity, with oysters that experienced elevated temperatures showing reduced energy gain. Recent thermal history, therefore, seems to rapidly invoke physiological mechanisms that enhance survival of short-term thermal challenge but also longer term climatic changes and consequently needs to be incorporated into assessments of species' thermal performances.