Distinguishing between active plasticity due to thermal acclimation and passive plasticity due to Q₁₀ effects: Why methodology matters

Abstract

1. Characterizing thermal acclimation is a common goal of eco-physiological studies and has important implications for models of climate change and environmental adaptation. However, quantifying thermal acclimation in biological rate processes is not straightforward because many rates increase with temperature due to the acute effect of thermodynamics on molecular interactions. Disentangling such passive plastic responses from active acclimation responses is critical for describing patterns of thermal acclimation.2. Here, we reviewed published studies and distinguished between different study designs measuring the acute (i.e. passive) and acclimated (i.e. active) effects of temperature on metabolic rate. We then developed a method to quantify and classify acclimation responses by comparing acute and acclimated Q 10 values. Finally, we applied this method using meta-analysis to characterize thermal acclimation in metabolic rates of ectothermic animals.3. We reviewed 258 studies measuring thermal effects on metabolic rates, and found that a majority of these studies (74%) did not allow for quantifying the independent effects of acclimation. Such studies were more common when testing aquatic taxa and continue to be published even in recent years. 4.A meta-analysis of 96 studies where acclimation could be quantified (using 1,072 Q 10 values) revealed that 'partial compensation' was the most common acclimation response (i.e. acclimation tended to offset the passive change in metabolic rate due to acute temperature changes). However, 'no acclimation' and 'inverse compensation', in which acclimation further augmented the acute change in metabolic rate, were also common. 5. Acclimation responses differed among taxa, habitats and with experimental design. Amphibians and other terrestrial taxa tended to show weak acclimation responses, whereas fishes and other aquatic taxa tended to show stronger compensatory responses. Increasing how long the animal was allowed to adjust to a new test temperature increased the acclimation response, but body size did not.Acclimation responses were also stronger with longer acclimation durations.

To us insectometers, it is clear that insect decline in our Costa Rican tropics is real, so let’s be kind to the survivors

“…Insects exhibit strong sensitivity to, and use of, weather cues and intensity (e.g., refs. 17, 18, and 27-34), be they resident or migrants [as expected of tropical species living "normally" in a relatively monotonous and predictable weather and climate regime (35,36)]. All have been variously impacted by the mild to strong disruption of their cue patterns and intensities, and those of the plants and vertebrates with which they mutualize and trophically relate.…”

Temperature dependence of metabolic rate in tropical and temperate aquatic insects: Support for the Climate Variability Hypothesis in mayflies but not stoneflies

“…Given that mayflies were paired by elevations having similar mean environmental and acclimation temperatures, these differences cannot be attributed to the acute or passive response of metabolic rate to higher temperatures alone (Havird et al, 2020).…”

Individual variation in seasonal acclimation by sympatric amphibians: A climate change perspective

“…We quantified the magnitude of seasonal acclimation as the difference between summer and spring trait values for each individual and for each body temperature (Figure 1). Given that the thermal response of SMR and SLA is nonlinear across body temperatures in our study species (Baškiera & Gvoždík, 2019; Gvoždík & Kristín, 2017), we prefer this simple measure over other proposed alternatives based on the ‘semi‐logaritmic thermal dependence’ assumption (Einum et al., 2019; Havird et al., 2020; Seebacher et al., 2015). Seasonal acclimation varies markedly between traits, hence they were scaled to standard deviation units before analysis to allow easy comparison (Araya‐Ajoy et al., 2015).…”