Inaccurate or disparate temperature cues? Seasonal acclimation of terrestrial and aquatic locomotor capacity in newts

Abstract

Summary1. Many organisms respond to seasonal temperature fluctuations by the reversible modification of whole-animal performance. Semiaquatic ectotherms, which possess this acclimatory capacity in swimming speed, lack the plastic response in terrestrial locomotor performance and vice versa. Theory predicts that the presence of reversible (seasonal) thermal acclimation or fixed phenotypes depends on the predictability of future thermal conditions (i.e. accuracy of temperature cues) in a given environment. Alternatively, comparative data suggest that thermal acclimation is induced by disparate temperature cues in water and on land. 2. We tested both predictions by examining the seasonal acclimation response in thermal sensitivity of maximal swimming and running speed in adult alpine newts, Ichthyosaura (formerly Triturus) alpestris. 3. Following the seasonal variation in environmental temperatures, we exposed newts to 5°C from November to March and, after a gradual temperature increase, to either a constant (15°C) or fluctuating (10-20°C) thermal regime from May to June. At the end of each treatment, we measured newt swimming and running capacity at five temperatures (range 5-25°C). In the field, hourly temperatures were recorded in various aquatic and terrestrial microhabitats to obtain information about the predictability of thermal conditions in both environments. 4. Seasonal acclimation shaped the thermal sensitivity of swimming speed under both constant and fluctuating temperature treatments. Thermal sensitivity of running speed was markedly modified by a fluctuating thermal regime so that newts ran at the highest test temperature faster than cold-acclimated individuals. Natural thermal environment contained a similar proportion of predictable variation in water and on land. 5. Complex seasonal acclimation of locomotor capacity in newts was influenced by the disparate thermal cues, i.e. mean acclimation temperature or diel temperature fluctuations, rather than by the different accuracy of these cues in water and on land. Future confrontations of theory with empirical data will require more attention not only on the assumptions of adaptive thermal acclimation but also on the ecologically relevant thermal conditions during acclimation experiments.

Seasonal Acclimation of Preferred Body Temperatures Improves the Opportunity for Thermoregulation in Newts

“…Most studies focused on the modification of the mean value of T p rather than of the T p range, though the position of range limits, not of the mean (relative to a given distribution of operative temperatures [T e ]), affects the thermal habitat quality and accordingly ectotherm's thermoregulatory strategy (Hertz et al 1993). Acclimation studies on T p were often realized under constant temperature treatments (but see Lillywhite 1971;Podrabsky et al 2008), though in ectotherms exposed to diel temperature fluctuations, the acclimatory response is sometimes triggered by diel cycles rather than by the shift in mean body temperature (Šámajová and Gvoždík 2010). In addition, stressful (i.e., constant and/ or too high) acclimation temperatures may induce only the compensatory response of T p (Licht 1968), and thus miss the adaptive significance of T p acclimation under prevailing thermal conditions in the field.…”

Use of Olfactory Cues by Newly Metamorphosed Wood Frogs (Lithobates sylvaticus) during Emigration

“…That is, natal pool cues elicited an attraction behavior from animals held in laboratory conditions, while animals caught in natural conditions were indifferent to such cues. In this context, experiments that minimize laboratory holding period (such as used in our experiment) and use animals raised in natural or seminatural conditions (e.g., mesocosms) are more likely to identify real-world behaviors (Šamajová and Gvoždík, 2010).…”

Aquatic‐to‐terrestrial habitat shift reduces energy expenditure in newts

“…The boom of acclimation studies over the last two decades has substantially improved general knowledge of the reversible plastic responses (reviewed by Whitman, ), however it has also caused a publication bias. Some factors, such as ecologically realistic temperature regimes have been consistently studied (Podrabsky and Somero, ; Šamajová and Gvoždík, ), while other environmental cues remain little understood.…”

“…The boom of acclimation studies over the last two decades has substantially improved general knowledge of the reversible plastic responses (reviewed by Whitman, 2009), however it has also caused a publication bias. Some factors, such as ecologically realistic temperature regimes have been consistently studied (Podrabsky and Somero, 2004;Šamajová and Gvoždík, 2010), while other environmental cues remain little understood.Migrating taxa are subjected not only to passive seasonal variations, but also to behaviorally induced shifts in abiotic conditions. A notable example includes some adult amphibians that regularly change between aquatic and terrestrial lifestyles.…”