Microgeographical variation in thermal preference by an amphibian

Abstract

Ectotherms use behaviour to buffer effects of temperature on growth, development and survival. While behavioural thermoregulation is widely reported, localized adaptation of thermal preference is poorly documented. Larval amphibians live in wetlands ranging from entirely open to heavily shaded by vegetation. We hypothesized that populations undergo localized selection leading to countergradient patterns of thermal preference behaviour. Specifically, we predicted that wood frog (Rana sylvatica) larvae from closed canopy ponds would be more strongly temperature selective and would prefer higher temperatures than conspecifics from populations found in open canopy ponds. In a study of six breeding ponds in north-eastern Connecticut, USA, these predictions were upheld. The countergradient, microgeographical variation in thermal preference documented here implies that wood frog populations may have diverged rapidly in the face of contrasting selection pressures. Rapid, behaviourally mediated responses to changing thermal environments have important implications for understanding population responses to climate change.

Plasticity in thermal tolerance has limited potential to buffer ectotherms from global warming

“…Similar processes can also occur in freshwater systems (e.g. [47]). Behavioural thermoregulation thus has the ability both to reduce variability in maximum body temperature and to prevent organisms from experiencing damaging extremes [48,49].…”

Evaluation of temperature-selection differences among juvenile muskellunge originating from different latitudes

“…Local temperature adaptation predicts that the temperatures for optimum growth and energetic processes are adapted to the local temperature conditions and are directly (Levinton 1983;Yamahira and Conover 2002). Alternatively, countergradient variation focuses on differences in the length of the growing season across latitudes and predicts that individuals from cooler environments should select similar or warmer temperatures than conspecifics from warmer environments when presented with a temperature gradient (Conover and Schultz 1995;Freidenburg and Skelly 2004;Belk et al 2005). Selection of warmer temperatures would increase growth rates and, ultimately, result in a large body at the beginning of a long winter (Conover and Present 1990).…”

“…As a result, local populations have different physiological and behavioral responses to their environment; these gradually become adaptive genetic differences among stocks (Ihssen et al 1981;Philipp et al 1993). Local adaptation suggests the possibility of different temperature optima, and thus preferred temperatures (Beitinger and Fitzpatrick 1979;McCauley and Casselman 1981), among populations (Hall et al 1978;Koppelman et al 1988;Angilletta et al 2002;Freidenburg and Skelly 2004).…”

“…Most macrohabitats are thermally heterogeneous and behavior, morphology, and physiology interact to determine the realized body temperature (Tracy 1982;Huey 1991). Behavioral thermoregulation places an organism in temperatures that optimize physiological processes and buffer any negative effects of temperature (Hernandez et al 2002;Freidenburg and Skelly 2004).…”

Oddities and Curiosities in the Algal World

“…It is well know that organisms reaching their critical thermal maximum (CTM, the minimal high deep-body temperature that is lethal to an animal) are incapable of escaping the lethal conditions (Freidenburg and Skelly, 2004). This holds especially true for aquatic organisms in thermally uniform systems, which have no refuge from heat stress; further, temperature increases within such systems decreases the concentration of the necessary gases oxygen and carbon dioxide, (Wu and Kam, 2005).…”