2019), but without the ability to reliably detect these stressors the plastic traits would be of only limited advantage. Hence, the ability to plastically modify CORT levels in response to short-term stress can be favoured in spatially and temporally heterogeneous environments (e. However, maintaining high CORT levels over extended periods can come at the cost of reduced growth or delayed development (Denver 2009 Middlemis Maher et al. In the short term, elevated CORT levels can allow rapid energy mobilization to different stress responses (Denver 2009). In amphibians, stressors such as predators activate the neuroendocrine stress axis (hypothalamic–-pituitary–interrenal axis, HPI), with corticosterone (henceforth CORT Denver 2009) as the main hormonal mediator of stress responses. 2010).Īquatic larval stages of many amphibians are well-suited to study plastic and genetic responses to stress as they are sensitive to environmental change, occur in distinct environments and often show strong local adaptation (Beebee 2005). reduced growth, development or reproduction Tollrian and Harvell 1999 Ferrari et al. While such behavioural responses increase the immediate survival chances of the prey, they can have negative long-term consequences (e.g. Plastic alteration of activity level is one of the most prevalent responses, whereby prey typically reduces activity to avoid detection (Lima and Dill 1990 Kats and Dill 1998). Lima and Dill 1990 Tollrian and Harvell 1999 Ferrari et al. To avoid being eaten, prey often alter their behaviour and develop morphologically distinct defense traits (e.g. Predator presence is an ubiquitous biotic stressor in nature. Physiologically stressful conditions, such as extreme temperature or pH, necessitate organismal investment to maintenance of physiological balance, whilst ensuring other key functions, such as resource acquisition and evasion from predators (e.g. However, to what extent populations differ in behavioural and physiological stress responses is poorly understood. reduced activity or increased erratic behaviour) or altered levels of glucocorticoids (cortisol or corticosterone) (reviewed in Gormally and Romero 2020). As many environmental stressors fluctuate strongly in space and time, short-term stress responses can be important components and indicators of reversible phenotypic plasticity (Gabriel 2005), and are often measured as behavioural modifications (e.g. Importantly, environmental stressors typically covary in nature, resulting from simultaneous shifts of abiotic and biotic factors, which can lead to trade-offs in fitness related traits (Folt et al. 2010 Merilä and Hendry 2014 Chevin and Hoffmann 2017 Fox et al. 2007), which can help mitigate effects of environmental stressors (e.g. An alternative, but not mutually exclusive, mechanism for within-generation stress responses arises via phenotypic plasticity (Pigliucci 2001 Ghalambor et al. When different populations inhabit contrasting stress environments, environmental stress can lead to strong divergent natural selection and facilitate local adaptation (Kawecki and Ebert 2004). arvalis is mediated, in part, via behavioural and hormonal plasticity.Įnvironmental stress, defined as any outside influence that reduces organismal performance and fitness, is a powerful evolutionary force (Hoffmann and Parsons 1997 Hoffmann and Hercus 2000). These results suggest that adaptation to environmental acidification in R. ![]() After 8 h exposure, AOP tadpoles had elevated CORT levels in the acid-predator cue treatment and after 24 h exposure they had elevated CORT levels in all three stress treatments (relative to the benign neutral–no-cue treatment). The AOP and NOP tadpoles differed also in their CORT responses, with AOP being more responsive (CORT levels of NOP tadpoles did not differ statistically across treatments). Both AOP and NOP tadpoles reduced their activity in acidic pH, but the response to the predator cue differed between the populations: AOP tadpoles increased whereas NOP tadpoles decreased their activity. We assessed behavioural activity within the first 15 min, and tissue CORT within 8 and 24 h of stress exposure. Tadpoles were initially reared in benign conditions at pH 7 and then exposed to a combination of two pH (acid versus neutral) and two predator cue (predator cue versus no predator cue) treatments. ![]() Here, we compared short-term behavioural (activity) and physiological (corticosterone levels, CORT) responses of Rana arvalis tadpoles from two divergent populations (acid origin, AOP, versus neutral origin, NOP) to acid and predator stress. To cope with stress, organisms can adjust through phenotypic plasticity and/or adapt through genetic change. Environmental stress is a major driver of ecological and evolutionary processes in nature.
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