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Evolutionary ecophysiology of metabolic downstates

Global changes and increasing frequency of unpredictable events appear as major threat for the vast majority of animal kingdom. There is growing interest in how well behavioural and physiological flexibility can buffer organisms from environmental hazards. Key metabolic constraints imposed by environmental fluctuations include a reduction in food availability, changes in food quality, periods of coldness or of dryness.

Organisms have adapted to environmental variability over the course of evolution. Energy conservation allows organisms to optimize their energy allocation to fitness components, i.e. survival, reproduction and growth, according to environmental conditions.

The ability to save energy through behavioral and physiological responses, such as entering a state of hypometabolism possibly associated with hypothermia, and to allocate it into the different fitness components, has great ecological relevance for animal species, and also implies important evolutionary aspects.

To date, the underlying regulatory mechanisms of such strategies are far from being entirely understood, and many aspects still remain to be investigated. So far, the vast majority of research in this area has been done with a focus on small, endothermic animals that have to maintain a high core body temperature but can also enter an hypometabolic state under certain environmental circumstances. More rarely these mechanisms are studied in large endotherms or in ectotherms, in which ambient temperature governs body temperature and metabolism.

Behavioral and hypometabolic responses, however, seem to be present in a large variety of animal species, and appear as a continuum of mechanisms for living at a low pace. Mechanisms of energy savings imply some important evolutionary aspects leading to contrasting strategies of energy management and allocation to different fitness components. In the context of global environmental changes, understanding how the physiological flexibility that enables organisms to cope with fluctuating environments during their lifetime can be continued in species populations, via some inherited mechanisms, constitutes a great avenue of research.

The research conducted in this group aims at understanding the regional and/or whole-body mechanisms of energy savings used by animal species in the context of a constantly changing environment, as well as the ecological and evolutionary implications of such strategies for an individual’s life and for entire animal populations. The focus is on behavioural and hypometabolic responses and thermal tolerance that enable animal species to optimize energy allocation to fitness components. To this aim, we are developing an integrative approach from the whole organism down to cellular or molecular levels to unravel the adaptive mechanisms of small (e.g. hamsters, tamias, dormice) to large (e.g. bears, elephant seals) mammalian heterotherms under laboratory, semi-captive and free-ranging conditions.