Habitat degradation and hormonal stress: linking physiological theory and conservation biology – DESTRESS

We use experimental approaches combining demographic, hormonal and immunological measures. We will study the functional basis of the response to stress by hormonal manipulation of individuals within closed populations. We analyze the physiological changes, such as metabolism and immune system, bio-indicators of the health of individuals. Finally, our results will be used to generate innovative tools in population viability analysis to test conservation and management strategies.

Experiments have been set up between April and September 2014, the results are being analyzed and recovery.
However a specific project on the influence of stress at the cellular level and more specifically on the metabolism of mitochondria indicate that stress increases the number of mitochondria of individuals, but not their oxygen consumption and efficiency. In addition, chronic stress decreases oxidative damage in contrast to what is predicted. An article is currently being drafted for submission in spring. We also plan to continue this study by examining the dynamics of cellular stress response to see if the short and long term effects are identical or otherwise reverse.

Our project is designed to allow a detailed description of the response of individuals to habitat degradation is consistent with the objectives of the «National Biodiversity Strategy 2011-2020« and the French policy on environmental research. In fact this project led to the common lizard will better understand the impact of environmental change on reptiles. Indeed, numerous studies indicate that populations of reptiles, are currently declining due to habitat loss. Yet studies focusing on the effects of global changes are very often endothermic (birds and mammals), while the majority of animal species are ectothermic. In particular, lizards or snakes have poor dispersal abilities which induces a high sensibility to environmental conditions of these organizations. Our study should allow us to use reptiles as an indicator of health and environmental stability faced with anthropogenic disturbances

in process

A challenge to ecologists, evolutionary and conservation biologists is predicting organismal responses to fast environmental changes and increasing occurrences of extreme events. Evolutionary theory suggests that natural populations of plants and animals inhabiting unpredictable environments should evolve a plastic strategy. But, key questions are how can environmental cues modulate changes in the phenotype and what constraints may limit the potential for plasticity to facilitate coping with changing environments. Immediate strategies for coping with environmental changes must entail physiological plasticity. Therefore, the emerging field of conservation physiology attempts to determine the physiological responses of organisms to environmental changes. In particular, conservation physiology integrates ecology, evolution and physiology to elucidate constraints imposed on the ability of an organism to cope with environmental shifts. Ultimately, information on physiological capacity can be used to predict fitness and population dynamic consequences associated with environmental change and the persistence of species in an altered environment. Yet, the role of physiological plasticity in coping with changing environments remains largely unexplored.
In this proposal, we will use a model vertebrate species, the common lizard (Lacerta vivipara), to understand physiological and demographic effects of habitat degradation. The physiological response to habitat degradation involves a stress response by secretion of glucocorticoids, such as corticosterone, that have strong organizational effects and can generate phenotypic plasticity within and between generations. McEwen and Wingfield’s (2003) proposed a theory, called the allostasis model, to describe how animals maintain homeostasis (i.e., stability) in changing and variable environments by allostasis (i.e. glucocorticoid secretion), which helps predict the shift from compensatory to non-compensatory plastic responses to a stressor. Unfortunately, ecological studies that allow to test the benefits and costs of allostasis in wild populations and make a step forward into more applied conservation problems are rare. Here, we will couple physiological and demographic approaches in order to characterize plastic physiological responses to the degradation of habitat quality via glucocorticoid secretion. First, we will use correlative and manipulative approaches to describe physiological and ecological responses to habitat degradation (task 1) by combining demographic, hormonal and immunological measurements. Secondly, we will investigate the functional basis of the stress response (task 2) by hormonal manipulation of individuals inside enclosed populations. We will analyse associated changes for metabolism, immune system and oxidative stress, which are three potential indicators of the costs of allostasis, and quantify fitness consequences of the hormonal manipulation. Task 2 will shed new lights on proximate mechanisms of the stress response and relevance of physiological responses for fitness. Third, we will investigate the effect of life history stages and environmental contexts on stress response (task 3) by combining hormonal and environmental manipulations. This task will allow us to better understand the modulation of the stress response and the environmental conditions relevant to the emergence of a cost of allostasis. Finally, our combined knowledge will be used to generate innovative tools for population viability analyses (PVA) in order to predicting how populations will respond to change as well as developing and testing conservation strategies and management practices (task 4).This project focuses for the first time on empirical tests of the allostasis model and implications for conservation physiology of terrestrial vertebrates. Our results will provide powerful tools for conservation biologists and also be critical to further advance physiological theory in this field.