Jean-François Le Galliard

Ecole Normale Supérieure de Paris | ENS · Centre de Recherche en écologie Expérimentale et Prédictive

To cope with limited availability of drinking water in their environment, terrestrial animals have developed numerous behavioral and physiological strategies including maintaining an optimal hydration state through dietary water intake. Recent studies performed in snakes, which are generalist carnivorous reptiles, suggest that benefits of dietary w...

Optimal regulation of body temperature and water balance is essential for the survival of terrestrial ectotherms in a changing world. A behavioural trade-off exists between these two constraints because maintaining a high body temperature usually increases evaporative water losses. In addition, the evaluation of predation risk is a key factor in be...

During extreme climate events, behavioural thermoregulation may buffer ectotherms from thermal stress and overheating. However, heatwaves are also combined with dry spells and limited water availability, and how much individuals can behaviourally mitigate dehydration risks through microclimate selection remains largely unknown. Herein, we investiga...

Thermo-hydroregulation strategies involve concurrent changes in functional traits related to energy, water balance and thermoregulation and play a key role in determining life-history traits and population demography of terrestrial ectotherms. Local thermal and hydric conditions should be important drivers of the geographical variation of thermo-hy...

Climate change will continue to increase mean global temperatures with daily minima increasing more than daily maxima temperatures. Altered rainfall patterns due to climate change will also disrupt water availability for terrestrial organisms already facing climatic warming. To explore how organisms may adjust to changes in multiple, concurrent cli...

Stress hormones and their impacts on whole organism metabolic rates are usually considered as appropriate proxies for animal energy budget that is the foundation of numerous concepts and models aiming at predicting individual and population responses to environmental stress. However, the dynamics of energy re-allocation under stress make the link b...

Aging is the price to pay for acquiring and processing energy through cellular activity and life history productivity. Climate warming can exacerbate the inherent pace of aging, as illustrated by a faster erosion of protective telomere DNA sequences. This biomarker integrates individual pace of life and parental effects through the germline, but wh...

Male lizards often display multiple pigment‐based and structural colour signals which may reflect various quality traits (e.g. performance, parasitism), with testosterone (T) often mediating these relationships. Furthermore, environmental conditions can explain colour signal variation by affecting processes such as signal efficacy, thermoregulation...

Comparative studies of mortality in the wild are necessary to understand the evolution of aging; yet, ectothermic tetrapods are underrepresented in this comparative landscape, despite their suitability for testing evolutionary hypotheses. We present a study of aging rates and longevity across wild tetrapod ectotherms, using data from 107 population...

Heatwaves and droughts are becoming more intense and frequent with climate change. These extreme weather events often occur simultaneously and may alter organismal physiology, yet their combined impacts remain largely unknown. Here, we experimentally investigated physiological responses of a temperate ectotherm, the asp viper (Vipera aspis), to a s...

Le changement climatique conduit à des modifications graduelles des conditions thermiques et hydriques mais aussi favorise des évènements extrêmes plus intenses et plus fréquents. Alors que les effets des changements de température sur les organismes ectothermes sont classiquement étudiés, les effets combinés des stress thermiques et hydriques extr...

Developmental plasticity and thermal acclimation can contribute to adaptive responses to climate change by altering functional traits related to energy and water balance regulation. How plasticity interacts with physiological syndromes through lifetime in long‐lived species is currently unknown. Here, we examined the impacts of long‐term thermal ac...

Droughts are becoming more intense and frequent with climate change. These extreme weather events can lead to mass mortality and reproduction failure, and therefore cause population declines. Understanding how the reproductive physiology of organisms is affected by water shortages will help clarify whether females can adjust their reproductive stra...

Motivation The understanding of physiological adaptations, of evolutionary radiations and of ecological responses to global change urges for global, comprehensive databases of the functional traits of extant organisms. The ability to maintain an adequate water balance is a critical functional property influencing the resilience of animal species to...

According to animal signalling theory, social costs incurred by aggressive conspecifics are one mechanism maintaining signal honesty. Although our understanding of signal evolution has much improved for pigment-based colours, the mechanisms maintaining the honesty of structural colour signals, such as ultraviolet (UV), remain elusive. Here, we used...

In the past decades, nocturnal temperatures have been playing a disproportionate role in the global warming of the planet. Yet, they remain a neglected factor in studies assessing the impact of global warming on natural populations. Here, we question whether an intense augmentation of nocturnal temperatures is beneficial or deleterious to ectotherm...

Thermoregulation is critical for ectotherms as it allows them to maintain their body temperature close to an optimum for ecological performance. Thermoregulation includes a range of behaviors that aim at regulating body temperature within a range centered around the thermal preference. Thermal preference is typically measured in a thermal gradient...

Ecosystems integrity and services are threatened by anthropogenic global changes. Mitigating and adapting to these changes requires knowledge of ecosystem functioning in the expected novel environments, informed in large part through experimentation and modelling. This paper describes 13 advanced controlled environment facilities for experimental e...

Aim: Determining whether altitudinal shifts in species distributions leave molecular footprints on wild populations along their range margins from rear to leading edge. Location: South-west France. Methods: We compared the demographic and genetic variation in 42 wild populations of the Western oviparous subclade B2 of a cold adapted lizard (Zooto...

Behavioral thermoregulation is an efficient mechanism to buffer the physiological effects of climate change. Thermal ecology studies have traditionally tested how thermal constraints shape thermoregulatory behaviors without accounting for the potential major effects of landscape structure and water availability. Thus, we lack a general understandin...

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One of the greatest current threats to biodiversity is climate change. However, understanding of organismal responses to fluctuations in temperature and water availability is currently lacking, especially during fundamental life-history stages such as reproduction. To further explore how temperature and water availability impact maternal physiology...

While it has long been known that species have contrasted life expectancy (pace of mortality) and generation time (pace of reproduction), recent studies have also uncovered that the shape of adult age trajectories of mortality and reproduction can vary remarkably among species along a continuum of senescence ranging from strong deterioration (senes...

Mechanistic models of terrestrial ectotherms predict that climate warming will induce activity restriction due to heat stress and loss of shade, leading to the extinction of numerous populations. Such models rely on the assumption that activity patterns are dictated by simple temperature thresholds independent of changes in water availability. Howe...

Pre-copulatory female mate choice based on male ultraviolet (UV) coloration has been demonstrated in several vertebrate species; however, post-copulatory mechanisms have been largely overlooked. Here, we investigated female mate preference based on male UV coloration in the common lizard Zootoca vivipara, in which males display conspicuous UV color...

Animals use a variety of strategies to avoid acute dehydration and death. Yet, how chronic exposure to sub-lethal dehydration may entail physiological and fitness costs remains elusive. In this study, we experimentally tested if water restriction causes increased oxidative stress (OS) and telomere length (TL) shortening, two well-described mediator...

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Parent-offspring conflicts are widespread in nature given that resources are often limited. Recent evidence has shown that water can trigger such conflict during pregnancy in viviparous squamate species (lizards and snakes) and thus questions the role of water in the evolution of reproductive modes. Here, we examined the impact of water restriction...

Ecosystem carbon flux partitioning is strongly influenced by poorly constrained soil CO2 efflux (Fsoil). Simple model applications (Arrhenius and Q10) do not account for observed diel hysteresis between Fsoil and soil temperature. How this hysteresis emerges and how it will respond to variation in vegetation or soil moisture remains unknown. We use...

Ecosystem carbon flux partitioning is strongly influenced by poorly constrained soil CO 2 efflux (F soil). Simple model applications (Arrhenius and Q 10) do not account for observed diel hysteresis between F soil and soil temperature. How this hysteresis emerges and how it will respond to variation in vegetation or soil moisture remains unknown. We...

Chronic changes in climate conditions may select for acclimation responses in terrestrial animals living in fluctuating environments, and beneficial acclimation responses may be key to the resilience of these species to global changes. Despite evidence that climate warming induces changes in water availability, acclimation responses to water restri...

Behavioral fight responses to desiccation risk are important to predict the vulnerability of terrestrial animals to climate change and yet, they have received little attention so far. In terrestrial ectotherms, behavioral regulation of the water balance (i.e. hydroregulation) is likely to be plastic and may tradeoff with thermoregulation behavior b...

Reproduction involves considerable reorganization in an organism's physiology that incurs potential toxicity for cells (e.g., oxidative stress) and decrease in fitness. This framework has been the cornerstone of the so‐called ‘oxidative cost of reproduction’, a theory that remains controversial and relatively overlooked in non‐model ectotherms. Her...

Chronic stressors have profound impacts on phenotypes and life history strategies on the short term, but delayed effects of stress experienced late in life remain poorly investigated in wild populations. Here, we used a combined laboratory and field experiment to test if chronic stress late in life has immediate and delayed effects on physiological...

Abstract The regulation of body temperature (thermoregulation) and of water balance (defined here as hydroregulation) are key processes underlying ecological and evolutionary responses to climate fluctuations in wild animal populations. In terrestrial (or semiterrestrial) ectotherms, thermoregulation and hydroregulation closely interact and combine...

Communication via color signals is common in natural systems. Ultraviolet (UV)-blue patches located on the outer-ventral scales of some lacertid lizards are thought to be involved in male-male competition. However, the mechanisms that maintain their honesty remain unknown. Here, we use the common wall lizard Podarcis muralis to test whether the lat...

The evolution of sex determination is complex and yet crucial in our understanding of population stability. In ectotherms, sex determination involves a variety of mechanisms including genetic determination (GSD), environment determination (ESD), but also interactions between the two via sex reversal. In this study, we investigated whether water dep...

The understanding of developmental patterns of body coloration is challenging because of the multicomponent nature of color signals and the multiple selective pressures acting upon them, which further depend on the sex of the bearer and area of display. Pigmentary colors are thought to be strongly involved in sexual selection, while structural colo...

Climate change should lead to massive loss of biodiversity in most taxa, but the detailed physiological mechanisms underlying population extinction remain largely elusive so far. In vertebrates, baseline levels of hormones such as glucocorticoids ( GC s) may be indicators of population state as their secretion to chronic stress can impair survival...

Human activities have altered continental ecosystems worldwide and generated a major environmental crisis, prompting urgent societal questions on how to best produce goods while at the same time securing sustainable ecological services and raising needs to better understand and predict biodiversity and ecosystems dynamics under global changes. To t...

Many scientific disciplines are currently experiencing a 'reproducibility crisis' because numerous scientific findings cannot be repeated consistently. A novel but controversial hypothesis postulates that stringent levels of environmental and biotic standardization in experimental studies reduce reproducibility by amplifying the impacts of laborato...

Behavioral plasticity induced by maternal effects is crucial in adjusting offspring phenotype to match the environment. In particular, changes in water availability during development may initiate a range of behavioral responses, such as natal dispersal, but the contribution of maternal effects from water stress in explaining behavioral variation h...

Identifying the early warning signals of catastrophic extinctions has recently became a central focus for ecologists, but species’ functional responses to environmental changes remain an untapped source for the sharpening of such warning signals. Telomere length (TL) analysis represents a promising molecular tool with which to raise the alarm regar...

Water-conservation strategies are well documented in species living in water-limited environments, but physiological adaptations to water availability in temperate climate environments are still relatively overlooked. Yet, temperate species are facing more frequent and intense droughts as a result of climate change. Here, we examined variation in f...

Parenting is costly and because the relationship between the mother and embryos is not mutualistic, mother–offspring conflicts may exist whenever resource are scarce. However, intergenerational trade‐offs and conflicts resulting from limited access to water, a vital and depreciable resource, remain largely overlooked. In this study, we examined the...

Stress hormones, such as corticosterone, play a crucial role in orchestrating physiological reaction patterns shaping adapted responses to stressful environments. Concepts aiming at predicting individual and population responses to environmental stress typically consider that stress hormones and their effects on metabolic rate provide appropriate p...

The allostatic load model describes how individuals maintain homeostasis in challenging environment and posits that costs induced by a chronic perturbation (i.e., allostatic load) are correlated to the secretion of glucocorticoids, such as corticosterone. Habitat perturbations from anthropogenic activities are multiple and functional responses to t...