Nouveau projet ANR sélectionné !

Nous avons obtenu un nouveau financement du programme générique de l’ANR pour un Projet Collaboratif de Recherche entre notre laboratoire, l’ISYEB du Muséum National d’Histoire Naturelle, EDB à Toulouse, la SETE à Moulis à Toulouse et le CEBC à Chizé pour poursuivre nos travaux de recherche sur l’extinction des populations de lézards. Ce projet TIPEX s’intéressera plus spécifiquement aux points de bascule dans la plasticité du cycle de vie induite par le climat chez un lézard à reproduction bimodale en comparant la sensibilité thermique, les profils de sénescence et la démographie de populations ovipares et vivipares d’un lézard Européen. Démarrage prévu en janvier 2024 !

Does food help lizards restore their water balance ?

In most animals, tight regulation of water balance is critical for short-term survival and chronic disturbance of water balance regulation can further result in loss of performances and ultimately death or sub-optimal reproduction. One way by which animals can recoup water loss from skin evaporation, respiration and feces/urine production is by extracting water from their diet, a phenomenon known as “dietary water intake”. Intuitively, one might expect that animals will search for food, especially high water content diet, when drinking water is limited.Indeed some desert species are able to survive without drinking water by extracting the most water from their diet. Can species living in more temperate climates do the same ?

This is what we were looking for when we designed a clever laboratory experiment with Chloé Chabaud, now post-doctoral student in Tucson, Olivier Lourdais from CNRS Chizé and Georges A. Brusch from California State University at San Marcos. We manipulated food and water availability in the laboratory with adult male common lizards, a species usually found in wet habitats where free standing water is more and more limited to climate change. And contrary to our expectations, prey eating, even from a high quality diet, did not allow lizards to recoup evaporative water loss. Although food intake was critical for body condition maintenance during a chronic water deprivation, plasma osmolality – a marker of physiological dehydration – was similarly high in water deprived lizards with our without food.

Georges A. Brusch

This study adds to a growing number of experiments and field observations suggesting that many carnivorous reptiles have a net dietary water intake rate close to zero either because digestions uses a lot of water or because foraging activities increase water loss rates. This is rarely accounted for in mechanistic models of the energy and water budget of these species, and suggest that many reptiles will be highly dependent on free water drinking when rainfall and moisture conditions are more challenging.

Find out more here: Chabaud , C., Brusch, G. A., Pellerin, A., Lourdais, O. and Le Galliard, J.-F. (2023). Prey consumption does not restore hydration state but mitigates the energetic costs of water deprivation in an insectivorous lizard. J. Exp. Biol. 226 , jeb246129.

And the Inside JEB summary:

Microclimates: physical bases, modelling and characterization in ecology

This 2023 AnaEE France Summer School, organized by myself with 5 specialist teachers from CNRS and INRAE, will take place from September 25 to 29, 2023 at the Jardin du Lautaret as part of the training activities of the national infrastructure AnaEE France. The training is particularly aimed at PhD students, post-doctoral fellows and young researchers wishing to learn and deepen their knowledge on the physical bases, mechanistic and statistical modeling, and the ecological consequences of microclimates. It will consist of a series of lectures to cover theory and concepts, and practical courses with local speakers to conduct field measurement campaigns, analyze data and use modeling tools.

Registration is open until June 30, 2023 – about 25 places available with accommodation and training costs covered!


Geographic variation in thermohydroregulation strategies

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 thermohydroregulation strategies, but we lack studies that examine these changes across climatic gradients in different habitat types. Here, we investigated intraspecifc variation of morphology and thermo-hydroregulation traits in the widespread European common lizard (Zootoca vivipara louislantzi) across a multidimensional environmental gradient involving independent variation in air temperature and rainfall and differences in habitat features (access to free-standing water and forest cover). We sampled adult males for morphology, resting metabolic rate, total and cutaneous evaporative water loss and thermal preferences in 15 populations from the rear to the leading edge of the distribution across an elevational gradient ranging from sea level to 1750 m. Besides a decrease in adult body size with increasing environmental temperatures, we found little effect of thermal conditions on thermo-hydroregulation strategies. In particular, relict lowland populations from the warm rear edge showed no specifc ecophysiological adaptations. Instead, body mass, body condition and resting metabolic rate were positively associated with a rainfall gradient, while forest cover and water access in the habitat throughout the season also influenced cutaneous evaporative water loss. Our study emphasizes the importance of rainfall and habitat features rather than thermal conditions for geographical variation in lizard morphology and physiology.

This project was done in collaboration with CNRS CEBC at Chizé and Cistude Nature with funds from ANR AQUATHERM and Sentinelles du climat program.

Lowland populations in la Forêt des Landes are characterized by hot and dry conditions but shady habitats
Photograph: J.-F. Le Galliard

Chabaud, C., Berroneau, M., Berroneau, M., Dupoué, A., Guillon, M., Viton, R., Gavira, R. S. B., Clobert, J., Lourdais, O., & Le Galliard, J.-F. (2022). Climate aridity and habitat drive geographical variation in morphology and thermo-hydroregulation strategies of a widespread lizard species. Biological Journal of the Linnean Society, blac114.

Les serpents traquent l’humidité de leur environnement

Actualité INEE – 9 janvier 2023

Les épisodes de sécheresse sont de plus en plus fréquents en Europe et accentués lors des canicules estivales à l’image de l’été 2022. La combinaison de fortes chaleurs et du manque d’eau peut avoir de profondes répercussions sur la biodiversité avec des risques de mortalité immédiate. Les reptiles sont animaux « ectothermes » qui régulent leur température en s’exposant plus ou moins aux sources de chaleur par un comportement qu’on dénomme la thermorégulation. Une étude acceptée dans la revue Oecologia démontre pour la première fois que ces organismes choisissent aussi activement les conditions d’humidité de leur habitat par des comportements d’hydrorégulation. Ce travail mené au CNRS de Chizé dans le cadre du projet ANR Aquatherm révèle que ces comportements aident les serpents à limiter les pertes hydriques et donc à atténuer le stress associé aux effets des épisodes de sécheresse. Ces réponses comportementales ne sont possibles que si les milieux naturels sont préservés avec une diversité de microclimats humides.

Vipera aspis
Vipera aspis photographed by Thomas Tully

Behavioural hydroregulation protects against acute effects of drought in a dry-skin ectotherm Mathias Dezetter, Jean François Le Galliard, Olivier Lourdais. Oecologia

Global database of water loss rates for reptiles

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 climate variation. In terrestrial or semi-terrestrial organisms, total water loss includes a significant contribution from evaporative water loss (EWL). The analysis of geographic and phylogenetic variation in EWL rates must however account for differences in methods and potential confounding factors, which influence standard measures of whole-organism water loss. We compiled the global and standardized SquamEWL database of total, respiratory and cutaneous EWL for 325 species and subspecies of squamate reptiles (793 samples and 2,536 estimates) from across the globe. An extensive set of companion data and annotations associated with the EWL measurements of potential value for future investigation, including metabolic rate data, is provided. We present preliminary descriptive statistics for the compiled data, discuss gaps and biases, and identify promising avenues to update, expand and explore this database.

The database can be accessed at a dedicated web site

Fast range expansion in a cold-specialist lizard

In a recent research project coordinated by Jean Clobert and Fabien Aubret at SETE CNRS research station, Andréaz Dupoué sampled tens of common lizard populations (Zootoca vivipara) from the rear edge of the distribution in lowland areas and nearby sea level to the lead edge of the distribution in highland Pyrénées mountain. Sponsored by Ectopyr and Sentinelles du climat grant, this sampling program allowed for the first time a detailed analysis of the genetic footprints of range expansion, habitat fragmentation and climate change in this cold-specialist lizard species found in our mountain range in France. Neutral genetic markers were collected from each sample and their variation was compared between four different ecological units: the rear edge in the Landes forest, an admixture zone and the continuous range in the Pyrénées foothills and the lead edge in highland areas.

Results were strikingly similar to those predicted by a model of genetic structure designed to capture the population history and dynamics from the rear to the lead edge (Hampe and Petit, Ecology Letters 2005). Within the rear edge, we observed the highest levels of inbreeding, genetic differentiation and evidence of interrupted gene flow compared to central or lead edge areas of the distribution. This demonstrates that these relic populations, despite containing a significant genetic diversity globally, are highly fragmented and disconnected, probably as a consequence of climate warming and land use – remember we are in the Landes, a man made highly artificial ecosystem.

Figure 1 - Diversity and distributions

Within the leading edge, altitudinal range expansion high up on the mountains occurred over the last centuries and populations showed relatively low genetic diversity, probably as a consequence of founder effects. The recent range expansion is quite surprising and suggests that these species can disperse over significant distances when local habitat conditions improved.

In general, the demographic and genetic trends were better explained by climate conditions and forest cover. Relative abundance of lizards was smaller in the warm and dry lead edge populations. Inbreeding increased in landscapes less dominated by forests and in warmer climates. Genetic differentiation was higher in colder and more open landscapes. Genetic isolation by distance was relatively obvious but stronger in the leading edge.

These findings suggest unique genetic footprints of range expansion and environmental conditions that should promote the conservation of populations from the rear to the lead edge of the populations if ones would like to save genetic diversity and potential evolvability of this species.

Dupoué, A, Trochet, A, Richard, M, et al. Genetic and demographic trends from rear to leading edge are explained by climate and forest cover in a cold‐adapted ectotherm. Divers Distrib. 2020; 00: 1– 15.