Author: Jean-François Le Galliard

Étude comparative de la démographie de populations de Vipère d’Orsini

Encadrement par Thomas Tully dans notre laboratoire

Le stage consistera à exploiter et analyser les données CMR issues des différentes populations de vipères d’Orsini de la région PACA afin de réaliser une étude comparative des traits morphologiques, démographiques et écologiques entre les différentes populations. Les traits comparés incluront la morphologie et la reproduction mais aussi des estimations de structure de population et de survie. Les compétences qui seront mobilisées incluront la biodémographie, l’écologie des reptiles et les biostatistiques. Des compétences relationnelles seront également indispensables pour collaborer efficacement avec les partenaires du PNA. Ce stage sera enrichi par une participation à une session de suivi sur le terrain au printemps 2025, permettant d’étudier l’une des populations en milieu naturel. Ces interactions sur le terrain offriront l’occasion de découvrir l’articulation entre recherche scientifique fondamentale et actions de conservation appliquées dans le cadre du programme LIFE, dans un territoire où évoluent de nombreux acteurs.

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 !

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. https://doi.org/10.1242/jeb.246129

And the Inside JEB summary: https://doi.org/10.1242/jeb.246568

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!

Contact: ecoleanaee2023@sciencesconf.org
Website: https://anaeeschool2023.sciencesconf.org/

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.

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. https://doi.org/10.1093/biolinnean/blac114

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.

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

We have provided you with a new web page describing our AQUATHERM project funded by Agence Nationale de Recherche and addressing the potential of hydroregulation and thermoregulation to influence ecological responses to climate change in terrestrial ectotherms. Regular updates about this project will be posted on our website.

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

https://onlinelibrary.wiley.com/doi/abs/10.1111/geb.13355