Showing papers by "Jean Clobert published in 2022"

Diverse aging rates in ectothermic tetrapods provide insights for the evolution of aging and longevity

Abstract: 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 populations (77 species) of nonavian reptiles and amphibians. We test hypotheses of how thermoregulatory mode, environmental temperature, protective phenotypes, and pace of life history contribute to demographic aging. Controlling for phylogeny and body size, ectotherms display a higher diversity of aging rates compared with endotherms and include phylogenetically widespread evidence of negligible aging. Protective phenotypes and life-history strategies further explain macroevolutionary patterns of aging. Analyzing ectothermic tetrapods in a comparative context enhances our understanding of the evolution of aging. Description How to cheat senescence? Compared with birds and mammals, herpetiles, especially turtles and tortoises, are well-known examples of extremely long-lived animals that show little evidence of age-related decline (see the Perspective by Austad and Finch). By comparing aging rates and longevity across 77 species of reptiles and amphibians, Reinke et al. found considerable variation in senescence and elucidated some of the drivers of these differences in nature. In another paper, Da Silva et al. studied turtles and tortoises in zoos and found clear evidence that negligible senescence occurs under controlled conditions. —SNV In the wild, the aging rates of reptiles and amphibians range from negligible to fast depending on protective traits and pace of lifestyle.

Lizards from warm and declining populations are born with extremely short telomeres

Abstract: Significance This study unraveled the impacts of accelerated aging as a corollary of climate-driven population decline. We found a transgenerational accumulation of telomere shortening implying that offspring were already born “old.” We suggest that this process may exacerbate across generations, leading to an aging loop in the population. This model posits that telomere dynamics should represent a critical and promising molecular biomarker of population extirpation as well as a way to test the in situ efficiency of conservation decisions.

Environmental conditions and male quality traits simultaneously explain variation of multiple colour signals in male lizards

Abstract: Abstract 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 and camouflage. The relationships between colour signals, male quality traits and environmental factors have often been analysed in isolation, but simultaneous analyses are rare. Thus, the response of multiple colour signals to variation in all these factors in an integrative analysis remains to be investigated. Here, we investigated how multiple colour signals relate to their information content, examined the role of T as a potential mediator of these relationships and how environmental factors explain colour signal variation. We performed an integrative study to examine the covariation between three colour signals (melanin‐based black, carotenoid‐based yellow–orange and structural UV), physiological performance, parasitism, T levels and environmental factors (microclimate, forest cover) in male common lizards Zootoca vivipara from 13 populations. We found that the three colour signals conveyed information on different aspects of male condition, supporting a multiple message hypothesis. T influenced only parasitism, suggesting that T does not directly mediate the relationships between colour signals and their information content. Moreover, colour signals became more saturated in forested habitats, suggesting an adaptation to degraded light conditions, and became generally brighter in mesic conditions, in contradiction with the thermal melanism hypothesis. We show that distinct individual quality traits and environmental factors simultaneously explain variations of multiple colour signals with different production modes. Our study therefore highlights the complexity of colour signal evolution, involving various sets of selective pressures acting at the same time, but in different ways depending on colour production mechanism.

Reproducing in a changing world: combined effects of thermal conditions by day and night and of water constraints during pregnancy in a cold‐adapted ectotherm

Abstract: 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 climate-related environmental conditions, we manipulated day and night temperatures as well as water availability during gestation in female common lizards Zootoca vivipara, a cold and wet adapted species facing climatic changes notably in populations located on the warm margin. We jointly manipulated temperature (hot or cold) independently during the daytime and nighttime as well as water availability (± ad libitum access to water) throughout pregnancy and quantified the effects on maternal traits (morphology, physiology and phenology) and reproductive output. Overall, we found that higher day or night temperatures decreased gestation length and increased energetic demands. Higher temperatures during the day, coupled with water restrictions, increased dehydration and water restrictions affected ability to allocate resources but had no impact on reproductive output. While high temperatures during the day were beneficial to current reproductive output and success, high temperatures during the night had the opposite effect. Our results suggest that high nighttime temperatures can dramatically increase the burden on pregnant mothers already constrained by heavy resource and water investment. This could provide a mechanistic explanation for the long-term declines of warm-margin populations in this species.

Climate aridity and habitat drive geographical variation in morphology and thermo-hydroregulation strategies of a widespread lizard species

Abstract: 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-hydroregulation strategies, but we lack studies that examine these changes across climatic gradients in different habitat types. Here, we investigated intraspecific 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 specific 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.