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

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 whether intra- and intergenerational telomere dynamics underlies population trends remains an open question. Here, we investigated the covariation between life history, telomere length (TL), and extinction risk among three age classes in a cold-adapted ectotherm (Zootoca vivipara) facing warming-induced extirpations in its distribution limits. TL followed the same threshold relationships with population extinction risk at birth, maturity, and adulthood, suggesting intergenerational accumulation of accelerated aging rate in declining populations. In dwindling populations, most neonates inherited already short telomeres, suggesting they were born physiologically old and unlikely to reach recruitment. At adulthood, TL further explained females' reproductive performance, switching from an index of individual quality in stable populations to a biomarker of reproductive costs in those close to extirpation. We compiled these results to propose the aging loop hypothesis and conceptualize how climate-driven telomere shortening in ectotherms may accumulate across generations and generate tipping points before local extirpation.

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

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.

Les lézards mâles arborent souvent plusieurs signaux colorés de nature pigmentaire et structurale qui reflètent de multiples traits de qualité (e.g. performance, parasitisme), et la testostérone (T) joue souvent un rôle de médiateur dans ces relations. En outre, les conditions environnementales peuvent également expliquer les variations des signaux colorés en influençant des aspects tels que l'efficacité des signaux, la thermorégulation ou le camouflage. Les relations entre signaux colorés, traits de qualité individuelle et facteurs environnementaux ont souvent été analysées séparément, mais rarement de manière simultanée. Ainsi, la réponse de ces multiples signaux colorés aux variations de tous ces facteurs reste à explorer dans le contexte d'une étude intégrative. Ici, nous explorons la relation entre ces multiples signaux colorés et leur contenu informatif, nous examinons le rôle de T comme médiateur potentiel de ces relations et nous recherchons si les conditions environnementales expliquent la variation de ces signaux colorés. Nous avons mené une étude intégrative afin d'examiner la covariation entre trois types de signaux colorés (noir produit par la mélanine, jaune-orange produit par les caroténoïdes et UV produit par des éléments structuraux), la performance physiologique, le parasitisme, les niveaux de T et les conditions environnementales (e.g. microclimat, couverture forestière) chez des mâles du lézard vivipare (Zootoca vivipara) provenant de 13 populations. Nos résultats indiquent que les trois signaux colorés transmettent des informations sur différents aspects de la condition des mâles, en accord avec l'hypothèse de « messages multiples ¼. T influence uniquement le parasitisme, suggérant que T n'agit pas en tant que médiateur des relations entre ces signaux colorés et leur contenu informatif. De plus, les signaux colorés sont plus saturés dans les habitats les plus forestiers, ce qui suggère une adaptation à des conditions lumineuses dégradées. Enfin, les signaux colorés sont plus intenses lorsque les conditions sont mésiques, en contradiction avec l'hypothèse du mélanisme thermal. Nous démontrons que différents traits de qualité individuelle et facteurs environnementaux expliquent de manière simultanée les variations de multiples signaux colorés impliquant différents modes de production. Notre étude souligne ainsi la complexité de l'évolution des signaux colorés, qui implique plusieurs types de pressions de sélection agissant en même temps mais dans des directions différentes selon le mode de production.

Population Genomics of Wall Lizards Reflects the Dynamic History of the Mediterranean Basin.

The Mediterranean Basin has experienced extensive change in geology and climate over the past six million years. Yet, the relative importance of key geological events for the distribution and genetic structure of the Mediterranean fauna remains poorly understood. Here, we use population genomic and phylogenomic analyses to establish the evolutionary history and genetic structure of common wall lizards (Podarcis muralis). This species is particularly informative because, in contrast to other Mediterranean lizards, it is widespread across the Iberian, Italian, and Balkan Peninsulas, and in extra-Mediterranean regions. We found strong support for six major lineages within P. muralis, which were largely discordant with the phylogenetic relationship of mitochondrial DNA. The most recent common ancestor of extant P. muralis was likely distributed in the Italian Peninsula, and experienced an "Out-of-Italy" expansion following the Messinian salinity crisis (∼5 Mya), resulting in the differentiation into the extant lineages on the Iberian, Italian, and Balkan Peninsulas. Introgression analysis revealed that both inter- and intraspecific gene flows have been pervasive throughout the evolutionary history of P. muralis. For example, the Southern Italy lineage has a hybrid origin, formed through admixture between the Central Italy lineage and an ancient lineage that was the sister to all other P. muralis. More recent genetic differentiation is associated with the onset of the Quaternary glaciations, which influenced population dynamics and genetic diversity of contemporary lineages. These results demonstrate the pervasive role of Mediterranean geology and climate for the evolutionary history and population genetic structure of extant species.

Intense nocturnal warming alters growth strategies, colouration and parasite load in a diurnal lizard.

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 ectotherms. Physiological performance is influenced by thermal conditions in ectotherms and an increase in temperature by only 2°C is sufficient to induce a disproportionate increase in metabolic expenditure. Warmer nights may expand ectotherms' species thermal niche and open new opportunities for prolonged activities and improve foraging efficiency. However, increased activity may also have deleterious effects on energy balance if exposure to warmer nights reduces resting periods and elevates resting metabolic rate. We assessed whether warmer nights affected an individual's growth, dorsal skin colouration, thermoregulation behaviour, oxidative stress status and parasite load by exposing yearling common lizards (Zootoca vivipara) from four populations to either ambient or high nocturnal temperatures for approximately 5 weeks. Warmer nocturnal temperatures increased the prevalence of ectoparasitic infestation and altered allocation of resources towards structural growth rather than storage. We found no change in markers for oxidative stress. The thermal treatment did not influence thermal preferences, but influenced dorsal skin brightness and luminance, in line with a predicted acclimation response in colder environments to enhance heat gain from solar radiation. Altogether, our results highlight the importance of considering nocturnal warming as an independent factor affecting ectotherms' life history in the context of global climate change. ​.

Short-term change in water availability influences thermoregulation behaviours in a dry-skinned ectotherm.

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. However, changes in water availability may further influence thermoregulation behaviour of ectotherms through dehydration risk perception, changes in water balance or changes in microclimatic conditions. Here, we experimentally assess the interactive effects of thermal conditions and water availability on activity patterns, shade selection and thermoregulation efficiency in a model ectothermic species. Thermoregulation behaviour of adult common lizards Zootoca vivipara was monitored in outdoor mesocosms as we manipulated water availability, providing water as mist in the morning and free-standing water during the daytime. We recorded operative temperatures and micro-meteorological conditions to infer thermal constraints and dehydration risk. Activity and shade selection were better predicted by continuous changes in thermal conditions and dehydration risk, respectively, than by threshold functions. In addition, water supplementation increased activity in males and reduced shade selection in both sexes, most probably as a behavioural response to the perception of a stronger dehydration risk. Water supplementation also influenced the thermal quality of the environment, which in turn altered daily activity patterns and thermoregulation statistics. This demonstrates that dual effects of heat and water stress on activity patterns may lead to stronger activity restriction as a result of climate change than currently predicted.

Contrasts in short- and long-term responses of Mediterranean reptile species to fire and habitat structure.

Changes in habitat structure constitute a major factor explaining responses of reptiles to fire. However, few studies have examined habitat factors that covary with fire-history variables to explain reptile responses. We hypothesise that more complex habitats should support richer reptile communities, and that species-specific relative abundance should be related to particular habitat features. From spring 2012-2014, twenty-five transects were surveyed in the Albera Region (north-east Iberia). The vegetation structure was measured and the extent of habitat types in a 1000-m buffer around each transect calculated. Reptile-community metrics (species richness and reptile abundance) were related to fire history, vegetation structure, and habitat types, using generalized additive models. These metrics correlated with habitat-structure variables but not with fire history. The number of species increased with more complex habitats but decreased with pine-plantation abundance in the 1000-m buffer. We found contrasting responses among reptiles in terms of time since fire and those responses differed according to vegetation variables and habitat types. An unplanned fire in August 2012 provided the opportunity to compare reptile abundance values between pre-fire and the short term (1-2 years) after the fire. Most species exhibited a negative short-term response to the 2012 fire except Tarentola mauritanica, a gecko that inhabits large rocks, as opposed to other ground-dwelling species. In the reptiles studied, contrasting responses to time since fire are consistent with the habitat-accommodation model of succession. These differences are linked to specific microhabitat preferences and suggest that functional traits can be used to predict species-specific responses to fire.

Phylogenetic relationships of Semaphore geckos (Squamata: Sphaerodactylidae: Pristurus) with an assessment of the taxonomy of Pristurus rupestris.

A molecular phylogeny of the sphaerodactylid geckos of the genus Pristurus is inferred based on an alignment of 1845 base pairs (bp) of concatenated mitochondrial (12S) and nuclear (acm4, cmos, rag1 and rag2) genes for 80 individuals, representing 18 of the 23-26 species, and the three subspecies of P. rupestris. The results indicate that P. rupestris is polyphyletic and includes two highly divergent clades: the eastern clade, found in coastal Iran and throughout the Hajar Mountain range in northern Oman and eastern UAE; and the western clade, distributed from central coastal Oman, through Yemen, Saudi Arabia and north to southern Jordan. Inferred haplotype networks for the four nuclear genes show that the eastern and western clades of "P. rupestris" are highly differentiated and do not share any alleles. Moreover, although the two clades are differentiated by a morphological multivariate analysis, no one character or set of characters was found to be diagnostic. Based on the molecular analysis of specimens from the type locality of P. rupestris rupestris, the name P. rupestris is applied to the eastern clade. The name that should apply to the western clade cannot be clarified until morphological and genetic data for "P. rupestris" is available from the vicinity of Bosaso, Somalia, and therefore we refer to it as Pristurus sp. 1. The phylogenetic tree of Pristurus supports the hypothesis that P. celerrimus is sister to all the other species in the analyses and that the Socotra Archipelago was independently colonized a minimum of two times.