Common Lizard Research Articles

Behavioural thermoregulation prevents thermal stress in lizard sperm fertility

Global warming is threatening ectotherms, with strong repercussions on their population dynamics. Body temperature in ectotherm reptiles is crucial to perform all their biological functions, which are maximized within a narrow interval. When faced with new or adverse thermal conditions, reptiles will respond with distributional changes, behavioural adjustments to maintain their internal temperature, or by adapting to the new environment, otherwise, extinctions will occur. Higher temperatures may have negative repercussions, for example, shortening periods of activity, affecting embryo development during gestation or decreasing viability of sperm cells in males. Through behavioural thermoregulation, reptiles can compensate for environmental variations (Bogert effect). Furthermore, according to Janzen’s hypothesis, the physiological cost of responding to adverse thermal conditions will be low in species exposed to higher thermal overlap. Here, we analysed the effect of a change in the thermal regime on sperm cell viability in Sceloporus megalepidurus, a small viviparous lizard from central Mexico. We hypothesized that an active thermoregulator inhabiting temperate mountains is able to prevent the effects of thermal change on sperm cell viability. We found that the change in thermal regime did not modify sperm cell viability, nor does it affect the maturation of sperm cells in the epididymis. Our results support the Bogert effect and suggest that, despite the high temperatures and low thermal quality, S. megalepidurus can maintain its body temperature within an optimal range for sperm cell viability.

Skin morphology of five species of rock lizards of the genus Darevskia (Lacertidae, Squamata)

The microstructure of the tuberculate dorsal and lamellar ventral skin of the body in rock lizards of different ages (Darevskia raddei, D. nairensis, D. valentini, D. dahli, D. armeniaca) has been described for the first time. The thickness of the skin in the most xerophilic species (D. raddei) is less than that in the more hygrophilic species. Rock lizards have single or paired longitudinal skin folds that are not closed from the side, which stretch along the inner side of the scales to its distal edge. Small folds are also present in the lining of the squamous pocket; they consist of all layers of the skin and subcutaneous tissue. A large fold is able to completely block the cavity of the squamous pocket, the volume of which changes with the contraction of the subcutaneous muscle bundles reaching the bases of the scales. Small folds are also present on the scales of tuberous skin. In hygrophilic lizards (Zootoca vivipara), similar formations appear at later stages of postnatal ontogenesis than in rock lizards. The probable functional significance of the described skin structures is discussed.

Parity-specific differences in spatial genetics and dispersal in the common lizard.

Dispersal is a key demographic parameter that plays an important role in determining spatial population dynamic and genetic structure. Linking differences in dispersal patterns to key life-history traits is often confounded by inconsistent environmental pressures experienced by different populations. To explore the link between dispersal and life history, we focus on a site where oviparous and viviparous lineages of the common lizard (Zootoca vivipara) are found adjacent to each other. We take advantage of this shared environment to investigate parity-specific dispersal patterns using high resolution, individual-level spatial genetic autocorrelation and population genomic approaches (11,726 SNPs; 293 oviparous and 310 viviparous individuals). We found isolation-by-distance patterns to be present in both the oviparous and viviparous populations. Density was 2.5 times higher in the viviparous population than the oviparous one, though heterozygosity and genetic diversity measures were similar in the two populations. We found marked differences in the extent of genetic neighbourhoods between the lineages, with the viviparous population showing both dispersal (σ) and spatial genetic autocorrelation (Moran's I) at two-fold greater geographic distances than the oviparous population. We found clear evidence of male-biased dispersal from genetic estimates in the viviparous population. In the oviparous population, evidence of male-biased dispersal is weak or absent. These differences are likely to be closely linked to specific requirements of the alternative reproductive strategies and may be the demographic consequences of mother-offspring interactions. Fine-scale geographic and individual-level measures are key to understanding parity mode differences at microevolutionary scales and to better identifying their ecological and evolutionary impacts.

Viviparity is associated with larger female size and higher sexual size dimorphism in a reproductively bimodal lizard.

Squamate reptiles are central for studying phenotypic correlates of evolutionary transitions from oviparity to viviparity because these transitions are numerous, with many of them being recent. Several models of life-history theory predict that viviparity is associated with increased female size, and thus more female-biased sexual size dimorphism (SSD). Yet, the corresponding empirical evidence is overall weak and inconsistent. The lizard Zootoca vivipara, which occupies a major part of Northern Eurasia and includes four viviparous and two non-sister oviparous lineages, represents an excellent model for testing these predictions. We analysed how sex-specific body size and SSD is associated with parity mode, using body length data for nearly 14,000 adult individuals from 97 geographically distinct populations, which cover almost the entire species' range and represent all six lineages. Our analyses controlled for lineage identity, climatic seasonality (the strongest predictor of geographic body size variation in previous studies of this species) and several aspects of data heterogeneity. Parity mode, lineage and seasonality are significantly associated with female size and SSD; the first two predictors accounted for 14%-26% of the total variation each, while seasonality explained 5%-7%. Viviparous populations exhibited a larger female size than oviparous populations, with no concomitant differences in male size. The variation of male size was overall low and poorly explained by our predictors. Albeit fully expected from theory, the strong female bias of the body size differences between oviparous and viviparous populations found in Z. vivipara is not evident from available data on three other lizard systems of closely related lineages differing in parity mode. We confront this pattern with the data on female reproductive traits in the considered systems and the frequencies of evolutionary changes of parity mode in the corresponding lizard families and speculate why the life-history correlates of live-bearing in Z. vivipara are distinct. Comparing conspecific populations, our study provides the most direct evidence for the predicted effect of parity mode on adult body size but also demonstrates that the revealed pattern may not be general. This might explain why across squamates, viviparity is only weakly associated with larger size.

Breeding phenology drives variation in reproductive output, reproductive costs and offspring fitness in a viviparous ectotherm.

Phenological advances are a widespread response to global warming and can contribute to determine the climate vulnerability of organisms, particularly in ectothermic species which are highly dependent on ambient temperatures to complete their life cycle. Yet, the relative contribution of breeding dates and temperature conditions during gestation on fitness of females and their offspring is poorly documented in reptiles. Here, we exposed females of the common lizard Zootoca vivipara to contrasting thermal scenarios (cold versus hot treatment) during gestation and quantified effects of parturition dates and thermal treatment on life-history traits of females and their offspring for one year. Overall, our results suggest that parturition date has a greater impact than thermal conditions during gestation on life history strategies. In particular, we found positive effects of an earlier parturition date on juvenile survival, growth and recruitment suggesting that environmental dependent selection and/or differences in parental quality between early and late breeders underlie seasonal changes in offspring fitness. Yet, an earlier parturition date compromised the energetic condition of gravid females, which suggests the existence of a mother-offspring conflict regarding the optimisation of parturition dates. While numerous studies focused on the direct effects of alterations in incubation temperatures on reptile life-history traits, our results highlight the importance of considering the role of breeding phenology in assessing the short- and long-term effects of thermal developmental plasticity.

Common lizard primary oviduct cell culture: A model system for the genetic and cellular basis of oviparity and viviparity

Reproduction by egg-laying (oviparity) or live-bearing (viviparity) is a genetically determined trait fundamental to the biology of amniotes. Squamates are an emerging model for the genetics of reproductive mode yet lack cell culture models valuable for exploring molecular mechanisms. Here, we report a novel primary culture model for reproductive biology: cell cultures derived from the oviduct tissues (infundibulum, uterus and vagina) of oviparous and viviparous common lizards (Lacertidae: Zootoca vivipara). We maintained and expanded these cultures for over 100 days, including repeated subculturing and successful revival of cryopreserved cells. Immunocytochemical investigation suggested expression of both epithelial and fibroblast-like proteins, and RNA sequencing of cultured cells as compared to in vivo oviduct tissue showed changes in gene expression in response to the cell culture environment. Despite this, we confirmed the maintenance of distinct gene expression patterns in viviparous and oviparous cells after 60+ days of cell culture, finding 354 differentially expressed genes between viviparous and oviparous cells. Furthermore, we confirmed the expression of 15 viviparity-associated candidate genes in cells maintained for 60+ days in culture. Our study demonstrates the feasibility and utility of oviduct cell culture for molecular analysis of reproductive mode and provides a tool for future genetic experiments.

Higher locomotor costs of pregnancy in viviparous compared to oviparous common lizards (Zootoca vivipara).

Pregnancy is a physiological cost of reproduction for animals that rely on fleeing to avoid predators. Costs of reproduction are predicted to differ between alternative reproductive strategies or modes, such as egg-laying (oviparity) or live-bearing (viviparity). However, disentangling the factors that comprise this cost and how it differs for oviparous or viviparous females is challenging due to myriad environmental, biological, and evolutionary confounds. Here, we tested the hypothesis that costs of pregnancy differ between oviparous and viviparous common lizards (Zootoca vivipara). We predicted that the degree of locomotor impairment during pregnancy and therefore the cost of reproduction would be higher in viviparous females. We conducted our experiment in a hybrid zone containing oviparous and viviparous common lizards. Due to the common environment and inclusion of hybrid individuals, we could infer whether differences were inherent to parity mode. We found that the average and maximum running speed of pregnant females was slower than after they had given birth or laid eggs. Viviparous females experienced an additional pregnancy weight burden and for a longer time period, but were not slower at running than pregnant oviparous females. In addition, we found a parity mode-specific effect of reproductive investment; producing larger clutches was costlier for the locomotor performance of viviparous females for reasons other than the mass increase. Locomotor costs were found to be intermediate in hybrid females, indicating that they are specific to each reproductive mode. Our study shows that viviparous females experience an additional physical and physiological cost of pregnancy and reproductive investment. This two-fold cost implies that viviparous females modulate resource allocation decisions and/or adjust their behavioural responses that result from locomotor impairment.

Patterns of spatial and temporal association between Zootoca vivipara, Anguis fragilis, Vipera berus and Natrix helvetica at artificial refuges

A 15-year data set of reptile observations at corrugated iron refuges was analysed to describe the spatial and temporal associations between species pairs of viviparous lizards Zootoca vivipara, slow worms Anguis fragilis, northern vipers Vipera berus and grass snakes Natrix helvetica. Of the two snake species, only the viper is known as a routine lizard predator. We analysed two variables expressing pairwise reptile associations at refuges. The first analysis was of monthly spatial overlap assessed as the proportion of unique refuge positions used in common, but not necessarily used simultaneously. The second analysis was of a more precise spatial and temporal assessment based on counts of reptile pairs cohabitating at the refuges (i.e. using the same refuges simultaneously). Apart from viviparous lizards paired with either of the two snake species, the frequencies for both variables were either as expected or significantly greater than expected by chance; in particular grass snakes cohabited much more frequently than expected with both vipers (+327%) and slow worms (+218%). In contrast, for the viviparous lizard/viper pair both variables were statistically significantly less frequent than expected by chance - monthly overlap (-35%) and cohabitation (-87%). As viviparous lizards are predated by vipers, cohabiting would be much reduced but the significantly lowered monthly spatial overlap may indicate active avoidance. For the viviparous lizard/grass snake pair the spatial overlap was as expected by chance but, as with vipers, the frequency of cohabiting was significantly less than expected by chance (-75%). These observations are discussed in relation to the known kairomonal responses of this lizard to viper and grass snake deposits. Viper deposits are also believed to act as a kairomone for slow worms, but we found no evidence that they avoided vipers, supporting existing literature showing that V. berus is unlikely to be an important slow worm predator. Keywords: species associations, cohabitation, corrugated iron refuges, viper kairomone, chalk grassland

Integrating behavioural thermoregulatory strategy into the animal personality framework using the common lizard, Zootoca vivipara as a model

The study of consistent between-individual behavioural variation in single (animal personality) and across two or more behavioural traits (behavioural syndrome) is a central topic of behavioural ecology. Besides behavioural type (individual mean behaviour), behavioural predictability (environment-independent within-individual behavioural variation) is now also seen as an important component of individual behavioural strategy. Research focus is still on the ‘Big Five’ traits (activity, exploration, risk-taking, sociability and aggression), but another prime candidate to integrate to the personality framework is behavioural thermoregulation in small-bodied poikilotherms. Here, we found animal personality in thermoregulatory strategy (selected body temperature, voluntary thermal maximum, setpoint range) and ‘classic’ behavioural traits (activity, sheltering, risk-taking) in common lizards (Zootoca vivipara). Individual state did not explain the between-individual variation. There was a positive behavioural type—behavioural predictability correlation in selected body temperature. Besides an activity—risk-taking syndrome, we also found a risk-taking—selected body temperature syndrome. Our results suggest that animal personality and behavioural syndrome are present in common lizards, both including thermoregulatory and ‘classic’ behavioural traits, and selecting high body temperature with high predictability is part of the risk-prone behavioural strategy. We propose that thermoregulatory behaviour should be considered with equal weight to the ‘classic’ traits in animal personality studies of poikilotherms employing active behavioural thermoregulation.

Bacterial pathogens in Ixodes ricinus collected from lizards Lacerta agilis and Zootoca vivipara in urban areas of Wrocław, SW Poland– preliminary study

The aim of this study was to determine the level of infection of Ixodes ricinus ticks with pathogens (Borrelia spp., Rickettsia spp., and Anaplasma spp.) collected from Lacerta agilis and Zootoca vivipara lizards in the urban areas of Wrocław (SW Poland). The study was carried out in July-August 2020. Lizards were caught by a noose attached to a pole or by bare hands, identified by species, and examined for the presence of ticks. Each lizard was then released at the site of capture. Ticks were removed with tweezers, identified by species using keys, and molecular tests were performed for the presence of pathogens. From 28 lizards (17 specimens of Z. vivipara and 11 specimens of L. agilis) a total of 445 ticks, including 321 larvae and 124 nymphs, identified as I. ricinus were collected. A larger number of ticks were obtained from L. agilis compared to Z. vivipara. Molecular tests for the presence of pathogens were performed on 445 specimens of I. ricinus. The nested PCR method for the fla gene allowed the detection of Borrelia spp. in 9.4% of ticks, and it was higher in ticks from L. agilis (12.0%) than from Z. vivipara (1.0%). The RFLP method showed the presence of three species, including two belonging to the B. burgdorferi s.l. complex (B. lusitaniae and B. afzelii), and B. miyamotoi. The overall level of infection of Rickettsia spp. was 19.3%, including 27.2% in ticks collected from Z. vivipara and 17.0% from L. agilis. Sequencing of randomly selected samples confirmed the presence of R. helvetica. DNA of Anaplasma spp. was detected only in one pool of larvae collected from L. agilis, and sample sequencing confirmed the presence of (A) phagocytophilum. The research results indicate the important role of lizards as hosts of ticks and their role in maintaining pathogens in the environment including urban agglomeration as evidenced by the first recorded presence of (B) miyamotoi and (A) phagocytophilum in I. ricinus ticks collected from L. agilis. However, confirmation of the role of sand lizards in maintaining (B) miyamotoi and A. phagocytophilum requires more studies and sampling of lizard tissue.

Influences of ski-runs, meadow management and climate on the occupancy of reptiles and amphibians in a high-altitude environment of Italy.

Alpine ecosystems harbour a rich and highly specialised biodiversity, which is particularly susceptible to anthropogenic disturbances such as habitat loss and fragmentation as well as to climate change. Combined with other forms of land-use conversion, construction and maintenance of ski resorts can have severe consequences on alpine biodiversity. In this study, we show how one amphibian and two reptile species, namely Rana temporaria, Zootoca vivipara and Vipera berus, respond to such impacts by means of a multi-season occupancy analysis. We found all three species both in and outside ski-runs, showing that these habitats do not necessarily preclude their occurrence. Contrarily, this is influenced more by microhabitat availability, such as ground vegetation, humid areas and rock cover, rather than by macro-characteristics like elevation or habitat type. Moreover, we found a climatic influence on the year-to-year occupancy change of the species, with activity-month conditions being more relevant than overwintering ones. Our results demonstrate how, in the specific case of reptiles and amphibians, ski resorts do not necessarily limit species' occurrence and that a mild series of management actions might secure the species' persistence in the area.

Warming effects on lizard gut microbiome depend on habitat connectivity.

Climate warming and landscape fragmentation are both factors well known to threaten biodiversity and to generate species responses and adaptation. However, the impact of warming and fragmentation interplay on organismal responses remains largely under-explored, especially when it comes to gut symbionts, which may play a key role in essential host functions and traits by extending its functional and genetic repertoire. Here, we experimentally examined the combined effects of climate warming and habitat connectivity on the gut bacterial communities of the common lizard (Zootoca vivipara) over three years. While the strength of effects varied over the years, we found that a 2°C warmer climate decreases lizard gut microbiome diversity in isolated habitats. However, enabling connectivity among habitats with warmer and cooler climates offset or even reversed warming effects. The warming effects and the association between host dispersal behaviour and microbiome diversity appear to be a potential driver of this interplay. This study suggests that preserving habitat connectivity will play a key role in mitigating climate change impacts, including the diversity of the gut microbiome, and calls for more studies combining multiple anthropogenic stressors when predicting the persistence of species and communities through global changes.

Microhabitat humidity rather than food availability drives thermo‐hydroregulation responses to drought in a lizard

The regulation of energy, water and thermal balance involves integrated processes that should drive ecological responses of ectotherms to climate change. Functional tradeoffs between thermoregulation and hydroregulation are exacerbated during hot or dry spells, but how microhabitat hydric properties and trophic resource availability influence these tradeoffs remains unknown. Here, we investigated the effects of microhabitat humidity and food availability on thermo‐hydroregulation strategies in the ground‐dwelling common lizard Zootoca vivipara during a simulated hot and dry spell event. We exposed lizards to a five‐day long acute water restriction in hot conditions in the laboratory and manipulated hydric quality of the retreat site (wet or dry shelter) as well as food availability (ad libitum food or food deprivation). Water restriction and food deprivation caused physiological responses such as muscle catabolism and mobilization of caudal energy reserves. Lizards also developed behavioural strategies to conserve water or energy via decreased thermoregulation effort, higher shelter use and increased eye closure behaviours through time. These physiological and behavioural changes were importantly buffered by the presence of a wet shelter but not by food availability. A wet retreat site reduced the behavioural conflicts between thermoregulation and hydroregulation, allowed lizards to maintain a better condition and reduced physiological dehydration. Instead, food intake did not play a major role in the regulation of hydration state and increased behavioural conflicts between thermoregulation and hydroregulation. A better consideration of thermo‐hydroregulation behaviours and microhabitat hydric quality is required to address ectotherm responses to future climate change.

Placental ontogeny in the Yucca Night Lizard, Xantusia vigilis.

Squamate placentas support physiological exchange between mothers and embryos. Uterine and embryonic epithelial cells provide sites for transporting mechanisms and extraembryonic membranes provide the scaffolding for embryonic epithelial cells and vascular systems. Diversity in placental structure involves variation in extraembryonic membrane development as well as epithelial cell specializations. Variation in placental ontogeny is known to occur and, although lineage specific patterns have been described, phylogenetic distribution of specific patterns is poorly understood. Xantusia vigilis is a viviparous lizard in a monophyletic clade, Xantusiidae, of predominantly viviparous species. Xantusiidae is one of two viviparous lineages within the clade Scincoidea that provides an important outgroup comparison for Scincidae, which includes the largest number of independent origins of viviparity among Squamata. Previous reports contain brief descriptions of placental structure of X vigilis but the developmental pattern is unknown including relevant details for comparison with skinks. We studied placental ontogeny in X. vigilis to address two hypotheses: (1) the pattern of development of placental architecture is similar to species of Scincidae and, (2) placental epithelial cell specializations are similar to species of Scincidae. The terminal placental stage of X. vigilis is similar to skinks in that it includes a chorioallantoic placenta and an omphaloplacenta. The chorioallantoic placenta is richly vascularized with thin, squamous epithelial cells separating the two vascular systems. This morphology differs from the elaborate epithelial cell specializations as occur in some skink species, but is similar to many species. Epithelial cells of the omphaloplacenta are enlarged, as they are in scincids, yet development of the omphaloplacenta includes a vascular pattern known to occur only in gerrhonotine lizards. Histochemical staining properties of the epithelium of the omphalopleure of the omphaloplacenta indicate the potential for protein transport, a function not previously reported for lizards.

Comparison of haracteristics of the karyotype and meiosis of cryptic forms of the viviparous lizard Zootoca vivipara and species of the closely related genus Takydromus (Squamata: Lacertidae)

Characteristics of the karyotype and early meiosis of two males of the cryptic “western” form of the viviparous lizard (Zootoca vivipara Lichtenstein, 1823) (genus Zootoca Wagler, 1830) with multiple sex chromosomes (female Z1Z2W/Z1Z1Z2Z2 male) were examined. The data obtained were compared with 1) those of the males of the same cryptic form from other locality, with 2) those of the males of other cryptic form also possessing the multiple sex chromosomes and with 3) those of the species of closely related genus Takydromus Daudin, 1802 with simple sex chromosomes, ZW/ZZ. Multiple sex chromosomes may influence meiosis and play a role in isolation. The males of cryptic western form of Z. vivipara studied revealed the karyotype with 36 acrocentric chromosomes (2n=36A). In early meiosis the spreading of synaptonemal complexes (SC) of the bivalents of these males were obtained and analyzed. Eighteen SC were observed, including SC of the Z1Z1 (pair 6) sex chromosomes. Characteristics of SC are compared with the number and the shape of bivalents and chromosomes at the diakinesis and metaphase 11 stages of the meiosis of the males from other population and with those in the other cryptic Russian form of the species. Comparative analysis of two cryptic forms has demonstrated some differences in the morphology of SC Z1Z1 sex chromosomes at the early stages of prophase 1 of meiosis (the late zygotena – the middle pachytene stages). However both the SC of sex chromosomes and SC of all remained chromosomes were fully synapted. All 18 bivalents were regular segregated forming haploid spermatocyte II with18 chromosomes, including two sex chromosomes (n=8, Z1Z2) Thus characteristics of karyotype and early meiosis of the males of western form belonging to different localities are fully coincident with those of Russian cryptic forms of Z. vivipara with multiple sex chromosomes as well. However, these features were differed from those for the species of the closely related genus Takydromus with simple sex chromosome system (ZW) where some disturbances in the course of mitoses and meiosis were observed. The results are in agreement with those suggested previously about the genomic factor(s) stabilizing the meiosis and the maintenance of multiple sex chromosome in the different cryptic forms of complex Z. vivipara.

Using a Handful of Transcriptomes to Detect Sex-Linked Markers and Develop Molecular Sexing Assays in a Species with Homomorphic Sex Chromosomes.

To understand the biology of a species, it is often crucial to be able to differentiate males and females. However, many species lack easily identifiable sexually dimorphic traits. In those that possess sex chromosomes, molecular sexing offers a good alternative, and molecular sexing assays can be developed through the comparison of male and female genomic sequences. However, in many nonmodel species, sex chromosomes are poorly differentiated, and identifying sex-linked sequences and developing sexing assays can be challenging. In this study, we highlight a simple transcriptome-based procedure for the detection of sex-linked markers suitable for the development of sexing assays that circumvents limitations of more commonly used approaches. We apply it to the spotted snow skink Carinascincus ocellatus, a viviparous lizard with homomorphic XY chromosomes that has environmentally induced sex reversal. With transcriptomes from three males and three females alone, we identify thousands of putative Y-linked sequences. We confirm linkage through alignment of assembled transcripts to a distantly related lizard genome and readily design multiple single locus polymerase chain reaction primers to sex C. ocellatus and related species. Our approach also facilitates valuable comparisons of sex determining systems on a broad taxonomic scale.

Inferring current and Last Glacial Maximum distributions are improved by physiology‐relevant climatic variables in cold‐adapted ectotherms

AbstractAimEcological niche‐based models (ENM) frequently rely on bioclimatic variables (BioV) to reconstruct biogeographic scenarios for species evolution, ignoring mechanistic relations. We tested if climatic predictors relevant to species hydric and thermal physiology better proximate distribution patterns and support location of Pleistocene refugia derived from phylogeographic studies.LocationThe Western Palaearctic.TaxonVipera berus and Zootoca vivipara, two cold‐adapted species.MethodsWe used two sets of variables, that is physiologically meaningful climatic variables (PMV) and BioV, in a multi‐algorithm ENM approach, to compare their ability to predict current and Last Glacial Maximum (LGM) species ranges. We estimated current and LGM permafrost extent to address spatially the cold hardiness dissimilarity between both species.ResultsPMV explained more accurately the current distribution of these two cold‐adapted species and identified the importance of summer temperature and solar radiation that constrain activity in cold habitats. PMV also provide a better insight than BioV predictors on LGM distribution. By including notably, the permafrost extent, PMV‐based models gave parsimonious putative arrangement and validity of refugia for each clade and subclade in accordance with phylogeographic data. Northern refugia were also identified from 48 to 52° N for V. berus and from 50 to 54° N for Z. vivipara.Main ConclusionsOur hybrid approach based on PMV generated more realistic predictions for both current (biogeographical validation) and past distributions (phylogeographic validation). By combining constraints during the activity period (summer climatic niche) and those inherent to the wintering period (freeze tolerance), we managed to identify glacial refuges in agreement with phylogeographic hypotheses concerning post‐glacial routes and colonization scenarios.

Genetic basis and expression of ventral colour in polymorphic common lizards.

Colour is an important visual cue that can correlate with sex, behaviour, life history or ecological strategies, and has evolved divergently and convergently across animal lineages. Its genetic basis in non-model organisms is rarely known, but such information is vital for determining the drivers and mechanisms of colour evolution. Leveraging genetic admixture in a rare contact zone between oviparous and viviparous common lizards (Zootoca vivipara), we show that females (N = 558) of the two otherwise morphologically indistinguishable reproductive modes differ in their ventral colouration (from pale to vibrant yellow) and intensity of melanic patterning. We find no association between female colouration and reproductive investment, and no evidence for selection on colour. Using a combination of genetic mapping and transcriptomic evidence, we identified two candidate genes associated with ventral colour differentiation, DGAT2 and PMEL. These are genes known to be involved in carotenoid metabolism and melanin synthesis respectively. Ventral melanic spots were associated with two genomic regions, including a SNP close to protein tyrosine phosphatase (PTP) genes. Using genome re-sequencing data, our results show that fixed coding mutations in the candidate genes cannot account for differences in colouration. Taken together, our findings show that the evolution of ventral colouration and its associations across common lizard lineages is variable. A potential genetic mechanism explaining the flexibility of ventral colouration may be that colouration in common lizards, but also across squamates, is predominantly driven by regulatory genetic variation.

An overview of the Scottish National Adder Survey 2022-24

A study was commissioned by NatureScot to analyse changes in the status of the adder (Vipera berus) and other native reptiles at 16 sites across mainland Scotland, the Isle of Skye and the Isle of Arran over a 30-year period from 1992-93 to 2022-24. In 2022-24, volunteer surveyors revisited sites that were previously surveyed in 1992-93 to identify changes in occupancy. Visual surveys recorded adder, common lizard (Zootoca vivipara), slow-worm (Anguis fragilis), common frog (Rana temporaria), common toad (Bufo bufo), smooth newt (Lissotriton vulgaris), and palmate newt (Lissotriton helveticus). Adders were observed in comparable or even greater numbers at eight sites (seven of the original sites surveyed in 1992-93), but an apparent loss of adders at three of the original sites, and major declines at a previously favourable site on the Scottish Borders are cause for concern. Of the other reptiles, common lizards were the most widespread, recorded at 12 sites; and slow-worms were least often recorded, in low numbers at only four sites, though this could be expected in visual surveys for this cryptic species. This publication reviews the factors most likely to be affecting adders in Scotland, particularly the loss of suitable habitat, the likely historic impact of persecution and the potential effects of disturbance by recreational site users. It highlights the importance of sympathetic habitat management, with a particular focus on maintaining favourable micro-habitats for reptiles.

Ecological responses of squamate reptiles to nocturnal warming.

Nocturnal temperatures are increasing at a pace exceeding diurnal temperatures in most parts of the world. The role of warmer nocturnal temperatures in animal ecology has received scant attention and most studies focus on diurnal or daily descriptors of thermal environments' temporal trends. Yet, available evidence from plant and insect studies suggests that organisms can exhibit contrasting physiological responses to diurnal and nocturnal warming. Limiting studies to diurnal trends can thus result in incomplete and misleading interpretations of the ability of species to cope with global warming. Although they are expected to be impacted by warmer nocturnal temperatures, insufficient data are available regarding the night-time ecology of vertebrate ectotherms. Here, we illustrate the complex effects of nocturnal warming on squamate reptiles, a keystone group of vertebrate ectotherms. Our review includes discussion of diurnal and nocturnal ectotherms, but we mainly focus on diurnal species for which nocturnal warming affects a period dedicated to physiological recovery, and thus may perturb activity patterns and energy balance. We first summarise the physical consequences of nocturnal warming on habitats used by squamate reptiles. Second, we describe how such changes can alter the energy balance of diurnal species. We illustrate this with empirical data from the asp viper (Vipera aspis) and common wall lizard (Podarcis muralis), two diurnal species found throughout western Europe. Third, we make use of a mechanistic approach based on an energy-balance model to draw general conclusions about the effects of nocturnal temperatures. Fourth, we examine how warmer nights may affect squamates over their lifetime, with potential consequences on individual fitness and population dynamics. We review quantitative evidence for such lifetime effects using recent data derived from a range of studies on the European common lizard (Zootoca vivipara). Finally, we consider the broader eco-evolutionary ramifications of nocturnal warming and highlight several research questions that require future attention. Our work emphasises the importance of considering the joint influence of diurnal and nocturnal warming on the responses of vertebrate ectotherms to climate warming.