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Interspecific aggression has important fitness consequences across the animal kingdom and can be especially important during species invasions, where asymmetric interactions between native and invasive species can lead to native species declines. We investigated the immediate behavioural consequences of interspecific interactions for a native species, the green anole lizard, Anolis carolinensis, after an invasion by a closely related invasive species, the Cuban brown anole, Anolis sagrei. We housed captive populations of green anoles (6 males, 6 females) in large outdoor enclosures and recorded their display behaviours (displays/min), activity levels (movements/min) and habitat use (2D and 3D home range size, perch height) for 10 days. We then introduced brown anoles and recorded the green anoles' behaviours for another 10 days, seeking differences between pre- and post-invasion behaviours. We recorded behavioural interactions between individuals (i.e. headbob and dewlap displays, chases, mating attempts, fights and copulations) throughout the study. To serve as a density control, we duplicated the experiment in a second enclosure using green anoles as ‘invaders’. We performed the experiment eight times with two densities of invaders: high (4 males, 4 females) and low (2 males, 2 females). We found that green anoles have smaller two-dimensional and three-dimensional home ranges and higher average perch heights after invasions but that these changes resulted from increased population densities rather than aggression from brown anole invaders. Furthermore, although green and brown anoles did display to each other, both species preferentially interacted with conspecifics and escalated aggressive behaviours between the two species (e.g. lock-jawed fights) rarely occurred. Taken together, these findings indicate that high brown anole population densities, rather than direct interference competition, could be driving green anole displacement across the brown anole's invasive range.

Behaviour is a highly labile trait that can be rapidly modified to mitigate the effects of changing environmental conditions. Among the biotic and abiotic factors acting to prompt plastic responses, the social environment has been proposed as being one of the primary modulating forces on behaviour. Being part of a group has particular influence on the expression of risky behaviour in that added eyes and ears serve to decrease a group member's vulnerability to predation resulting in the mean behavioural expression of behaviours such as activity and/or exploration increasing with group size. A large body of work has documented such group size effects. However, as this process may operate at the individual level it is unclear how the social environment affects the consistent expression of personality. Thus, we examined the interactive effects of behavioural phenotype and social context on the stability of individual behaviour in the delicate skink, Lampropholis delicata. Lizards were exposed to a series of assays measuring activity, exploration and boldness in groups of one, two, four and eight. Repeatability was determined across group size treatments and the combined effects of social context and behavioural type on behavioural plasticity were assessed. We found that the predicted patterns of group size effects were only observed when each lizard's behavioural phenotype was considered. Inactive and shy lizards increased their behaviour with increasing group size whereas active and bold lizards exhibited the opposite pattern. Additionally, the degree to which an individual adjusted its behavioural response was contingent upon its behavioural phenotype, with slow lizards showing higher levels of responsiveness than fast lizards. Despite this plasticity, between-individual differences in the expression of activity, exploration and boldness persisted. Thus, our study provides strong evidence that the effects of an individual's personality are stronger than those of group size.

Despite growing attention to the ecological and evolutionary importance of consistent individual differences in behaviour (animal personality), long-term field studies quantifying factors associated with behavioural repeatability remain rare. Here, we studied animal personalities over an 8-year period, representing 6 study years, in a wild population of the long-lived sleepy lizard, Tiliqua rugosa. Using Bayesian generalized linear mixed models for 170 unique individuals and a total of 379 lizard-years, we (1) considered the effects of a suite of predictors – particularly lizard sex, mass and tick counts – on lizard aggression and boldness (2) assessed repeatability (i.e. consistent differences among individuals), of these behaviours over different timescales and between lizard sexes and (3) evaluated the correlation, or behavioural syndrome, between aggression and boldness. We found that males were marginally more aggressive and bolder than females, mass had no significant effect and tick loads exhibited a positive relationship with aggression and boldness. For repeatability, we found that even with the long timescales considered in this study, aggression and boldness were both repeatable – across the entire data set (∼0.4 and ∼0.3, respectively) using all lizards, as well as among years (∼0.4 and ∼0.4, respectively) using lizards observed in multiple years (93 for aggression, 73 for boldness). Repeatability did not differ substantially between the sexes. We found no syndrome between aggression and boldness – despite a weak positive correlation in multivariate mixed models, the 95% credible interval for this correlation included zero. Our results are notable because they demonstrate that wild animals may exhibit consistent personality differences in ecologically relevant behaviours over extended periods even in the face of substantial temporal variation in ecological and social factors, a fact that has likely ecological and evolutionary consequences.

Summary Few animals have experienced such jarring taxonomic whiplash as has Oculudentavis, a tiny tetrapod preserved in amber. A new specimen of this perplexing lineage now shows that it is a lizard unlike any ever discovered.

The two species of rock lizards, Darevsia raddei and Darevskia portschinskii, belong to two different phylogenetic clades of the same genus. They are supposed ancestors for the hybrid parthenogenetic, Darevskia rostombekowi. The present study aims to identify morphological features of these two species and the potential gene introgression between them in the area of sympatry. External morphological features provided the evidence of specific morphology in D. raddei and D. portschinskii: the species differed in scalation and ventral coloration pattern, however, they had some proportional similarities within both sexes of the two species. Males of both species had relatively larger heads and shorter bodies than females. Males of D. raddei were slightly larger than males of D. portschinskii and had longer hindlimbs. Microsatellite genotyping revealed no traces of hybridization or gene flow among these species. We suggest that the absence of individuals with combined morphological and genetic features of the studied species reflects existing reproductive barriers. The hybridization between two bisexual rock lizard species from distant clades is rare and only takes place under very specific environmental conditions.

The Central Ryukyus, a group of islands in southwestern Japan, harbor many endemic reptiles and amphibians, and the geographic ranges of the endemics are limited to south of the Tokara Gap, an old sea strait. Ateuchosaurus pellopleurus is a lizard with an exceptionally wide geographic range that encompasses the Central Ryukyus and north of the Tokara Gap. The intraspecific geographic variation of this species and the divergence time between A. pellopleurus and its sister species in southern China, Ateuchosaurus chinensis, were assessed by molecular phylogeographic analyses. The results indicated that the populations north of the gap were established by recent northward dispersal, prior to which the distribution of this species was limited to the Central Ryukyus. The estimated divergence time between A. pellopleurus and A. chinensis was in the Oligocene or Miocene, which was concordant with the divergence times of most Central Ryukyu endemics. These results demonstrated that A. pellopleurus is essentially a Central Ryukyu endemic that shares a common biogeographic history with other endemics. The common divergence times suggested that isolation of the endemics from their sister species in surrounding areas are attributable to geographic isolation by a tectonic event in the Miocene. In addition, A. pellopleurus showed distinct divergence between the populations in the northern and southern parts of the Central Ryukyus, and further diversification within and between islands in the southern part. Comparison of the phylogeographic patterns between this species and other endemics revealed that the present diversity in the Central Ryukyu endemics was formed by a complex history that involved occasional dispersal rather than simple vicariance events.

The human-assisted movement of species beyond their native range facilitates novel interactions between invaders and native species that can determine whether an introduced species becomes invasive and the nature of any consequences for native communities. Avoiding costly interactions through recognition and avoidance can be compromised by the naïvety of native species to novel invaders and vice versa. We tested this hypothesis using the common wall lizard, Podarcis muralis, and the native lizard species with which it may now interact in Britain (common lizard, Zootoca vivipara, sand lizard, Lacerta agilis) and on Vancouver Island (northern alligator lizard, Elgaria coerulea) by exploring species' responses (tongue flicks, avoidance behaviour) to heterospecific scent cues in controlled experiments. The tongue flick response of P. muralis depended on the different species’ scent, with significantly more tongue flicks directed to E. coerulea scent than the other species and the control. This recognition did not result in any other behavioural response in P. muralis (i.e. attraction, aggression, avoidance). Lacerta agilis showed a strong recognition response to P. muralis scent, with more tongue flicks occurring close to the treatment stimuli than the control and aggressive behaviour directed towards the scent source. Conversely, Z. vivipara spent less time near P. muralis scent cues than the control but its tongue flick rate was higher towards this scent in this reduced time, consistent with an avoidance response. There was no evidence of E. coerulea recognition of P. muralis scent in terms of tongue flicks or time spent near the stimuli, although the native species did show a preference for P. muralis-scented refuges. Our results suggest a variable response of native species to the scent of P. muralis, from an avoidance response by Z. vivipara that mirrors patterns of exclusion observed in the field to direct aggression observed in L. agilis and an ambiguous reaction from E. coerulea which may reflect a diminished response to a cue with a low associated cost. These results have significant implications for the invasive success and potential impacts of introduced P. muralis populations on native lizards.

Background: Alternatives to gross external anatomical sex determination are often required, peculiarly in species displaying poor or absent gross sexual dimorphism, such as the beaded lizard. This study evaluates results of hemipenile contrast radiography accuracy as compared to ultrasonography of the same beaded lizard (Heloderma alvarezi and Heloderma horridum). Methods: Eleven captive adult beaded lizards (4 H. alvarezi and 7 H. horridum), underwent hemipenis contrast radiography, and results compared with coelomic ultrasound. Results: By ultrasound, 2 lizards were females and 9 were males. By contrast hemipenis radiography, 2 animals were females and 9 were males. In this sample, there was a Kappa concordance of 1. Conclusions and clinical relevance: In this species, contrast hemipenis radiography proved to be a reliable diagnostic tool for hemipenes identification, and sex determination with all test specimens. Further studies including a larger number of animals and different lizard species are warranted.

REM sleep was initially described in mammals and was later found in birds. As the results obtained in reptiles were unconvincing, this suggested for years that only homeothermic species have REM sleep. However, recent studies in lizards also suggest the presence of two electrophysiological states and provide a better picture of their sleep. Nevertheless, due to differences in the expression of these states in two lizard species, as well as missing information, homology with mammalian REM sleep still could not be established. As ectotherms and homeotherms have very different physiology and neuroanatomy, we expect that, even if a state like REM sleep exists in ectotherms, its phenotypic expression should be different. Therefore, we think that a comprehensive understanding of the evolution of REM sleep will come from efforts to examine both the similarities and difference between sleep states in homeotherms and ectotherms.

Caudal autotomy, the voluntary shedding of a tail, is a last-ditch strategy used by many lizard species to escape from predators. There are several costs associated with caudal autotomy that may cause lizards to change their behaviour during tail regeneration. These behavioural changes may be dependent upon individual differences in response to autotomy (e.g. trait or state-dependent differences) and/or the degree of tail loss, as many lizards have the capacity to only partially shed their tail which probably entails fewer costs relative to complete autotomy. However, no study, to our knowledge, has considered how caudal autotomy, or the extent of autotomy, affects individual behavioural variation. Accordingly, we investigated the effects of both partial and complete tail loss on individual behavioural variation in delicate skinks, Lampropholis delicata. We found that lizards that experienced complete tail loss, on average, became less active and explorative and had much slower sprint speeds following autotomy. These lizards also became more predictable and consistent in their behaviour, exhibiting a notable decrease in their within-individual behavioural variance. In contrast, we did not see any significant behavioural effects in lizards that experienced partial tail loss. We also found a positive among-individual correlation between activity/exploration and neophilia, but tail loss had no effect on the structure of this syndrome. Our results suggest that complete tail loss may impose effects on traits more closely associated with locomotion and predator escape ability, while also constraining an individual's capacity for differential behavioural expression.

The difference between phenotypic and genotypic differentiation of conspecific populations is commonly used for detecting natural selection. However, phenotypic variation integrates both genetic and non-genetic components, and this may lead researchers to false conclusions. To avoid bias, the analysis of the heritability of individual phenotypic characters is important, but the means are labor–intensive and require controlled crosses. In this paper, we tried to get around these difficulties by working with a natural system comprised of the coexisting sexually reproducing lizard Darevskia portschinskii, and its daughter parthenogenetic form, Darevskia dahli. The excess of individual and between-population variation in the sexual form relative to the parthenogen was used as a measure of heritability of each of 21 scalation traits and principal components extracted from their analysis. We compared these data with microsatellite genotypes based on the analysis of five variable loci. We showed that D. portschinskii had higher individual and between-population phenotypic diversity than D. dahli. Phenotypic differences between populations of D. portschinskii (but not D. dahli) correlate with both the geographic distances and pairwise fixation indices based on the analysis of the genetic markers. This correlation substantially increased when, instead of the original phenotypic distances, the corrected Qst values are used to assess the heritability of the characters. A similar analysis pattern is recommended for various natural systems with coexisting sexually and asexually reproducing organisms.

The Twin-spotted Rattlesnake (Crotalus pricei) is a small lizard specialist restricted to higher montane habitat in the Sky Islands of Arizona and Mexico. Though this species is restricted to high elevations and dispersal between mountaintops is impossible, few studies have investigated venom composition or the predator-prey relationship between C. p. pricei and its primary prey source, Yarrow's Spiny Lizard (Sceloporus jarrovii). Because of current isolation of populations in disjunct mountain ranges, it is possible that populations show local adaptation to prey and/or environmental conditions, as reflected by distinct venom phenotypes. Here we characterize venom composition of C. pricei from several different Sky Island mountain ranges and its relationship with S. jarrovii by using various analytical techniques and comparative toxicity tests. Results of venom analyses indicate that there is limited geographic variation in venom composition, occurring primarily in venoms of C. pricei from Durango, Mexico, which had unusual PLA2 isoforms that are lacking from venoms of U.S. populations. Toxicity assays reveal that S. jarrovii has not developed resistance specific to C. p. pricei venom but does display a general tolerance to venom of several snakes in the genus Crotalus. These results provide insight into the evolutionary relationship between a lizard specialist and its natural prey, in addition to novel information on the venom composition of a little-studied species with a narrow range in the United States.

I here describe new fossil remains of lizards and snakes from the late Miocene of Pikermi, near Athens, Greece. This classical locality, known since at least the middle of the 19th century, has yielded over the decades abundant mammal fossils, whereas squamate remains have been confined to early discoveries of Varanus remains during the 19th century. The first specimen among these varanid fossils, a large vertebra described by Albert Gaudry during the 1860s, represents also one of the earliest discoveries of a fossil monitor lizard worldwide. Nevertheless, this historically important specimen has only been briefly described and its so far only available images were the original lithographs and subsequent sketches of two only of its views. I here describe this specimen in detail and provide photographs of all its standard views. The additional squamate remains from the Pikermi area are fragmentary. Nevertheless, they document the presence in Pikermi of other lizard groups, such as lacertids and probable anguines, while snakes are described for the first time. Among the snake fossils, probable erycines and colubrids are identified; if indeed an erycine, this would be the oldest occurrence of that group in the Eastern Mediterranean, thus extending back its stratigraphic range in the area by several million years.

Both environmental temperatures and spatial heterogeneity can profoundly affect the biology of ectotherms. In lizards, thermoregulation may show high plasticity and may respond to environmental shifts. In the context of global climate change, lizards showing plastic thermoregulatory responses may be favored. In this study, we designed an experiment to evaluate the extent to which lizard thermoregulation responds to introduction to a new environment in a snapshot of time. In 2014, we captured individuals of the Aegean Wall lizard (Podarcis erhardii) from Naxos Island (429.8 km(2)) and released them onto two small, lizard-free islets, Galiatsos (0.0073 km(2)) and Kampana (0.004 km(2)) (Aegean Sea, Greece). In 2017, we returned to the islets and estimated the effectiveness (E), accuracy and precision of thermoregulation measuring operative, preferred (T-pref) and body temperatures. We hypothesized that the three habitats would differ in thermal quality and investigated the extent to which lizards from Naxos demonstrate plasticity when introduced to the novel, islet habitats. Thermal parameters did not differ between Galiatsos and Naxos and this was reflected in the similar E and T-pref. However, lizards from Kampana deviated in all focal traits from Naxos, resulting in higher E and a preference for higher T-pref. In sum, Naxos lizards shifted their thermoregulatory profile due to the idiosyncratic features of their new islet habitat. Our results advocate a high plasticity in lizard thermoregulation and suggest that there is room for effective responses to environmental changes, at least for Podarcis lizards in insular habitats.

Ectotherms utilise a complex array of behavioural and physiological mechanisms to cope with variation in suboptimal thermal environments. However, these mechanisms may be insufficient for population persistence under contemporary climate change, resulting in a greater need to understand how local populations respond to geographic variation in climate. In this study, we explored the potential for local adaptation and acclimation in thermal traits and behaviours using wild and captive populations of a small agamid lizard (the jacky lizard, Amphibolurus muricatus). We predicted that wild lizards from a high elevation site would have cooler thermal preferences compared to those at low elevation sites to match the more restricted thermal resources at higher, cooler elevations. We additionally explored whether variation in thermal traits was due to recent acclimation or fixed population differences, such as due to developmental plasticity or local adaptation. In contrast to our predictions, we found high-elevation lizards began panting at higher temperatures and had higher thermal preferences relative to lower elevation lizards. When allowed to bask freely, there was no difference in the intensity of basking or daily duration of time spent basking between lizards from different elevations. Although the high-elevation lizards appeared to show stronger acclimation to recent air temperatures compared to low-elevation lizards, this difference was not significant. Similarly, captive lizards acclimated under long and short basking regimes showed no major differences in thermal traits or basking behaviour. Our results are consistent with the presence of counter-gradient variation in thermal phenotypes of lizards, and suggest that these are driven by local adaptive responses or developmental effects rather than recent acclimation.

Environmental temperature, particularly in habitats with extreme temperature fluctuations, may shape selection pressures on life history traits. Especially in ectotherms, temperature affects performance, physiology, and in some species, skin color. Skin color can be a sexual ornament signaling the bearer's ability to resist infections, when only high-quality individuals are able to invest both in high immune defense and elaborate ornament expression. However, how the information content of these sexual traits may vary with environmental conditions has been less studied. Dickerson's collared lizard (Crotaphytus dickersonae) males are blue and have a black and white collar. This conspicuous coloration signals performance and immune response, and is related to body temperature. Here, by maintaining males at higher, lower, and mean environmental temperatures we evaluated whether temperature variation influences color and constitutive innate humoral immunity (agglutination and lysis titers, estimated through hemolysis-hemagglutination assays), and whether extreme temperatures impose trade-offs between color and humoral immunity. We found that at low and high temperature treatments males had lower agglutination and lysis titers, and at low temperature, blue chroma from the dorsum declined and males became greener. Interestingly, at low and control temperature treatments, agglutination titer and blue coloration were positively correlated, whereas high temperatures revealed a trade-off between increasing agglutination titers and displaying bluer skin color. Our results suggest that in the Dickerson collared lizard even short-term variation of environmental temperature affects performance of constitutive innate humoral immunity and the brilliant blue skin color. Particularly, high temperatures may compromise some components of male's immunity and sexual signaling.

Segmentation gives rise to the anterior-posterior axis in many animals, and in vertebrates this axis comprises serially arranged vertebrae. Modifications to the vertebral column abound, and a recurring, but functionally understudied, change is the elongation of the body through the addition and/or elongation of vertebrae. Here, we compared the vertebral and axial kinematics of the robustly limbed Fire skink (Riopa fernandi) representing the ancestral form, the limbless European glass lizard (Ophisaurus apodus), and the Northern water snake (Nerodia sipedon). We induced these animals to traverse through channels and peg arrays of varied widths and densities, respectively, using high-speed X-ray and light video. We found that even though the snake had substantially more and shorter vertebrae than either lizard, intervertebral joint angles did not differ between species in most treatment levels. All three species decreased the amplitude and wavelength of their undulations as channels narrowed and the lizard species increased wave frequency in narrower channels. In peg arrays, both lizard species decreased wave amplitude, while the snake showed no differences. All three species maintained similar wavelengths and frequencies as peg density increased in most cases. Our results suggest that amplitude is decoupled from wavelength and frequency in all three focal taxa. The combination of musculoskeletal differences and the decoupling of axial kinematic traits likely facilitates the formation of different undulatory waves, thereby allowing limbless species to adopt different modes of locomotion.

Environmental temperatures play a vital role in the physiological and behavioral activity of ectotherms. Behavioral thermoregulation allows animals to modify their body temperature to optimize functions critical to fitness, including digestion, growth, reproduction, and locomotor performance. Diurnal reptiles are a classic model system to answer questions related to thermal ecology, whereas behavioral thermoregulation in nocturnal species is thought to be strongly constrained by low environmental thermal heterogeneity at night. The few studies describing the thermal ecology of nocturnal reptiles indicate a majority of thermoregulatory behavior (if any) occurs during the day within diurnal retreats, but few examined this behavior throughout the night. In tropical systems, thermal heterogeneity may remain high, even at night, allowing nocturnal ectotherms to thermoregulate through conduction on surfaces that retain heat after sunset. We investigated the thermoregulatory behavior of a tropical nocturnal gecko (Australian house gecko, Gehyra dubia) by measuring its preferred temperature in a thermal gradient, and selected body temperatures using radio telemetry, in relation to available operative environmental temperatures obtained using thermal models. Preferred body temperatures of geckos ranged from 31.4 ± 0.59–34.5 ± 0.55 °C in a laboratory thermal gradient. In the field, during winter, geckos were more effective thermoregulators than in the summer. In low thermal quality habitats, geckos sought rare, warm microclimates at night to maintain body temperatures warmer than most available environmental temperatures, and were highly effective thermoregulators. For ectotherms, appropriate environmental temperatures are a vital resource for survival, similar to food or shelter. The ability to exploit rare microclimates is especially important for nocturnal species, as heterogeneity of environmental temperatures is reduced at night compared to the day. In a warming world, it is vital to understand the thermal ecology of nocturnal ectotherms, as other species may shift to become more nocturnal to avoid lethal diurnal temperatures.

After tail loss in the African gecko Lygodactylus capensis (Smith, 1949) a new tail is regenerated, including caudal adhesive pads. The axial skeleton of the regenerating tail consists in an elastic cartilaginous tube replacing the original vertebrae that allows interacting with the substrate like in the original tail. The formation of adhesive setae has been analyzed using transmission and scanning electron microscopy coupled to immunolabeling for Corneous Beta Proteins. During progressive stages of epidermal differentiation new setae are developed at stage 4 of the shedding cycle and contain Corneous Beta Proteins. These structural proteins are faintly localized in the Oberhäutchen but are abundant in the beta-layer, indicating that the two epidermal layers have a different protein composition. The setae originate from the growth of Oberhäutchen spinulae into the cytoplasm of clear cells and the latter produce a thick fibrous meshwork of keratin and other unknown proteins localized around the growing setae. This cytoskeleton likely allows molding tail setae like for digital setae. A graded development of setae is observed from the base to the tip of regenerated pads and from the periphery to more central areas. The terminal end of the setae is subdivided into numerous filamentous spatulae that increase the adhesion contact. Sensory boutons are frequently detected at the margin of tail scales and adhesive pads, likely improving compliance with the substrate. The present study indicates that tail regeneration is a convenient experimental model to analyze adhesive setae formation, microstructures that allow to these lizards climbing vertical and arboreal substrates.

Inter-population variations in growth rate can result from independent or interactive effects of genetic and environmental factors, and be induced by some physiological differences as well. Toad-headed lizards (Phrynocephalus vlangalii) from a higher-elevation population were shown to have a higher growth rate than those from a lower-elevation population. The physiological basis of growth rate variation in this species is not well understood. Here, we investigated the feeding performance and resting metabolic rate (RMR) of lower- and higher-elevation individuals at different test ambient temperatures to evaluate the role of differences in energy intake, assimilation efficiency and metabolic expenditure on growth rate variations. Within the range of 25−35 °C, lizard RMR increased with increasing test ambient temperature, but food intake, apparent digestive coefficient (ADC, food energy minus faecal energy divided by food energy), and assimilation efficiency (AE, food energy minus faecal and urinary energy divided by food energy) were less thermally sensitive in both populations. Higher-elevation lizards tended to eat more food and have a lower RMR than lower-elevation ones, despite the lack of differences in ADC and AE. Our result showed that more energy intake and reduced maintenance cost may be associated with the higher growth rate of higher-elevation lizards. Accordingly, inter-population differences in energy acquisition and expenditure could act as potential sources for geographic variation in growth rate.

Multimodal signals are used by many animals for intraspecific communication and can provide information about sex identity as well as quality of the signaller. In diurnal geckos of the genus Cnemaspis, chromatic colour patches in males evolved after chemical secretions, providing us with an opportunity to examine the utility of evolving multimodality. We quantified signal components and receiver responses in Cnemaspis mysoriensis to determine the relative importance of chemical and visual traits for intraspecific communication. Digital imagery and spectrophotometry of lizards revealed the presence of two distinct male morphs (yellow-gular and white-gular) and one female form (white-gular). All males, but no females, had yellow eye rims. Characterization of chemical secretions from the ventral precloacal and femoral glands of all lizard forms revealed no differences between male morphs. However, all males differed from females in a few key compounds. We then exposed lizards to only chemical stimuli, only visual stimuli, or both chemical and visual stimuli of conspecific males and females. We found that females were responsive to the chemical stimuli alone as well as the multimodal stimuli of males, whereas males were only responsive to the multimodal stimuli of other males. Neither chemical or visual components of females elicited a response from conspecifics. Thus, while the chemical secretions of males are sufficient for females to elicit a response, multimodal stimuli are necessary for males to respond. Based on variation in signalling traits and receiver responses, we conclude that: (1) chemical secretions signal both sex identity and male quality; (2) eye rim colour encodes information about sex identity; and (3) gular colour in males is probably not a redundant trait, providing some information to males, but not females. We conclude that the secondary evolution of visual signals in C. mysoriensis therefore enhances male–male social interactions and not communication in general.

Although the importance of thermoregulation and plasticity as compensatory mechanisms for climate change has long been recognized, they have largely been studied independently. Thus, we know comparatively little about how they interact to shape physiological variation in natural populations. Here, we test the hypothesis that behavioral thermoregulation and thermal acclimatization interact to shape physiological phenotypes in a natural population of the diurnal lizard, Sceloporus torquatus. Every month for one year we examined thermoregulatory effectiveness and changes in the population mean in three physiological parameters: cold tolerance (Ctmin), heat tolerance (Ctmax), and the preferred body temperature (Tpref), to indirectly assess thermal acclimatization in population means. We discovered that S. torquatus is an active thermoregulator throughout the year, with body temperature varying little despite strong seasonal temperature shifts. Although we did not observe a strong signal of acclimatization in Ctmax, we did find that Ctmin shifts in parallel with nighttime temperatures throughout the year. This likely occurs, at least in part, because thermoregulation is substantially less effective at buffering organisms from selection on lower physiological limits than upper physiological limits. Active thermoregulation is effective at limiting exposure to extreme temperatures during the day, but is less effective at night, potentially contributing to greater plasticity in Ctmin than Ctmax. Importantly, however, Tpref tracked seasonal changes in temperature, which is one the factors contributing to highly effective thermoregulation throughout the year. Thus, behavior and physiological plasticity do not always operate independently, which could impact how organisms can respond to rising temperatures.

Animals raised in captivity during several generations may not express appropriate antipredator behaviour when reintroduced into the wild. Here we present the results of experiments to enhance behavioural responses to predators in adult males of the endangered lizard Gallotia simonyi (El Hierro, Canary Islands). Individuals were subjected to a training procedure (control, pre-training, training and post-training phases) using stuffed specimens of a kestrel and a cat as predators. We filmed all trials and compared relative durations of the more common behaviour patterns shown by lizards, both among experimental phases and before and after presentation of the stuffed predator. Locomotion and Basking were significantly reduced in the training and post-training trials and also after stimulus presentation, suggesting that the training protocol induced lizard avoidance over both predator models. To our knowledge, this is the first time lizards have been trained to show antipredator avoidance and our results provide the basis for a new management strategy that could be useful for reintroduction of captive-bred individuals of endangered species.

Reptiles are sensitive to temperature changes as ectotherm animals. The climate warming may pose more serious threat to reptiles. Although the behavior effect and reproduction biology have been well studied, little information is available about the adaptation mechanisms of reptiles to temperature stress. In this study, the native Chinese species, Eremias argus were incubated at 15 (cold stress), 25 (control group) and 35 °C (thermal stress) for 24 h. The transcriptome and metabolome technology were applied to investigate the molecular regulation mechanisms of lizards to acute temperature changes. The CIRBP and HSPA8 were hub genes in response to temperature adaptation. The increased expression of PER gene in lizard circadian rhythm is associated with tyrosine metabolism after cold or thermal stress. The poly-unsaturated fatty acids in female lizard liver were significantly increased with up-regulation of FASN and ACACA genes after thermal stress, which proved the disruption of fatty acid biosynthesis pathway in corporation with the altered body weight. The cortisol and testosterone were important steroid hormones in response to temperature changes especially in male lizard liver. The increased CIRBP gene expression in lizard gonads suppressed the KDM6B gene, which regulates the testis development and may induce sex reversal in male lizard after thermal stress. The adaptation responses of lizards to temperature stress may threaten the health status of wild population.

Oculudentavis khaungraae was described based on a tiny skull trapped in amber. The slender tapering rostrum with retracted osseous nares, large eyes, and short vaulted braincase led to its identification as the smallest avian dinosaur on record, comparable to the smallest living hummingbirds. Despite its bird-like appearance, Oculudentavis showed several features inconsistent with its original phylogenetic placement. Here we describe a more complete, specimen that demonstrates Oculudentavis is actually a bizarre lizard of uncertain position. The new interpretation and phylogenetic placement highlights a rare case of convergent evolution rarely seen among reptiles. Our results re-affirm the importance of Myanmar amber in yielding unusual taxa from a forest ecosystem rarely represented in the fossil record.

The kangaroo soft tick (Ornithodoros gurneyi) inhabits xeric habitats of Australia and, as a result, little is known about the natural hosts of the different life stages of this tick. Large macropods are inferred as the kangaroo soft tick's principal hosts since all life stages inhabit the loose soil of kangaroo wallows. These ticks have been reported to parasitize bearded dragons (Pogona barbata) and sleepy lizards (Tiliqua rugosa), however it is not known whether these lizards are competent hosts of this tick. In this study the prevalence and intensity of O. gurneyi parasitism on T. rugosa was examined by sampling lizards at a long-term study site spanning a precipitation-induced ecological gradient. The competence of T. rugosa as a host for O. gurneyi was explored by keeping larvae and nymphs of O. gurneyi, that had fed on T. rugosa, in captivity to determine if they will survive and moult. We found that O. gurneyi occurs throughout the study site, but that they were seldom recorded to parasitise T. rugosa. Still, it was noted that T. rugosa is a competent host of O. gurneyi. The results of this study indicate that kangaroos are not the only competent hosts of O. gurneyi and raises the question of whether T. rugosa and other lizards may play a role in the dispersal of these ticks.

The world's coral reef ecosystems are steadily being reconfigured by climate change. Lizard Island, on Australia's Great Barrier Reef, offers an opportunity to examine coral reef reassembly following disturbance, as this location has been impacted by consecutive tropical cyclones and consecutive coral bleaching events. Based on repeatedly monitoring the same 349 photoquadrats around Lizard Island over a 5-year period (2016–2021) we revealed that bleaching in 2016 drove a ∼50% reduction in hard coral cover, and a concomitant increase in algal turf cover. From 2018 to 2021, significant increases (>600%) in coral cover were detected on two semi-exposed reefs and were associated with substantial Acropora recruitment. By contrast, fourteen lagoonal and back reefs exhibited virtually no recovery nor Acropora recruitment. Given that the timeframe between disturbances is set to decrease, our results suggest that some recovery is possible immediately after severe cumulative disturbances, although this recovery may be highly spatially heterogenous.

Ticks are haematophagous arthropods that parasitise a wide range of vertebrate hosts. In Australia, there are currently 74 tick species described; 22 tick species have been reported parasitising humans. The stump-tailed lizard tick, Amblyomma albolimbatum, feeds on reptiles, most commonly lizards and snakes; however, we report the first case of A. albolimbatum parasitising a human. The nymphal tick was removed while conducting fieldwork on western tiger snakes (Notechis scutatus occidentalis) in an urban city environment near Perth, Western Australia. The tick was identified using morphological descriptions, which was further supported by the abundance of all parasitic stages of A. albolimbatum on the tiger snakes sampled. The number of tick species recorded from humans in Australia is now revised to 23 species. With the increasing incidence of tick-borne illnesses in Australia, this study highlights the need to report cases of new or atypical hosts, particularly humans, and especially when the ticks have been associated with zoonotic pathogens.

Reptiles are popular exotic pets and green iguanas (Iguana iguana) are amongst the top ten most popular reptiles. Here we describe a captive 8-year-old female green iguana that was referred for treatment of a non-healing, discharging lesion on the side of the body. The lesion was surgically excised and histopathological analysis revealed an epidermal proliferation of neoplastic keratinocytes, with focal infiltration through the basement membrane, into the underlying superficial dermis. Marked dysplastic changes, characterized by multifocal dyskeratosis and keratin pearl formation were also noted. A diagnosis of cutaneous squamous cell carcinoma (SCC) was made. Two years later, the iguana has shown no signs of recurrence. This is the first report of successful treatment of cutaneous SCC in a green iguana and contributes to the limited knowledge of cutaneous neoplasms in green iguanas.

The Pleistocenic Arc Hypothesis (PAH) posits that South American Seasonally Dry Tropical Forests (SDTF) were interconnected during Pleistocene glacial periods, enabling the expansion of species ranges that were subsequently fragmented in interglacial periods, promoting speciation. The lizard genus Lygodactylus occurs in Africa, Madagascar, and South America. Compared to the high diversity of African Lygodactylus, only two species are known to occur in South America, L. klugei and L. wetzeli, distributed in SDTFs and the Chaco, respectively. We use a phylogenetic approach based on mitochondrial (ND2) and nuclear (RAG-1) markers covering the known range of South American Lygodactylus to investigate (i) if they are monophyletic relative to their African congeners, (ii) if their divergence is congruent with the fragmentation of the PAH, and (iii) if cryptic diversity exists within currently recognized species. Maximum likelihood and Bayesian phylogenetic analyses recovered a well-supported monophyletic South American Lygodactylus, presumably resulting from a single trans-Atlantic dispersal event 29 Mya. Species delimitation analyses supported the existence of five putative species, three of them undescribed. Divergence times among L. klugei and the three putative undescribed species, all endemic to the SDTFs, are not congruent with the fragmentation of the PAH. However, fragmentation of the once broader and continuous SDTFs likely influenced the divergence of L. wetzeli in the Chaco and Lygodactylus sp. 3 (in a SDTF enclave in the Cerrado).

This project was funded by an ARC Discovery grant (DP130102998) to Martin Whiting and Richard Byrne and by Macquarie University. Behavioural flexibility, the ability to adjust behaviour to environmental change by adapting existing skills to novel situations, is key to coping with, for example, complex social interactions, seasonal changes in food availability or detecting predators. We tested the tree skink, Egernia striolata, a family-living skink from eastern Australia, in a set-shifting paradigm of eight colour/shape discriminations including reversals, an intradimensional acquisition of a new colour/shape and extradimensional shift from colour to shape (and vice versa). Skinks could learn to discriminate between colour/shape pairs and reverse this initial stimulus–reward association; however, they showed no significant decrease in the probability of making a correct choice in the extradimensional shift suggesting that they did not form an attentional set. Subjects appear to have learnt each stage as a new problem instead of generalizing stimuli into specific dimensions (set formation). In conclusion, tree skinks solved a discrimination reversal by focusing their attention towards visual stimuli and flexibly adjusting their choice behaviour accordingly. These lizards learned to use multidimensional visual stimuli to find a food reward but did not generalize stimuli into dimensions. Furthermore, this study is the first to test for set shifting in a lizard species and thereby allows us to extend set-shifting theory to a new taxon for comparison with primates, rodents, a bird and a turtle. Postprint

Ontogenetic shifts from an insectivorous diet towards an herbivorous one are well known in lizards. Energetic, behavioral and morphological factors have been linked to this pattern, but the latter have received less attention, especially with respect to head morphology. It is known that robust heads are related to stronger bite forces, consequently facilitating the consumption of harder or tougher, more fibrous items such as plants. In this study the ontogeny of diet and head morphology of the omnivorous tropidurid lizard Microlophus thoracicus are described. We found a significant ontogenetic shift from a mainly insectivorous diet in juveniles to a mainly herbivorous one in adults. In parallel, we measured the length, height and width of the head of the studied individuals. We found that adult individuals showed proportionally taller and wider heads when compared to juveniles, and that these increases in proportional head dimensions were significantly correlated with the increase in plant material in the diet that we observed. Additionally, we compared the morphologies of adults and juveniles of M. thoracicus and two other Microlophus species known to be insectivorous. These comparisons showed that M. thoracicus adults have proportionally more robust heads when compared to their insectivorous congeners, which is in agreement with the hypothesized link between head morphology and diet characteristics. The results of this study suggest that the known relationship between herbivory and head morphology is maintained even in an ontogenetic context, but further study is needed to determine the effect of other selective pressures which influence these changes in morphology.

The understanding of life-history responses to increased temperature is helpful for evaluating the potential of species for tackling future climate change. Herein, adult southern grass lizards, Takydromus sexlineatus, were maintained under two thermal regimes simulating current thermal environment and a 4 °C warming scenario to determine the effects of experimental warming on female reproduction and offspring phenotypes. Experimental warming caused females to oviposit earlier and more frequently; however, it did not affect other reproductive traits, including clutch size, egg mass and clutch mass. Accelerated embryonic development and energy accumulation rate might have occurred in warmed females. Maternal warming appeared to increase early embryonic mortality, but did not shift hatchling size and locomotor performance. Embryos of oviparous lizards might be more vulnerable to climate change at early stages than at later stages. The impacts of climate change in oviparous lizards might be adverse in the longer term because of the shift in pre-ovipositional embryo viability, which possibly led to a decreased number of hatchlings.

The lizard genus Bainguis was originally described from the Upper Cretaceous of Mongolia and attributed to Anguimorpha. The same genus was later reported from the Upper Cretaceous of Bayan Mandahu, Nei Mongol, China on the basis of a partial skeleton showing some similarities in osteoderm morphology. Re-examination of this specimen with the aid of μCT scanning suggests that it is, in fact, attributable to Parmeosaurus, a scincoid lizard described from the Ukhaa Tolgod locality, Mongolia, as do two new specimens from Bayan Mandahu. Moreover, some of the Mongolian material originally attributed to Bainguis appears also to belong to Parmeosaurus. And our new phylogenetic analysis confirms that Parmeosaurus is positioned on the stem of Scincoidea. Taken together, these specimens add new data to our understanding of Parmeosaurus but also raise questions as to the affinities of Bainguis.

Small lizards can accommodate to constraints imposed by temporal changes in ambient temperature through a combination of adaptive evolution and behavioral and physiological plasticity. Thermal physiology plasticity may compensate for climate variation and favor performance while minimizing behavioral costs in sub-optimal conditions. The Tandilia´s lizard, Liolaemus tandiliensis, occurs in an isolated mountain range of the Argentinean temperate Pampas. In this study, we compared the thermal biology of L. tandiliensis between late spring (December) and mid-summer (February). The habitats? thermal quality was lower in late spring than in midsummer. The lizard´s field-body temperature (Tb) was 2?3 °C higher than the operative temperature (Te). Overall, the mean preferred temperature (Tsel) was 37.4 °C [preferred range (Tset): 36.2?38.7 °C], and wassimilar to other Liolaemus species. The Tset and Tsel of females in late spring were 1.8 °C lower than in midsummer. In the case of males, the Tsel did not vary among seasons, while the Tset had a difference of 2.5 °C between seasons. Adults were moderate thermoregulators, but females were more efficient only in late spring (Emales = 0.69; Efemales = 0.58), compared to mid-summer (Emales = 0.68; Efemales = 0.50). Juveniles did not show temporal differences in temperature preferences and had a relatively higher efficiency in late spring (E = 0.38) compared to mid-summer (E=0.28). An increased proportion of juveniles and adults shifted their Tb near to the Tset in late spring respect to mid-summer. The adults also matched their preferred temperatures to their current body temperature. These results suggest that seasonal shifts in the thermoregulatory parameters of L. tandiliensis may improve their thermoregulatory efficiency. Although temporal variation in ambient temperatures might influence the thermal biology of the studied lizards, other factors such as changes in the reproductive status may have also interfered. Fil: Stellatelli, Oscar Aníbal. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina Fil: Villalba, Agustina. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Departamento de Biología; Argentina Fil: Block, Carolina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina Fil: Vega, Laura Estela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina Fil: Dajil, Juan Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina Fil: Cruz, Felix Benjamin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina

Ecology has long sought whether there are general assembly rules that underlie patterns of community organization. However, new perspectives of community disassembly and reassembly have emerged as environments depart from baseline conditions due to agents of global change. A trait-based approach can provide insights as to how changes affect performance of a species and their subsequent loss, gain, or persistence in an assemblage. We quantified the spatiotemporal dynamics in species and functional diversity from systematic surveys of local lizard assemblages distributed along an elevation gradient from three surveys in a 50-year period (1950s–2000s) in Big Bend National Park (BBNP), USA. BBNP was subjected to and then released from intensive grazing, which has resulted in changes to vegetative composition and cover. We examine changes in local assemblages in the context lizard functional traits, including thermal niche breadth. We hypothesized that temperature specialists were more likely to colonize or be lost from local sites. Species richness was lowest in the 1950s (N = 3 species), and subsequent surveys revealed that species richness increased in both the 1960s and 2000s (N = 6 and N = 8 species, respectively), but not all sites responded uniformly. We found that functional diversity in this system was not affected by this drastic increase species richness, indicative of functional redundancy in species traits. Lizards that were added to sites tended to be smaller bodied with lower thermal tolerances. Lizards with high preferred body temperatures were locally extirpated from high elevation sites that experienced high shrub encroachment, likely due to a reduction in the preferred thermal gradients these species. These results reveal that long-term desert lizard functional diversity was maintained, but the consequences of changes to functional diversity at the local scale need to be examined further.

We describe a conceptual framework integrating animal personalities, movement ecology, social networks and parasite transmission. For directly transmitted parasites, parasite transmission depends on social interaction patterns that can be quantified using social network metrics. For indirectly transmitted parasites, the key can be transmission networks that quantify time-lagged contacts (e.g. where potential hosts visit locations used earlier by infected hosts). Social network connections (time-lagged or not) often result from shared space use determined by individual movements in response to key environmental factors. Movement ecology provides a framework for understanding these responses. Finally, individuals with different personalities likely respond differently to environmental factors in ways that influence the movements and space use that underlie network connectivity, which, in turn, affects parasite loads and transmission. We illustrate these key points with recent work on sleepy lizards, Tiliqua rugosa, and their ticks. By GPS tracking of nearly all adult lizards at our site, we found that lizards that more frequently shared the same refuges (where ticks detach and reattach to a new host) used earlier by other lizards tended to indeed have higher tick loads. Higher shared refuge use was associated with greater shared space use, in general. Shared space use with conspecifics was reduced by the lizards' general propensity (quantified by analyses of 279 985 GPS locations for 72 lizards) to avoid conspecifics, but enhanced by their general tendency to prefer areas with more resources and better refuge (in particular, late in the season when food was scarce and conditions were hotter and drier). Both of these tendencies were personality dependent. Less aggressive lizards exhibited both a stronger attraction to areas with more food and better refuge, and a stronger tendency to avoid other lizards. We conclude by discussing implications of our results for the general conceptual framework and suggest future directions.

Environmental and developmental conditions can drive substantial variation in offspring behaviour and developmental trajectory. While incubation temperature is well known to influence development in oviparous animals, little is known of the role of parental temperature on offspring phenotype (i.e. thermal parental effects). Following exposure of male and gravid female jacky dragons, Amphibolurus muricatus, to one of two thermal treatments (short-bask versus long-bask) and incubation of their eggs at a constant temperature, we examined whether the preovipositional parental treatment influenced offspring performance-related behaviours. We detected main and interactive effects of parental treatment on offspring behaviours including feeding, exploration and antipredator. Sex-specific effects of parental treatment included long-bask sons being more likely to feed and being bolder following predatory attack than short-bask sons, while the differences between treatments for daughters were smaller. Behaviours were not consistent between 1 week and 1 month of age and showed little correlation across behavioural contexts. Some behaviours emerged as promising mechanisms of documented parental effects on offspring growth and survival in these individuals. In particular, boldness among long-bask sons in an antipredator context may be linked to their greater rates of growth posthatching. Overall, our findings suggest that thermal parental effects influence variation in animal behaviours relevant for subsequent fitness outcomes.

Peripheral nerves exhibit robust regenerative capabilities in response to selective injury among amniotes, but the regeneration of entire muscle groups following volumetric muscle loss is limited in birds and mammals. In contrast, lizards possess the remarkable ability to regenerate extensive de novo muscle after tail loss. However, the mechanisms underlying reformation of the entire neuromuscular system in the regenerating lizard tail are not completely understood. We have tested whether the regeneration of the peripheral nerve and neuromuscular junctions (NMJs) recapitulate processes observed during normal neuromuscular development in the green anole, Anolis carolinensis. Our data confirm robust axonal outgrowth during early stages of tail regeneration and subsequent NMJ formation within weeks of autotomy. Interestingly, NMJs are overproduced as evidenced by a persistent increase in NMJ density 120 and 250 days post autotomy (DPA). Substantial Myelin Basic Protein (MBP) expression could also be detected along regenerating nerves indicating that the ability of Schwann cells to myelinate newly formed axons remained intact. Overall, our data suggest that the mechanism of de novo nerve and NMJ reformation parallel, in part, those observed during neuromuscular development. However, the prolonged increase in NMJ number and aberrant muscle differentiation hint at processes specific to the adult response. An examination of the coordinated exchange between peripheral nerves, Schwann cells, and newly synthesized muscle of the regenerating neuromuscular system may assist in the identification of candidate molecules that promote neuromuscular recovery in organisms incapable of a robust regenerative response.

Food and feeding habits of the Arabian skink, Scincus hemprichii were investigated in Jazan province, southwest of Saudi Arabia. S. hemprichii individuals fed during eleven months of the year. The mass of food in the stomachs indicated that a high degree of foraging success occurred during the warm spring while the lowest was during winter with January as an exception to feeding by the lizard. Analysis of the contents of 60 stomachs revealed that the diet of S. hemprichii in the study area consisted of arthropods, with two species of beetles of the family Dermestidae (Dermestis vulpinus and Dermestis maculates) and three type of dipteran larvae, accounting for 76% of the total volume of the food items. Specimens collected during January had empty stomachs.

Desert squamates need to regulate their body temperature within a specific range in response to extreme temperatures. Variation of thermal resources through altitudinal and latitudinal gradients influences the thermal physiological traits and thermoregulation of organisms. In some species, the physiological requirements between populations can vary correlated with environmental conditions. In other species, the physiological parameters may remain similar across geographic gradients. In this study, we compared the thermal requirements and thermoregulatory strategies of a lizard (Callisaurus draconoides) that inhabits contrasting desert ecoregions across a latitudinal gradient. To assess thermoregulation of C. draconoides, we measured their field body temperature during periods of activity, the preferred body temperature in a laboratory thermal gradient and the environmental operative temperature in three contrasting sites. We also analyzed and compared three thermoregulatory indices (accuracy and effectiveness of thermoregulation and habitat thermal quality) for each population. Our results suggest that C. draconoides maintains similar thermal requirements and tolerances across its distribution range. Furthermore, their thermoregulation was accurate and effective in low thermal quality environments. Therefore, the thermoregulation in C. draconoides is essential to buffer extreme environmental conditions and avoid the deadly consequences of overheating in each ecoregion along the Baja California peninsula.

Sprint speed is a major performance trait in animal fitness involved in escaping from predators, obtaining food, and defending territory. Biotic and abiotic factors may influence sprint speed in lizards. Temperature decreases at higher altitude. Therefore, lizards at high elevations may require longer basking times to reach optimal body temperatures, increasing their vulnerability to predation and decreasing their time for other activities such as foraging or reproduction. Here, we tested whether the maximum sprint speed of a lizard that shows conservative thermal ecology varied along an altitudinal gradient comprising low (2500 m), middle (3400 m) and high-altitude (4300 m) populations. We also tested whether sprint speed was related to dorsal reflectance at different ecologically relevant temperatures. Given that the lizard Sceloporus grammicus shows conservative thermal ecology with altitude, we expected that overall average sprint speed would not vary with altitude. However, given that darker lizards heat up quicker, we expected that darker lizards would be faster than lighter lizards. Our results suggest that S. grammicus at high altitude are faster and darker at 30 °C, while lizards from low and middle altitude are faster and lighter in color at 20 °C than high altitude lizards. Also, our results suggest a positive relationship between sprint speed and dorsal skin reflectance at 10 and 20 °C. Sprint speed was also affected by snout-vent length, leg length, and leg thickness at 10 °C. These results suggest that, even though predation pressure is lower at extreme altitudes, other factors such as vegetation cover or foraging mode have influenced sprint speed.

Colorful ornaments are important visual signals for animal communication that can provide critical information about the quality of the signaler. In this study, we focused on different color characteristics of the abdominal patches of males of six lizard species from the genus Sceloporus. We addressed three main objectives. First, we examined if size, brightness, saturation, and conspicuousness of these ornaments are indicative of body size, condition, immune function, or levels of testosterone and corticosterone. Second, we evaluated if the distinct components of these abdominal patches (blue or green patches and black stripes) transmit similar information about the signaler, which would support the redundant signal hypothesis, or if these components are related to different phenotypic traits, which would support the multiple message hypothesis. Third, we compared the phenotypic correlates of these ornaments among our six species to understand the degree of conservatism in the signaling patterns or to find species-specific signals. Using data collected from males in natural conditions and a multi-model inference framework, we found that in most species the area of the patches and the brightness of the blue component are positively related to body size. Thus, these color characteristics are presumably indicative of the physical strength and competitive ability of males and these shared signals were likely inherited from a common ancestor. In half of the species, males in good body condition also exhibit relatively larger blue and black areas, suggesting that the expression of these ornaments is condition-dependent. Abdominal patches also provide information about immunocompetence of the males as indicated by different correlations between certain color characteristics and ectoparasite load, counts of heterophils, and the heterophil:lymphocyte ratio. Our findings reveal that area and brightness of the abdominal patches signal the size and body condition of males, whereas blue saturation and conspicuousness with respect to the surrounding substrate are indicative of immune condition, thus supporting the multiple message hypothesis. However, some of these correlations were not shared by all species and, hence, point to intriguing species-specific signals.

Reproduction is regulated by multiple factors that influence physiology and behavior to ensure the continuity of species. However, more work is needed to examine the complex relationships between environmental factors and endocrine transducers that modulate reproductive cycles, particularly in lizards. Here, we aimed to characterize the variation in plasma sex steroid levels in different stages of the reproductive cycle in the lizard Sceloporus torquatus and assess whether sex steroid levels were related to environmental factors (temperature, photoperiod, precipitation, and relative humidity) and body condition. Plasma concentrations of estradiol (E2) and progesterone (P4) from blood samples were quantified by enzyme-linked immunosorbent assay (ELISA) and radioimmunoanalysis (RIA), respectively. Our results indicate that sex steroid concentrations were positively related to follicular development but negatively related to temperature and precipitation. E2 increased as the follicles grew, and its concentrations were highest in the preovulatory phase. P4 showed a similar pattern and persisted during pregnancy. Changes in body condition were non-significant and mainly unrelated to the reproductive stage and plasma sex steroids. Our findings indicate that sex steroids change depending on the season and reproductive stage. We observed high concentrations of E2 and P4 in the late vitellogenic and preovulatory stages, probably because of their role in promoting vitellogenesis and ovulation. Additionally, we observed that follicular development is correlated with temperature and photoperiod. To better understand the mechanisms underlying reproduction, future studies of captive populations where environmental factors can be manipulated are needed.

By the 1890s, placental arrangements had been documented macroscopically in lizards and fishes, but placental studies on such species lagged far behind research on mammals. In 1891, the biologist Ercole Giacomini (at the University of Siena, Italy) published the first histological analysis of a reptile placenta. Focusing on a placentotrophic lizard (Chalcides chalcides) with a morphologically complex placenta, Giacomini documented the histological and cellular bases for placental nutrient transfer and gas exchange. In conjunction with a follow-up study in 1906, he demonstrated that placental structure is correlated with function and can vary dramatically between related species. Giacomini‘s work was highly influential in showing that placentation in lizards had converged evolutionarily on that of mammals, while establishing reptile placentology as a highly promising area for future research.

X-ray microcomputed tomography was used to reveal putative trematode metacercariae (Platyhelminthes: Digenea) located in cysts positioned at the base of the femora in a 100 myr agamid lizard preserved in Myanmar amber. The cysts are characterized and compared with encysted metacercariae recovered from a similar location in an extant Anolis lizard. This discovery provides evidence that lizards were serving as intermediate hosts of trematodes some 100 Ma.

Multimodal communication involves the use of signals and cues across two or more sensory modalities. The genus Liolaemus (Iguania: Liolaemidae) offers a great potential for studies on the ecology and evolution of multimodal communication, including visual and chemical signals. In this study, we analyzed the response of male and female Liolaemus pacha to chemical, visual and combined (multimodal) stimuli. Using cue-isolation tests, we registered the number of tongue flicks and headbob displays from exposure to signals in each modality. Number of tongue flicks was greater when a chemical stimulus was presented alone than in the presence of visual or multimodal stimuli. In contrast, headbob displays were fewer in number with visual and chemical stimuli alone, but significantly higher in number when combined. Female signallers triggered significantly more tongue flicks than male signallers, suggesting that chemical cues are involved in sexual recognition. We did not find an inhibition between chemical and visual cues. On the contrary, we observed a dominance of the chemical modality, because when presented with visual stimuli, lizards also responded with more tongue flicks than headbob displays. The total response produced by multimodal stimuli was similar to that of the chemical stimuli alone, possibly suggesting non-redundancy. We discuss whether the visual component of a multimodal signal could attract attention at a distance, increasing the effectiveness of transmission and reception of the information in chemical cues. Fil: Vicente, Natalin Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - Tucumán. Unidad Ejecutora Lillo; Argentina Fil: Halloy, Monique. Fundación Miguel Lillo; Argentina

Foraging strategies aim to maximize the amount of food obtained while minimizing searching costs. To reduce these costs, animals use different strategies based on the use of personal or social information to exploit food patches. At the same time, the social attraction for food resources could increase competition intensity for them. Prior experiences of animals regarding social risk and the foreknowledge of the competitors might drive the foraging strategies. In this paper, we examined experimentally whether rock lizards used behavioural strategies to reduce the risks of foraging in presence of potential competitors. We measured the foraging behaviour of a lizard resident to a territory (i.e. terrarium), in the presence of both familiar and unfamiliar conspecifics (potential competitors). We considered whether foraging choices between two food sources of different value (i.e. quantity) are influenced by familiarity with the intruder and the evaluation of its competitive ability based on body size differences between lizards. We found differences in the number of attacks performed to the best food source, with more attacks when the intruder was unfamiliar. The results suggest evidence of both dear enemy recognition and current rival assessment modulate the foraging choices depending on the identity and the social relationship with the intruder., Financial support was provided by the Spanish Ministerio de Economía y Competitividad [project MINECO CGL2014-53523-P] and by the Spanish Ministerio de Ciencia, Innovación y Universidades [project PGC2018-093592-B-I00 (MCIU/AEI/FEDER,UE)

Representative locomotion types in lizards include terrestrial, arboreal, grass swimmer, sand swimmer and bipedal. Few studies explain the locomotion habit of extinct lizards, and even less asses those of bipedal ones. Here, we use quantitative methods to infer the type of locomotion of two Albian Mexican lizards (Lower Cretaceous) and three Cretaceous lizards from Brazil, North America and Spain, assessing the similarities of the hindlimb-forelimb length ratio amongst extinct and extant species. Additionally, an ancestral character state reconstruction analysis was performed, to evaluate the evolution of lizard locomotion habits. The species Huehuecuetzpalli mixtecus was bipedal while Tijubina pontei was facultative bipedal, Hoyalacerta sanzi, Tepexisaurus tepexii and Polyglyphanodon sternbergi cannot be differentiated amongst terrestrial or arboreal with the approach used in this work. The ancestral character state reconstruction analysis showed a terrestrial ancestral locomotion type, with a basal character state of hindlimbs longer than forelimbs. Equal length between hind and forelimbs appear to be a derivate state that evolved multiple times in lizard evolutionary history.

Oculudentavis khaungraae was described based on a tiny skull trapped in amber. The slender tapering rostrum with retracted narial openings, large eyes, and short vaulted braincase led to its identification as the smallest avian dinosaur on record, comparable to the smallest living hummingbirds. Despite its bird-like appearance, Oculudentavis showed several features inconsistent with its original phylogenetic placement. Here, we describe a more complete specimen that demonstrates Oculudentavis is actually a bizarre lizard of uncertain position. The new specimen is described as a new species within the genus Oculudentavis. The new interpretation and phylogenetic placement highlight a rare case of convergent evolution in skull proportions but apparently not in morphological characters. Our results re-affirm the importance of Myanmar amber in yielding unusual taxa from a forest ecosystem rarely represented in the fossil record. Fil: Bolet, Arnau. Universitat Autonoma de Barcelona; España Fil: Stanley, Edward L.. Florida Museum Of Natural History; Estados Unidos Fil: Daza, Juan D.. Sam Houston State University; Estados Unidos Fil: Arias Becerra, Joan Salvador. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - Tucumán. Unidad Ejecutora Lillo; Argentina Fil: Cernansky, Andrej. Comenius University In Brastislava; Eslovaquia Fil: Vidal García, Marta. University of Calgary. Department of Cell Biology and Anatomy; Canadá Fil: Bauer, Aaron M.. Villanova University; Estados Unidos Fil: Bevitt, Joseph J.. Australian Nuclear Science And Technology Organisation; Australia Fil: Peretti, Adolf. Peretti Museum Foundation; Suiza Fil: Evans, Susan E.. University College London; Estados Unidos