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3,538 results for “Lizard”
Data from: Your infections are what you eat: how host ecology shapes the helminth parasite communities of lizards
1. Understanding how parasite communities are assembled, and the factors that influence their richness, can improve our knowledge of parasite-host interactions and help to predict the spread of infectious diseases. Previous comparative analyses have found significant influences of host ecology and life history, but focused on a few select host taxa. 2. Host diet and habitat use play key roles in the acquisition of parasitic helminths as many are trophically-transmitted, making these attributes potentially key indicators of infection risk. Given the paucity of comparative studies with non-piscine, non-avian or non-mammalian hosts, it is critical to examine the degree to which host ecology influences parasite communities in other host taxa in order to identify common drivers. 3. We examined helminth diversity in over 350 species of lizards in relation to their body mass, ecology (diet and habitat use), and life history (clutch size, and ovo- or viviparity) using previously published data. 4. Overall, lizard species with herbivorous diets harboured fewer types of helminths (especially larval stages), with similar results for traits that were ultimately strongly associated with diet (host mass and habitat use). Large hosts tended to be herbivores with few helminth types whereas species utilizing arboreal habitats typically consumed some animal matter and hosted more helminths. 5. Understanding how host ecology and life history are related to their parasite assemblages has significant implications for the risk of acquiring novel parasites. Our results indicate an overwhelming influence of host diet such that many helminths may be relatively easily acquired by hosts in new ranges, or through dietary shifts.
Data from: Take this broken tail and learn to jump: the ability to recover from reduced in-air stability in tailless green anole lizards (Anolis carolinensis [Squamata: Dactyloidae])
Locomotion is involved in various fitness related tasks, such as foraging, acquiring mates and escaping from predators. Despite the importance of locomotor performance in determining fitness, animals often encounter situations in nature during which their locomotor performance is severely compromised. For animals that actively discard appendages as an antipredator strategy, the loss of appendages can cause a severe reduction in locomotor performance. However, whether animals can compensate for the impact on locomotor performance after autotomy is still unclear. A previous study has shown that tailless green anole lizards suffered from reduced in-air stability during jumping. In this study, we monitored jump kinematics in three groups of Anolis carolinensis for five consecutive weeks to test two hypotheses. First, whether tailless green anoles can recover from reduced in-air stability before their tails can regenerate. Second, whether gaining locomotor experience facilitates locomotor recovery. Our results revealed extensive individual variation in the ability to compensate for reduced in-air stability. Some individuals did improve in-air stability during the study period, whereas others showed no sign of improvement. Moreover, the acquisition of locomotor experience did not facilitate the recovery process. Our findings suggested that tail autotomy in green anoles likely imposes a long-term fitness disadvantage. The utility of other compensatory mechanisms, such as altering behavior, might play a role in natural populations to minimize the impact of autotomy on individual fitness. Our findings also shed some light on the independent evolutionary losses of the ability to autotomize within lizards. Comparative studies which test whether species that autotomize more frequently/easily can better compensate for the effect of autotomy would be a fruitful direction of future research.
Data from: Genome reannotation of the lizard Anolis carolinensis based on 14 adult and embryonic deep transcriptomes
Background: The green anole lizard, Anolis carolinensis, is a key species for both laboratory and field-based studies of evolutionary genetics, development, neurobiology, physiology, behavior, and ecology. As the first non-avian reptilian genome sequenced, A. carolinesis is also a prime reptilian model for comparison with other vertebrate genomes. The public databases of Ensembl and NCBI have provided a first generation gene annotation of the anole genome that relies primarily on sequence conservation with related species. A second generation annotation based on tissue-specific transcriptomes would provide a valuable resource for molecular studies. Results: Here we provide an annotation of the A. carolinensis genome based on de novo assembly of deep transcriptomes of 14 adult and embryonic tissues. This revised annotation describes 59,373 transcripts, compared to 16,533 and 18,939 currently for Ensembl and NCBI, and 22,962 predicted protein-coding genes. A key improvement in this revised annotation is coverage of untranslated region (UTR) sequences, with 79% and 59% of transcripts containing 5' and 3' UTRs, respectively. Gaps in genome sequence from the current A. carolinensis build (Anocar2.0) are highlighted by our identification of 16,542 unmapped transcripts, representing 6,695 orthologues, with less than 70% genomic coverage. Conclusions: Incorporation of tissue-specific transcriptome sequence into the A. carolinensis genome annotation has markedly improved its utility for comparative and functional studies. Increased UTR coverage allows for more accurate predicted protein sequence and regulatory analysis. This revised annotation also provides an atlas of gene expression specific to adult and embryonic tissues.
Data from: Uterine gene expression in the live-bearing lizard, Chalcides ocellatus, reveals convergence of squamate reptile and mammalian pregnancy mechanisms
Although the morphological and physiological changes involved in pregnancy in live-bearing reptiles are well studied, the genetic mechanisms that underlie these changes are not known. We used the viviparous African Ocellated Skink, Chalcides ocellatus, as a model to identify a near complete gene expression profile associated with pregnancy using RNA-Seq analyses of uterine transcriptomes. Pregnancy in C. ocellatus is associated with upregulation of uterine genes involved with metabolism, cell proliferation and death, and cellular transport. Moreover, there are clear parallels between the genetic processes associated with pregnancy in mammals and Chalcides in expression of genes related to tissue remodeling, angiogenesis, immune system regulation, and nutrient provisioning to the embryo. In particular, the pregnant uterine transcriptome is dominated by expression of proteolytic enzymes that we speculate are involved both with remodeling the chorioallantoic placenta and histotrophy in the omphaloplacenta. Elements of the maternal innate immune system are downregulated in the pregnant uterus, indicating a potential mechanism to avoid rejection of the embryo. We found a downregulation of major histocompatability complex loci and estrogen and progesterone receptors in the pregnant uterus. This pattern is similar to mammals but cannot be explained by the mammalian model. The latter finding provides evidence that pregnancy is controlled by different endocrinological mechanisms in mammals and reptiles. Finally, 88% of the identified genes are expressed in both the pregnant and the nonpregnant uterus, and thus, morphological and physiological changes associated with C. ocellatus pregnancy are likely a result of regulation of genes continually expressed in the uterus rather than the initiation of expression of unique genes.
Data from: Speciation with gene flow in whiptail lizards from a Neotropical xeric biome
Two main hypotheses have been proposed to explain the diversification of the Caatinga biota. The riverine barrier hypothesis (RBH) claims that the São Francisco River (SFR) is a major biogeographic barrier to gene flow. The Pleistocene climatic fluctuation hypothesis (PCH) states that gene flow, geographic genetic structure, and demographic signatures on endemic Caatinga taxa were influenced by Quaternary climate fluctuation cycles. Herein we analyze genetic diversity and structure, phylogeographic history, and diversification of a widespread Caatinga lizard (Cnemidophorus ocellifer) based on large geographical sampling for multiple loci to test the predictions derived from the RBH and PCH. We inferred two well-delimited lineages (Northeast and Southwest) that have diverged along the Cerrado-Caatinga border during the Mid-Late Miocene (6–14 Ma) despite the presence of gene flow. We reject both major hypotheses proposed to explain diversification in the Caatinga. Surprisingly, our results revealed a striking complex diversification pattern where the Northeast lineage originated as a founder effect from a few individuals located along the edge of the Southwest lineage that eventually expanded throughout the Caatinga. The Southwest lineage is more diverse, older, and associated to the Cerrado-Caatinga boundaries. Finally, we suggest that C. ocellifer from the Caatinga is composed of two distinct species. Our data support speciation in the presence of gene flow and highlight the role of environmental gradients in the diversification process.
Data from: Hormonally mediated increases in sex-biased gene expression accompany the breakdown of between-sex genetic correlations in a sexually dimorphic lizard
The evolution of sexual dimorphism is predicted to occur through reductions in between-sex genetic correlations (rmf) for shared traits, but the physiological and genetic mechanisms that facilitate these reductions remain largely speculative. Here, we use a paternal half-sibling breeding design in captive brown anole lizards (Anolis sagrei) to show that the development of sexual size dimorphism is mirrored by the ontogenetic breakdown of rmf for body size and growth rate. Using transcriptome data from the liver (which integrates growth and metabolism), we show that sex-biased gene expression also increases dramatically between ontogenetic stages bracketing this breakdown of rmf. Ontogenetic increases in sex-biased expression are particularly evident for genes involved in growth, metabolism, and cell proliferation, suggesting that they contribute to both the development of sexual dimorphism and the breakdown of rmf. Mechanistically, we show that treatment of females with testosterone stimulates the expression of male-biased genes while inhibiting the expression of female-biased genes, thereby inducing male-like phenotypes at both organismal and transcriptomic levels. Collectively, our results suggest that sex-specific modifiers such as testosterone can orchestrate sex-biased gene expression to facilitate the phenotypic development of sexual dimorphism while simultaneously reducing genetic correlations that would otherwise constrain the independent evolution of the sexes.
Data from: Testing hypotheses for genealogical discordance in a rainforest lizard
Genealogical discordance, or when different genes tell distinct stories although they evolved under a shared history, often emerges from either coalescent stochasticity or introgression. In this study, we present a strong case of mito-nuclear genealogical discordance in the Australian rainforest lizard species complex of Saproscincus basiliscus and S. lewisi. One of the lineages that comprises this complex, the Southern S. basiliscus lineage, is deeply divergent at the mito- chondrial genome but shows markedly less divergence at the nuclear genome. By placing our results in a comparative context and reconstructing the lineages' demography via multi-locus and coalescent-based Approximate Bayesian Computation (ABC) methods, we test hypotheses for how coalescent variance and introgression contribute to this pattern. These analyses suggest that the observed genealogical discordance likely results from introgression. Further, to generate such strong discordance, introgression probably acted in concert with other factors promoting asymmetric gene flow between the mitochondrial and nuclear genomes, such as selection or sex-biased dispersal. This study offers a framework for testing sources of genealogical discordance and suggests that historical introgression can be an important force in shaping the genetic diversity of species and their populations.
Data from: The genetic basis of discrete and quantitative colour variation in the polymorphic lizard, Ctenophorus decresii
Background: Colour polymorphic species provide invaluable insight into processes that generate and maintain intra-specific variation. Despite an increasing understanding of the genetic basis of discrete morphs, sources of colour variation within morphs remain poorly understood. Here we use the polymorphic tawny dragon lizard Ctenophorus decresii to test simple Mendelian models for the inheritance of discrete morphs, and to investigate the genetic basis of continuous variation among individuals across morphs. Males of this species express either orange, yellow, orange surrounded by yellow, or grey throats. Although four discrete morphs are recognised, the extent of orange and yellow varies greatly. We artificially elevated testosterone in F0 females and F1 juveniles to induce them to express the male throat colour polymorphism, and quantified colour variation across the pedigree. Results: Inheritance of discrete morphs in C. decresii best fit a model whereby two autosomal loci with complete dominance respectively determine the presence of orange and yellow. However, a single locus model with three co-dominant alleles for orange, yellow and grey could not be definitively rejected. Additionally, quantitative expression of the proportion of orange and yellow on the throat was strongly heritable (orange: h2 = 0.84 ± 0.14; yellow: h2 = 0.67 ± 0.19), with some evidence for covariance between the two. Conclusions: Our study supports the theoretical prediction that polymorphism should be governed by few genes of major effect, but implies broader genetic influence on variation in constituent morph traits.
Data from: Cryptic diversity and discordance in single-locus species delimitation methods within horned lizards (Phrynosomatidae: Phrynosoma)
Biodiversity reduction and loss continues to progress at an alarming rate, and thus there is widespread interest in utilizing rapid and efficient methods for quantifying and delimiting taxonomic diversity. Single-locus species-delimitation methods have become popular, in part due to the adoption of the DNA barcoding paradigm. These techniques can be broadly classified into tree-based and distance-based methods depending on whether species are delimited based on a constructed genealogy. Although the relative performance of these methods has been tested repeatedly with simulations, additional studies are needed to assess congruence with empirical data. We compiled a large data set of mitochondrial ND4 sequences from horned lizards (Phrynosoma) to elucidate congruence using four tree-based (single-threshold GMYC, multiple-threshold GMYC, bPTP, mPTP) and one distance-based (ABGD) species delimitation models. We were particularly interested in cases with highly uneven sampling and/or large differences in intraspecific diversity. Results showed a high degree of discordance among methods, with multiple-threshold GMYC and bPTP suggesting an unrealistically high number of species (29 and 26 species within the P. douglasii complex alone). The single-threshold GMYC model was the most conservative, likely a result of difficulty in locating the inflection point in the genealogies. mPTP and ABGD appeared to be the most stable across sampling regimes and suggested the presence of additional cryptic species that warrant further investigation. These results suggest that the mPTP model may be preferable in empirical data sets with highly uneven sampling or large differences in effective population sizes of species.
Data from: Reduction of baseline corticosterone secretion correlates with climate warming and drying across wild lizard populations
1. Climate change should lead to massive loss of biodiversity in most taxa but the detailed physiological mechanisms underlying population extinction remain largely elusive so far. In vertebrates, baseline levels of hormones such as glucocorticoids (GCs) may be indicators of population state since their secretion to chronic stress can impair survival and reproduction. However, the relationship between GC secretion, climate change and population extinction risk remains unclear. 2. In this study we investigated whether levels of baseline corticosterone (the main GCs in reptiles) correlate with environmental conditions and associated extinction risk across wild populations of the common lizard Zootoca vivipara. 3. First, we performed a cross-sectional comparison of baseline corticosterone levels along an altitudinal gradient among 14 populations. Then, we used a longitudinal study in 8 populations to examine the changes in corticosterone levels following the exposure to a heat wave period. 4. Unexpectedly, baseline corticosterone decreased with increasing thermal conditions at rest in females, and was not correlated with extinction risk. In addition, baseline corticosterone levels decreased after exposure to an extreme heat wave period. This seasonal corticosterone decrease was more pronounced in populations without access to standing water. 5. We suggest that low basal secretion of corticosterone may entail down-regulating activity levels and limit exposure to adverse climatic conditions, especially to reduce water loss. These new insights suggest that rapid population decline might be preceded by a down-regulation of the corticosterone secretion.
Data from: Testing Phylogenetic Methods with Tree Congruence: Phylogenetic Analysis of Polymorphic Morphological Characters in Phrynosomatid Lizards
Congruence between trees from separately analyzed data sets is a powerful approach for assessing the performance of phylogenetic methods but has been applied primarily to the analysis of molecular data. In this study, different methods for treating polymorphic characters were compared using morphological data from phrynosomatid lizards. Clades were identified that are both traditionally recognized and supported by recent molecular analyses, and species were sampled from these clades to make three RknownS phylogenies of eight species each. The ability of different methods to estimate these "known" phylogenies with a finite sample of characters was tested. The phylogenetic methods included eight parsimony methods for coding polymorphism, three distance approaches (UPGMA, neighbor joining, and Fitch-Margoliash) applied to two genetic distance measures (Nei's and the modified Cavalli-Sforza and Edwards chord distance), and continuous maximum likelihood. The effects of excluding polymorphic characters and character weighting (a priori and successive) were also tested. Among the different parsimony approaches, the fixed-only method (excluding all polymorphic characters) performed relatively poorly, whereas the frequency method (including all polymorphic characters) performed relatively well. However, frequency-based distance methods consistently outperformed parsimony, especially with a small sample size (n= 1 individual per species). These results agree closely with those from recent simulation studies of polymorphic data and argue against the common practices of excluding polymorphic morphological characters, ignoring the frequencies of traits within species, and the exclusive use of parsimony to analyze morphological data.
Data from: Information content is more important than sensory system or physical distance in guiding the long-term evolutionary relationships between signaling modalities in Sceloporus lizards
Long-term signal evolution is shaped by a variety of selective pressures including the need to convey additional information or to improve message transfer to specific receivers or through multiple environments. Here, we test the relative importance of information and sensory modality in shaping the long-term evolution of multimodal signals in Sceloporus lizards. To broadcast identity at territorial boundaries, male Sceloporus use both visual motion (headbob) and chemical signals, whereas they use color (blue belly patches) to signal aggression. Using modern phylogenetic comparative methods, we found a negative correlation between evolutionary changes in visual motion (headbobs) and chemical (femoral pore) signals, but only indirect ties between the evolution of color and motion signals (both of which are perceived visually) through viviparity, and no evidence of an evolutionary link between color and chemical signals. We also find a negative correlation between arboreality and chemical signals. Thus, information content (in this case, broadcasting individual identity versus signaling aggression) appears to play a more important role than sensory modality or physical distance in guiding long-term signal evolution. Additional insights into the underlying evolutionary processes are described, illustrating the utility of a phylogenetic approach.
Data from: Ornament size and colour as alternative strategies for effective communication in gliding lizards
Sexual ornamentation needs to be conspicuous to be effective in attracting potential mates and defending territories and indeed, a multitude of ways exists to achieve this. Two principal mechanisms for increasing conspicuousness are to increase the ornament's colour or brightness contrast against the background and to increase the size of the ornament. We assessed the relationship between the colour and size of the dewlap, a large extendible throat-fan, across a range of species of gliding lizards (Agamidae; genus Draco) from Malaysia and the Philippines. We found a negative relationship across species between colour contrast against the background and dewlap size in males, but not in females, suggesting that males of different species use increasing colour contrast and dewlap size as alternative strategies for effective communication. Male dewlap size also increases with increasing sexual size dimorphism, and dewlap colour and brightness contrast increase with increasing sexual dichromatism in colour and brightness, respectively, suggesting that sexual selection may act on both dewlap size and colour. We further found evidence that relative predation intensity, as measured from predator attacks on models placed in the field, may play a role in the choice of strategy (high chromatic contrast or large dewlap area) a species employs. More broadly, these results highlight that each component in a signal (such as colour or size) may be influenced by different selection pressures and that by assessing components individually, we can gain a greater understanding of the evolution of signal diversity.
Data from: Stochastic faunal exchanges drive diversification in widespread Wallacean and Pacific island lizards (Squamata: Scincidae: Lamprolepis smaragdina)
Aim: Widespread species found in disturbed habitats are often expected to be human commensals. In island systems, this association predicts that dispersal will be mediated by humans. We investigated the biogeographical relationships among populations of a widespread tree skink that inhabits coastal forest and human-cultivated plantations in Southeast Asia. We sought to determine whether populations of the emerald tree skink, Lamprolepis smaragdina, dis- persed via mechanisms that were not human-mediated ('natural' dispersal) or whether dispersal was mediated by humans. The latter scenario predicts low levels of genetic differentiation across a species' range, coupled with a genetic signature of recent range expansion. Location: Southeast Asia, the Philippines, Wallacea and the south-western Pacific. Methods: We analysed sequences of mitochondrial DNA from 204 samples collected throughout the range of this species. We use phylogenetic and popu- lation genetic methods to distinguish between predicted geographical patterns of genetic variation that might indicate natural or human-mediated dispersal. Results: In contrast to predictions derived from similar studies of taxonomy and natural history, we found L. smaragdina to be characterized by highly structured and seemingly geographically stable mitochondrial gene lineages. Main conclusions: Our results demonstrate a novel pattern of widespread species distribution, never before observed in vertebrates of the Indo-Australian Archipelago. Although this widespread and highly dispersive species is capable of long-distance dispersal, and has a clear history of over-water dispersal, it exhibits sharp genetic differentiation across its range. Our results suggest that random waif dispersal has been a pervasive ongoing phenomenon throughout the evolutionary history of this species.
Data from: Unidirectional pulmonary airflow patterns in the savannah monitor lizard
The unidirectional airflow patterns in the lungs of birds have long been considered a unique and specialized trait associated with the oxygen demands of their volant lifestyle, endothermic metabolism and unusual pulmonary architecture; however, the discovery of similar flow patterns in the lungs of crocodilians indicates that this character is likely ancestral for all archosaurs, the group that includes extant birds and crocodilians as well as their extinct relatives, such as pterosaurs and dinosaurs. Unidirectional flow in birds results from aerodynamic valves, rather than from sphincters or other physical mechanisms, and similar aerodynamic valves appear to be at work in crocodilians. Due to anatomical and developmental similarities in the primary and secondary bronchi of birds and crocodilians, these structures and airflow patterns may be homologous. Thus the origin of this pattern is at least as old as the split between crocodilians and birds, which occurred in the Triassic; however, it is possible that this pattern of flow is even older. This constitutes an alternative hypothesis, which can be tested by investigating patterns of airflow in members of the outgroup to birds and crocodilians, the Lepidosauromorpha (tuatara, lizards, and snakes). Here we show region-specific unidirectional airflow in the lungs of the savannah monitor lizard (Varanus exanthematicus). The presence of unidirectional flow in the lungs of V. exanthematicus thus gives rise to two possible evolutionary scenarios: (1) unidirectional airflow evolved independently in archosaurs and monitor lizards, or (2) these flow patterns are homologous in archosaurs and V. exanthematicus, having evolved only once in ancestral diapsids. If unidirectional airflow is plesiomorphic for Diapsida, this respiratory character can be reconstructed for extinct diapsids, and evolved in a small ectothermic tetrapod during the Paleozoic Era at least 100 million years before the origin of birds.
Data from: Evolution of viviparity: a phylogenetic test of the cold-climate hypothesis in Phrynosomatid lizards
The evolution of viviparity is a key life-history transition in vertebrates, but the selective forces favoring its evolution are not fully understood. With >100 origins of viviparity, squamate reptiles (lizards and snakes) are ideal for addressing this issue. Some evidence from field and laboratory studies supports the "cold-climate" hypothesis, wherein viviparity provides an advantage in cold environments by allowing mothers to maintain higher temperatures for developing embryos. Surprisingly, the cold-climate hypothesis has not been tested using both climatic data and phylogenetic comparative methods. Here, we investigate the evolution of viviparity in the lizard family Phrynosomatidae using GIS-based environmental data, an extensive phylogeny (117 species), and recently developed comparative methods. We find significant relationships between viviparity and lower temperatures during the warmest (egg-laying) season, strongly supporting the cold-climate hypothesis. Remarkably, we also find that viviparity tends to evolve more frequently at tropical latitudes, despite its association with cooler climates. Our results help explain this and two related patterns that seemingly contradict the cold-climate hypothesis: the presence of viviparous species restricted to low-elevation tropical regions and the paucity of viviparous species at high latitudes. Finally, we examine whether viviparous taxa may be at higher risk of extinction from anthropogenic climate change.
Data from: Semicircular canals in Anolis lizards: ecomorphological convergence and ecomorph affinities of fossil species
Anolis lizards are a model system for the study of adaptive radiation and convergent evolution. Greater Antillean anoles have repeatedly evolved six similar forms or ecomorphs: crown-giant, grass-bush, twig, trunk, trunk-crown and trunk-ground. Members of each ecomorph category possess a specific set of morphological, ecological and behavioural characteristics which have been acquired convergently. Here we test whether the semicircular canal system—the organ of balance during movement—is also convergent among ecomorphs, reflecting the shared sensory requirements of their ecological niches. As semicircular canal shape has been shown to reflect different locomotor strategies, we hypothesized that each Anolis ecomorph would have a unique canal morphology. Using three-dimensional semilandmarks and geometric morphometrics, semicircular canal shape was characterized in 41 Anolis species from the Greater Antilles and the relationship between canal shape and ecomorph grouping, phylogenetic history, size, head dimensions, and perch characteristics was assessed. Further, canal morphology of modern species was used to predict the ecomorph affinity of five fossil anoles from the Miocene of the Dominican Republic. Of the covariates tested, our study recovered ecomorph as the single-most important covariate of canal morphology in modern taxa; although phylogenetic history, size, and head dimensions also showed a small, yet significant correlation with shape. Surprisingly, perch characteristics were not found to be significant covariates of canal shape, even though they are important habitat variables. Using posterior probabilities, we found that the fossil anoles have different semicircular canals shapes to modern ecomorph groupings implying extinct anoles may have been interacting with their Miocene environment in different ways to modern Anolis species.
Data from: Integration of molecules and new fossils supports a Triassic origin for Lepidosauria (lizards, snakes, and tuatara)
Background: Lepidosauria (lizards, snakes, tuatara) is a globally distributed and ecologically important group of over 9,000 reptile species. The earliest fossil records are currently restricted to the Late Triassic and often dated to 227 million years ago (Mya). As these early records include taxa that are relatively derived in their morphology (e.g. Brachyrhinodon), an earlier unknown history of Lepidosauria is implied. However, molecular age estimates for Lepidosauria have been problematic; dates for the most recent common ancestor of all lepidosaurs range between approximately 226 and 289 Mya whereas estimates for crown-group Squamata (lizards and snakes) vary more dramatically: 179 to 294 Mya. This uncertainty restricts inferences regarding the patterns of diversification and evolution of Lepidosauria as a whole. Results: Here we report on a rhynchocephalian fossil from the Middle Triassic of Germany (Vellberg) that represents the oldest known record of a lepidosaur from anywhere in the world. Reliably dated to 238--240 Mya, this material is at least 11 million years older than previously known lepidosaur records and is older than some but not all molecular clock estimates for the origin of lepidosaurs. Using RAG1 sequence data from 77 extant taxa and the new fossil specimens two of several calibrations, we estimate that the most recent common ancestor of Lepidosauria lived at least 242 Mya (238--249.5), and crown-group Squamata originated around 193 Mya (176--213). Conclusion: A Early/Middle Triassic date for the origin of Lepidosauria disagrees with previous estimates deep within the Permian and suggests the group evolved as part of the faunal recovery after the end-Permain mass extinction as the climate became more humid. Our origin time for crown-group Squamata coincides with shifts towards warmer climates and dramatic changes in fauna and flora. Most major subclades within Squamata originated in the Cretaceous postdating major continental fragmentation. The Vellberg fossil locality is expected to become an important resource for providing a more balanced picture of the Triassic and for bridging gaps in the fossil record of several other major vertebrate groups.
Data from: Gliding lizards use the position of the sun to enhance social display
Effective communication requires animal signals to be readily detected by receivers in the environments in which they are typically given. Certain light conditions enhance the visibility of colour signals and these conditions can vary depending on the orientation of the sun and the position of the signaller. We tested whether Draco sumatranus gliding lizards modified their position relative to the sun to enhance the conspicuousness of their throat-fan (dewlap) during social display to conspecifics. The dewlap was translucent, and we found that lizards were significantly more likely to orient themselves perpendicular to the sun when displaying. This increases the dewlap's radiance, and likely, its conspicuousness, by increasing the amount of light transmitted through the ornament. This is a rare example of a behavioural adaptation for enhancing the visibility of an ornament to distant receivers.
Data from: Interrogating genomic-scale data for Squamata (lizards, snakes, and amphisbaenians) shows no support for key traditional morphological relationships
Genomics is narrowing uncertainty in the phylogenetic structure for many amniote groups. For one of the most diverse and species-rich groups, the squamate reptiles (lizards and snakes, amphisbaenians), an inverse correlation between the number of taxa and loci sampled still persists across all publications using DNA sequence data and reaching a consensus on the relationships among them has been highly problematic. Here, we use high-throughput sequence data from 289 samples covering 75 families of squamates to address phylogenetic affinities, estimate divergence times, and characterize residual topological uncertainty in the presence of genome scale data. Importantly, we address genomic support for the traditional taxonomic groupings Scleroglossa and Macrostomata using novel machine-learning techniques. We interrogate genes using various metrics inherent to these loci, including parsimony-informative sites, phylogenetic informativeness, length, gaps, number of substitutions, and site concordance to understand why certain loci fail to find previously well-supported molecular clades and how they fail to support species-tree estimates. We show that both incomplete lineage sorting and poor gene-tree estimation (due to a few undesirable gene properties, such as an insufficient number of parsimony informative sites), may account for most gene and species-tree discordance. We find overwhelming signal for Toxicofera, and also show that none of the loci included in this study supports Scleroglossa or Macrostomata. We comment on the origins and diversification of Squamata throughout the Mesozoic and underscore remaining uncertainties that persist in both deeper parts of the tree (e.g., relationships between Dibamia, Gekkota, and remaining squamates; and between the three toxiferan clades Iguania, Serpentes, and Anguiformes) and within specific clades (e.g., affinities among gekkotan, pleurodont iguanians, and colubroid families).
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Allen Brain Atlas
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Annotated Behaviour and Observability Dataset (ABODe)
ABODe is a University of Edinburgh DataShare dataset for behavior classification in group-housed mice using home-cage video, identities, bounding boxes, ground-plate positions, and annotator labels.
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