White’s Skinks, Liopholis whitii (Lacépède 1804) are widely distributed throughout rocky habitats of temperate south-eastern Australia, with a highly disjunct population occurring in Mutawintji National Park in arid far western New South Wales. Based on an analysis of genome-wide nuclear single-nucleotide polymorphisms (SNPs) and an assessment of variation in morphology, we provide an appraisal of the group’s evolutionary history and re-evaluate the taxonomic status of candidate lineages. We reveal the presence of three major genetic lineages, including two lineages from temperate south-eastern Australia, and another representing the isolated arid population from Mutawintji National Park. We herein apply the name Liopholis whitii to the temperate “southern” lineage which occurs in South Australia, Victoria and Tasmania; resurrect the name Liopholis compressicauda (Quoy & Gaimard 1824) for the temperate “northern” lineage from southern Queensland, New South Wales, Australian Capital Territory and north-eastern Victoria; and describe the arid lineage from Mutawintji National Park as Liopholis mutawintji sp. nov. Liopholis mutawintji sp. nov. is of particular conservation concern and likely eligible for listing as Critically Endangered under multiple IUCN Red List Criteria.

The neurotransmitters vasotocin, oxytocin, dopamine, and serotonin are widely involved in vertebrate social behavior, and changes in their abundance and distribution in the brain have been linked to the evolution of complex sociality. Reptiles provide an excellent system in which to investigate the neural mechanisms of social living. Using immunohistochemistry, we compare distributions of these transmitters in two skinks differing primarily in social ecology: the family-living Liopholis whitii and the solitary Eulpamrus quoyii. We describe patterns of immunopositive signal for both cell bodies and fibers across the entire brain (excluding the olfactory bulbs). In both species, vasotocin and oxytocin were found in the preoptic area, paraventricular nucleus, supraoptic nucleus, dorsomedial hypothalamus, and supraoptic decussation, as well as surrounding the lateral forebrain bundle. Tyrosine hydroxylase (a marker for dopamine) was found in the paraventricular organ nucleus, substantia nigra, and ventral tegmental area, and serotonin was found in the raphe nuclei and superior reticular field. We found novel oxytocin cell groups in the dorsomedial hypothalamus and cerebellum of L. whitii, and novel serotonin signal in the red nucleus of E. quoyii. Immunopositive signals found only in L. whitii also include vasotocin in the ventral tegmental area, tyrosine hydroxylase in the interpeduncular nucleus, and serotonin in the suprachiasmatic nucleus. The qualitatively greater abundance of these transmitters in the family-living L. whitii suggests that these molecules may have played an important role in the evolution of social behavior in these skinks and provides a foundation for broader comparisons across the social skinks.

Genetically determined color morphs are found in many animals. Polymorphism can be maintained by social selection if competitive interactions allow each morph to increase in frequency when rare. This reliance on negative frequency-dependent selection should make color polymorphism vulnerable to the appearance of novel phenotypes that disrupt competitive interactions among morphs. We show that the origin and adaptive spread of a sexually selected syndrome in common wall lizards (Podarcis muralis) selectively eliminates alleles coding for alternative color morphs that have been maintained for millions of years. The results demonstrate how the arrival of a novel phenotype can disrupt balancing selection, providing a link between rapid phenotypic evolution and the loss of color polymorphisms.

Parent-offspring associations provide the basis for more complex care and breeding systems. One proximate mechanism by which parental behavior is facilitated across animal taxa is via nonapeptide hormones such as arginine vasotocin (AVT). However, existing research largely comes from obligately social species, and whether such mechanisms are conserved in social systems where care is facultative remains unclear. Here, we used a facultatively family living skink, Liopholis whitii, to test the role of AVT in mediating 2 key parental behaviors: parent-offspring associations (measured by proximity between mothers and offspring) and maternal aggression (in response to a conspecific model). We found that increasing AVT via intraperitoneal injection led to more time spent in closer proximity between mother and offspring. Conversely, a decrease in AVT signaling (using an AVT receptor antagonist) resulted in a reduction in the time spent in closer proximity. We also found that these effects caused by increased AVT signaling persisted for several weeks, suggesting a potential organizational effect of AVT on the mother-offspring relationship. Contrary to our predictions, we found no effect of AVT manipulations on maternal aggression, suggesting that AVT may have been de-coupled from its usual role as a moderator of aggression. These results support the idea that AVT may be a mechanism involved in governing parental behavior in this system, and as such, could have played a key role in the repeated evolution of group living.

The way organisms perceive the world influences their evolution. Many animals detect ultraviolet (UV) light invisible to humans, creating sensory contexts that alter the selective landscape for coloration. Here, we dissected the molecular basis of a UV-reflecting color morph in common wall lizards, uncovering its association with a noncoding region upstream of the transcription factor PAX7. Our results suggest that variation at this locus alters dermal architecture by modifying the cellular composition, exposing structures within specialized cells that generate UV structural coloration. We further demonstrate that the PAX7 locus acts epistatically on other color genes to suppress pigment deposition, revealing a genetic interaction between pigmentary and structural pathways that underlie color production. Across populations, the frequency of the UV morph was not predicted by environmental variation, arguing against climate-driven selection. Inferred frequencies of the UV-associated allele across sampled populations exhibited weaker spatial structure than expected from genome-wide variation, suggesting this polymorphism may be maintained by balancing selection. Our findings reveal mechanisms of phenotypic evolution beyond human perception and a genetic link between pigmentary and structural coloration.

The Tiliquini skinks are a clade of lizards that include multiple species that live in long-lasting, territorial groups. Memberships among group-living species range from simple nuclear families to larger, more complex groups containing multiple generations of offspring and sometimes, unrelated adults. We detail the factors that favour the formation of societies in one model species, the White's skink, Liopholis whitii, in which groups typically consist simply of a nuclear family (parents plus one generation of offspring), although some groups expand into what can be called incipient societies in that they can contain multiple generations of offspring and unrelated adults. Conversely, two other species (Cunningham's skink, Egernia cunninghami, and the gidgee skink, Egernia stokesii) live in much larger groups and their behaviour is more consistent with being societal. We suggest that the mechanism whereby individuals can gain entrance into a new group is through repeated exposure at the periphery of the group's territory, which in turn generates familiarity and tolerance. We argue that lizards provide a valuable model for understanding the origins and maintenance of societal formation in vertebrates. (c) 2025 The Author(s). Published by Elsevier Ltd on behalf of The Association for the Study of Animal Behaviour. This is an open access article under the CC BY license (http://creativecommons.org/licenses/ by/4.0/).

Abstract Climate change can threaten population viability by disrupting sex ratios in species whose sex is influenced by temperature. While species with sex chromosomes were historically considered immune, in some species, temperatures can override genetic sex determination via sex reversal, leaving them vulnerable to climate-driven sex ratio shifts. The Tasmanian spotted snow skink ( Carinacincus ocellatus ), a viviparous reptile with an XX/XY system, provides a compelling case study. While laboratory studies demonstrated that extreme thermal conditions induce female-to-male sex reversal (XX males), its occurrence in the wild remains unexplored, limiting our understanding of actual climate impacts. Integrating 23 years of phenotypic and genetic sexing data across two climatically distinct populations, we provide the first evidence of sex reversal in a wild viviparous reptile. XX reversal occurred in both populations, affecting up to 23.5% of XX births in the warmer population, and was associated with colder minimum daily temperatures. Despite high birth rates in some years, sex-reversed adults were rare. We also identified putative XY females, suggesting bidirectional sex reversal and reinforcing the extreme plasticity of reptilian sex determination. Ultimately, sex reversal could act as an evolutionary trap, potentially compromising population viability as climate instability increases.

Increasing resource demand, desire to sequester atmospheric carbon, and conservation goals are driving a need for forests to be managed more effectively in the face of numerous challenges. One such challenge is damage perpetrated by browsing mammals, which can cause substantial financial and ecological impacts. Current practices focus on lethal control measures for mitigating mammal browsing damage, however stakeholder pressure is calling for a transition to non-lethal alternatives. Little is known about the relative efficacy of different non-lethal control methods for mitigating browsing damage by mammals other than deer. Using a multilevel meta-analytical framework across 1,908 effect sizes, we investigate the relative efficacy and longevity of different non-lethal control methods implemented against a broad suite of browsing mammals across different spatial scales. We found that tree guards, repellents and exclusion fencing all significantly reduce mammal browsing damage and retain their effect for long periods. There was, however, substantial variation in efficacy within individual control strategies highlighting the importance to forest managers of selecting the correct method from within the broad strategies we identified. We then discuss other factors to consider when implementing non-lethal mammal browsing control so that forest managers are well informed when implementing a control strategy.

Exposure to stressors and associated hormones during development can significantly affect offspring phenotype, including social and philopatric behaviour, but these effects can be mediated by the postnatal social environment ('social buffering'). While the effects of social buffering are well established for complex social behaviours-such as parental provisioning, grooming or cooperative care-the role of social buffering for simpler social interactions-such as parental tolerance of offspring-remains less understood. Here we used the facultatively social viviparous lizard, Liopholis whitii, to test the following: (i) the effects of elevated maternal glucocorticoid levels during gestation on offspring mass, growth, dispersal and social interactions after birth; and (ii) whether these effects are mediated by postnatal mother-offspring association. We conducted a factorial experiment in which pregnant lizards were given thrice-weekly doses of a glucocorticoid hormone (corticosterone) or a control during gestation. Their offspring were then raised either alone or with their mother for 3 weeks. We subsequently released mothers and offspring in large semi-natural enclosures and quantified offspring mass and social/exploratory behaviour. There were persistent negative effects of prenatal glucocorticoid exposure on offspring growth. We also observed lasting effects of prenatal glucocorticoid exposure on social behaviour: offspring from glucocorticoid-treated mothers had stronger social associations with other individuals, including with their mother and siblings, compared to offspring from control mothers. Association with their mother early in life did not mediate the effects of prenatal glucocorticoid exposure on offspring phenotype. These effects demonstrate that maternal stress can be an important mediator of variation in social behaviour in lizards, even overriding the influence of the social environment in the early postnatal period. This has potential implications for understanding how social groups form and are maintained.

Kin recognition, the ability to identify genetic relatives, relies on familiarisation for the creation of recognition templates. During development, parent and embryo(s) are exposed to chemical, auditory, and tactile cues that can communicate reliable genetic information. We discuss how these cues can have organisational effects during a time of heightened phenotypic sensitivity, creating postnatal kin preferences. As familiarisation is often determined by the prenatal social environment, we argue that reproductive traits that alter the social context of the prenatal environment, such as reproductive mode, could facilitate the evolution of kin recognition. Furthermore, we outline how these effects of prenatal familiarisation can extend beyond kin recognition and play a pivotal role in the emergence and evolution of complex social behaviours.

Understanding the responses of organisms to environmental change is critical to tackling the grand challenges of 21st century biology. Fields such as ecophysiology and ecology have embraced these challenges and “re-invented” themselves in part by shifting the scale of scientific enquiry and utilizing large-scale comparative approaches. Behavioural research has not yet realized this potential to the same extent. In this paper, we argue that adopting a trait-based approach at large spatial, temporal and taxonomic scales can advance the field of behavioral ecology and address emerging questions in biology. We surveyed the literature in relevant ecology and behavior journals between 1981 and 2020 and found that ecological journals have changed markedly over time, specifically in their focus on understanding interspecific trait variation at broad taxonomic, spatial and temporal scales. This pattern is not apparent for animal behavior, where intra-specific and often intra-population scale of scientific enquiry has mostly been the focus over the last four decades. We argue that behavioral plasticity can be a critical first response to environmental change that might buffer or even lower the risk of extinction. To estimate the capacity of populations or species to respond to change behaviorally, we propose a comparative approach- spatially, temporally or taxonomically- that systematically captures variation in key traits with broad implications for conservation and community ecology. Further, we provide guidance in the methods and resources required to apply a trait-based approach to animal behavior.

BACKGROUND:The Earth Hologenome Initiative (EHI) is a global endeavor dedicated to revisit fundamental ecological and evolutionary questions from the systemic host-microbiota perspective, through the standardized generation and analysis of joint animal genomic and associated microbial metagenomic data. RESULTS:The first data release of the EHI contains 968 shotgun DNA sequencing read files containing 5.2 TB of raw genomic and metagenomic data derived from 21 vertebrate species sampled across 12 countries, as well as 17,666 metagenome-assembled genomes reconstructed from these data. CONCLUSIONS:The dataset can be used to address fundamental questions about host-microbiota interactions and will be available to the research community under the EHI data usage conditions.

The joint expression of particular colors, morphologies, and behaviors is a common feature of adaptation, but the genetic basis for such “phenotypic syndromes” remains poorly understood. Here, we identified a complex genetic architecture associated with a sexually selected syndrome in common wall lizards, by capitalizing on the adaptive introgression of coloration and morphology into a distantly related lineage. Consistent with the hypothesis that the evolution of phenotypic syndromes in vertebrates is facilitated by developmental linkage through neural crest cells, most of the genes associated with the syndrome are involved in neural crest cell regulation. A major locus was a ~400-kb region, characterized by standing structural genetic variation and previously implied in the evolutionary innovation of coloration and beak size in birds. We conclude that features of the developmental and genetic architecture contribute to maintaining trait integration, facilitating the extensive and rapid introgressive spread of suites of sexually selected characters.

Telomeres, the repetitive DNA regions that protect the ends of chromosomes, and their shortening have been linked to key life history trade-offs among growth, reproduction and lifespan. In contrast to most endotherms, many ectotherms can compensate for telomere shortening throughout life by upregulation of telomerase in somatic tissues. However, during development, marked by rapid growth and an increased sensitivity to extrinsic factors, the upregulation of telomerase may be overwhelmed, resulting in longterm impacts on telomere dynamics. In ectotherms, one extrinsic factor that may play a particularly important role in development is temperature. Here, we investigated the influence of developmental temperature and sex on early -life telomere dynamics in an oviparous ectotherm, Lacerta agilis. While there was no effect of developmental temperature on telomere length at hatching, there were subsequent effects on telomere maintenance capacity, with individuals incubated at warm temperatures exhibiting less telomere maintenance compared with cool -incubated individuals. Telomere dynamics were also sexually dimorphic, with females having longer telomeres and greater telomere maintenance compared with males. We suggest that selection drives this sexual dimorphism in telomere maintenance, in which females maximise their lifetime reproductive success by investing in traits promoting longevity such as maintenance, while males invest in short-term reproductive gains through a polygynous mating behaviour. These early -life effects, therefore, have the potential to mediate life-long changes to life histories.

Identifying the environmental factors associated with group living is important for understanding how social systems originate, persist and diversify. In endothermic birds and mammals, living in social groups is associated with habitat constraints and harsh climatic conditions. We use phylogenetic comparative analyses to test whether climate and habitat have played similar roles in the evolution of social grouping in a globally distributed clade of ectothermic vertebrates, lizards (Nspecies = 1696). Social grouping was strongly associated with cool, dry climates across the lizard phylogeny. However, this climatic signature arose indirectly, by association with live birth (common in cool climates) and a reliance on rock crevices (common in dry climates), traits which increase parent-offspring associations and reduce offspring dispersal. In contrast, direct effects of cool temperature on the evolution of social grouping were marginal and restricted to live bearing species. Our results demonstrate that relationships between climate and sociality may result from climatic adaptations that go on to promote the emergence of grouping behaviour.### Competing Interest StatementThe authors have declared no competing interest.

AimSquamate fitness is affected by body temperature, which in turn is influenced by environmental temperatures and, in many species, by exposure to solar radiation. The biophysical drivers of body temperature have been widely studied, but we lack an integrative synthesis of actual body temperatures experienced in the field, and their relationships to environmental temperatures, across phylogeny, behaviour and climate.LocationGlobal (25 countries on six continents).TaxaSquamates (210 species, representing 25 families).MethodsWe measured the body temperatures of 20,231 individuals of squamates in the field while they were active. We examined how body temperatures vary with substrate and air temperatures across taxa, climates and behaviours (basking and diel activity).ResultsHeliothermic lizards had the highest body temperatures. Their body temperatures were the most weakly correlated with substrate and air temperatures. Body temperatures of non-heliothermic diurnal lizards were similar to heliotherms in relation to air temperature, but similar to nocturnal species in relation to substrate temperatures. The correlation of body temperature with air and substrate temperatures was stronger in diurnal snakes and non-heliothermic lizards than in heliotherms. Body-substrate and body-air temperature correlations varied with mean annual temperatures in all diurnal squamates, especially in heliotherms. Thermal relations vary with behaviour (heliothermy, nocturnality) in cold climates but converge towards the same relation in warm climates. Non-heliotherms and nocturnal species body temperatures are better explained by substrate temperature than by air temperature. Body temperature distributions become left-skewed in warmer-bodied species, especially in colder climates.Main ConclusionsSquamate body temperatures, their frequency distributions and their relation to environmental temperature, are globally influenced by behavioural and climatic factors. For all temperatures and climates, heliothermic species' body temperatures are consistently higher and more stable than in other species, but in regions with warmer climate these differences become less pronounced. A comparable variation was found in non-heliotherms, but in not nocturnal species whose body temperatures were similar to air and substrate irrespective of the macroclimatic context.

Family life often involves interactions between individuals who have different fitness goals, leading to conflict. Resolution of this conflict is key for the stabilisation of family life. Here, we used a lizard, Liopholis whitii , that lives in facultative family groups to characterise the nature and extent of sibling conflict and test the role that individual and litter characteristics play in shaping conflict between family members. We found significant variation in conflict between family groups, specifically in relation to siblings. In approximately half of the litters, siblings were aggressive towards one another, while in the other half of litters, there was no aggression observed between siblings. There were no differences between aggressive and non-aggressive litters in the key factors predicted to mediate conflict, including sex, offspring size, or litter size. However, in aggressive litters, the maximum amount of within-litter conflict decreased with an increase in the spread between births of siblings. First-born offspring were significantly more likely to be aggressive towards their siblings compared to second and third born offspring. While one offspring was usually the target of that aggression, we found no evidence that any individual-level factor predicted who received aggression. In aggressive litters, aggressive offspring spent a greater amount of time with their mother compared to non-aggressive offspring. Similar asymmetries in the amount of time offspring spent with their mother between siblings were also observed in non-aggressive litters. Combined, our results suggest that birth order is the main driver of sibling conflict in aggressive litters in this facultatively social lizard species, suggesting that birthing asynchrony may provide females with a mechanism to manage conflict. Significance statement Conflict is a ubiquitous aspect of family life; it occurs between adults, between parents and offspring as well as between siblings. We show that the extent of conflict between siblings varies considerably within and between families in a lizard that exhibits prolonged associations between parents and offspring. We found no effects of offspring sex or size on within or between litter conflict. Instead, the number of days that passed between the birth of offspring appears to be the main factor that influences how much conflict there is between siblings. Furthermore, birth order was the main factor predicting which offspring was dominant. Combined this suggests that birthing asynchrony, the ability of females to spread out births across multiple days, may play a crucial role in the management of conflict in this system. As the moderation of conflict is crucial for the stabilisation of family life, these results provide important insights into the early evolution of social life.

Common wall lizards (Podarcis muralis) in Italy show a striking variation in body coloration across the landscape, with highly exaggerated black and green colors in hot and dry climates and brown and white colors in cool and wet climates. Males are more intensely colored than females, and previous work has suggested that the maintenance of variation in coloration across the landscape reflects climatic effects on the strength of male-male competition, and through this sexual selection. However climatic effects on the intensity of male-male competition would need to be exceptionally strong to fully explain the geographic patterns of color variation. Thus, additional processes may contribute to the maintenance of color variation. Here we test the hypothesis that selection for green and black ornamentation in the context of male-male competition is opposed by selection against ornamentation because the genes involved in the regulation of coloration have pleiotropic effects on thermal physiology, such that ornamentation is selected against in cool climates. Field observations revealed no association between body coloration and microhabitat use or field active body temperatures. Consistent with these field data, lizards at the extreme ends of the phenotypic distribution for body coloration did not show any differences in critical minimum temperature, preferred body temperature, temperature-dependent metabolic rate, or evaporative water loss when tested in the laboratory. Combined, these results provide no evidence that genes that underlie sexual ornamentation are selected against in cool climate because of pleiotropic effects on thermal biology.

Quantifying how variable temperature regimes affect energy expenditure during development is crucial for understanding how future thermal regimes may impact early life survival and population persistence. Developmental Cost Theory (DCT) suggests that there is an optimal temperature (T opt ) that minimises energy expenditure during development (the “cost of development”). Exposure to fluctuating temperatures around an average of T opt are anticipated to increase either development time or metabolic rate. As a result, embryos will rapidly deplete yolk reserves, and consequently hatch at a smaller size or with less residual yolk to support postnatal survival and growth. Here, we studied total embryonic energy expenditure (development time and rate of CO 2 production) and conversion of yolk into tissue in common wall lizards ( Podarcis muralis ) under three incubation treatments anticipated, based on DCT, to increase the cost of development: no variance (T opt constant, 24 °C), low variance (22 – 26 °C), and high variance (18 – 30 °C). As predicted, we found that increasing variance around T opt increased the cost of development, despite reducing time to hatching. As a consequence, embryos on average hatched with 59% lower residual yolk reserves under high variance versus constant incubation temperatures. Our results highlight how the relative temperature sensitivities of development time and metabolic rate determine the cost of development, which in turn may predict the ability of egg-laying ectotherms to persist in variable environments. We show that DCT can provide a mechanistic framework for understanding the widespread, but often seemingly idiosyncratic, effects of fluctuating incubation temperatures on hatchling tissue and residual yolk mass.