Search

Lizards exhibit sexual dimorphism in various phenotypic traits and capability performance (e.g. bite force), while the patterns of sexual dimorphism vary among genera and species. The relationship between morphology and function is dynamic, and selective pressures can differentially affect bite performance in different sexes. Here, we analyzed sexual dimorphism in morphological traits and bite force and explored the determinants of bite force in the mountain dragon (Diploderma batangense) from western China. A total of 135 individuals were collected, and nine morphological characteristics and bite force were measured. We found a significant male bias in morphology and bite force performance, with males found to be larger than females in regard to head size, body size, limb length, tail length and bite force, which could be explained by sexual selection. Results also showed that bite force was positively correlated with head size, with the determinant affecting bite force differing between males( mouth length) and females( head width), which may be related to their different roles in reproduction. This study provides a reference for understanding the ecological adaptability of mountain dragons in the field and lays a foundation for revealing the mechanism of bite force variation between the sexes.

Competition between animals for limited resources often involves signaling to establish ownership or dominance. In some species, the defended resource relates to suitable thermal conditions and refuge from predators. This is particularly true of burrow-dwelling lizards such as the Qinghai toad-headed agama (Phrynocephalus vlangalii), which are found on the Tibetan plateau of western China. Male and female lizards occupy separate burrows, which are vital for anti-predator behaviour during warmer months when lizards are active and, crucially, provide shelter from harsh winter conditions. These lizards are readily observed signaling by means of tail displays on the sand dunes they inhabit. Given the selective pressure to hold such a resource, both males and females should exhibit territorial behaviour and we considered this study system to examine in detail how social context influences motion based territorial signaling. We confirmed that territorial signaling was used by both sexes and by adopting a novel strategy that permitted 3D reconstruction of tail displays, we identified significant variation due to social context. However, signal structure was not related to lizard morphology. Clearly, the burrow is a highly valued resource and we suggest that additional variation in signaling behaviour might be mediated by resource quality.

Island species and their ecosystems play an important role in global biodiversity preservation, and many vulnerable island species are conservation priorities. Although insular habitat likely facilitates the species diversification process, it may also aggravate the fragility of these species with high risk of inbreeding. The Shedao pit-viper Gloydius shedaoensis is an island endemic species with an extremely high population density, which has been categorized as vulnerable in the IUCN (International Union for the Conservation of Nature and Natural Resources) Red List. We collected 13,148 SNP (Single Nucleotide Polymorphism) from across its genome and examined its genetic diversity and demographic history. The Shedao pit-viper has a low genetic diversity but shows no sign of inbreeding. Furthermore, population genetic structure analysis, including the neighbor-joining tree, principal coordinate analysis, clustering, and spatial autocorrelation, revealed a general lack of spatial structure. Only the isolation by distance residues suggested a weak patchiness. Overall, the population is nearly panmictic and gene flow is evenly distributed across the island. A large number of individuals, small size of the island, and the lack of population structure likely all contribute to the lack of inbreeding in this species. We also detected signs of male-biased dispersal, which likely is another inbreeding avoidance strategy. Historical demographic analysis suggested that the historical population size and distribution of the species are much larger than their current ones. The multiple transgressive–regressive events since the Late Pleistocene are likely the main cause of the population size changes. Taken together, our results provide a basic scientific foundation for the conservation of this interesting and important species.

The Shedao pit-viper (Gloydius shedaoensis) exhibits an extreme sedentary lifestyle. The island species exclusively feeds on migratory birds during migratory seasons and experiences prolonged hibernation and aestivation period each year (up to eight months). The sedentary strategy reduces energy expenditure, but may trigger a series of adverse effects and the snakes have likely evolved genetic modifications to alleviate these effects. To investigate the genetic adaptations, we sequenced and compared the transcriptomes of the Shedao pit-viper and its closest mainland relative, the black eyebrow pit-viper (G. intermedius). The Shedao pit-viper revealed a low rate of molecular evolution compared to its mainland relative, which is possibly associated with metabolic suppression. Signals of positive selection were detected in two genes related to antithrombin (SERPINC1) and muscle atrophy (AARS). Those genes exert significant functions in thrombosis, inhibiting oxidation and prolonged fasting. Convergent and parallel substitutions of amino acid with two other sedentary vertebrates, which often suggest adaptation, were found in a fatty acid beta-oxidation related gene (ACATA1) and a circadian link gene (KLF10), which regulate lipogenesis, gluconeogenesis, and glycolysis. Furthermore, a circadian clock gene (CRY2) exhibited two amino acid substitutions specific to the Shedao pit-viper and one variant was predicted to affect protein function. Modifications of these genes and their related functions may have contributed to the survival of this island snake species with a sedentary lifestyle and extreme seasonal food availability. Our study demonstrated several important clues for future research on physiological and other phenotypic adaptation.

Island species and their ecosystems play an important role in global biodiversity preservation, and many vulnerable island species are conservation priorities. Although insular habitat likely facilitates the species diversification process, it may also aggravate the fragility of these species with high risk of inbreeding. The Shedao pit-viper

Asian pitviper Gloydius changdaoensis is a coastal species, distributed in Shandong province, China. In this study, we successfully sequenced the mitochondrial genome of one individual of G. changdaoensis. The complete mitochondrial genome is circular molecular with 17,224 bp, containing an origin of light-strand replication (OL), two non-coding control regions (CRs), and 37 classical genes of vertebrate, which contain 13 protein-coding genes (PCGs), 2 ribosomal RNA genes, and 22 transfer RNA genes. A Bayesian phylogenetic tree using the complete mitochondrial genomes of all viper species available showed a consistent result with previous studies.

Background Gut and oral microbial communities are complex and play a key role in their co-evolution with their hosts. However, little is understood about the bacterial community in lizards. In this study, we first investigated the gut and oral bacterial community in Diploderma splendidum from Sichuan Province, China. Metagenomic analysis of feces and oral cavity samples showed distinct differences between Diploderma splendidum and Liolaemus parvus, and L. ruibali and Phymaturus williamsi species. Results Bacteridetes, Firmicutes, Proteobacteria and Fusobacteria were the most abundant phyla in fecal samples. However, the composition of the gut bacterial community of insectivorous lizards (Diploderma splendidum) exhibited unique abundance of phyla Proteobacteria and Chlamydiae when compared with L. parvus, L. ruibali and P. williamsi. Furthermore, Proteobacteria were abundant in oral cavity samples, followed by Actinobacteria, Chlamydiae and Firmicutes. Most striking was that the phylum Chlamydiae was most common in the oral cavity of Diploderma splendidum, when compared with a carnivorous lizard (Varanus komodoensis). In addition, more than 26 bacterial species were detected in the gut and/or oral cavity that were identified as potential human pathogens. Conclusions In this study, metagenomic analysis was carried out to reveal the gut and oral microbiomes, which brought new insight into the complex bacterial community and ecology in Diploderma splendidum.

Determining the susceptibility of species to changing thermal niches is a major goal for biologists. In this paper we develop an eco-physiological model of extinction risk under climate change premised on behavioral thermoregulation. Our method downscales operative environmental temperatures, which restrict hours of activity of lizards, hr , for present-day climate (1975) and future climate scenarios (2070). We apply our model using occurrence records of 20 Phrynocephalus lizards (or taxa in species complexes) drawn from literature and museum records. Our analysis is phylogenetically informed, because some clades may be more sensitive to rising temperatures. The limits for computed hr predict local extirpations among Phrynocephalus lizards at continental scales and delineate upper boundaries of thermal niches as defined by Extreme Value Distributions. Under the 8.5 Representative Concentration Pathway scenario, we predict extirpation of 64% of local populations by 2070 across 20 Phrynocephalus species, and 12 are at high risk of total extinction due to thermal limits being exceeded. In tandem with global strategies of lower CO2 emissions, we propose regional strategies for establishing new national parks to protect extinction-prone taxa by preserving high-elevation climate refugia within existing sites of species occurrence. We propose that evolved acclimatization - maternal plasticity - may ameliorate risk, but is poorly studied. Previous studies revealed that adaptive maternal plasticity by thermoregulating gravid females alter progeny thermal preferences by ±1 °C. We describe plasticity studies for extinction-prone species that could assess whether they might be buffered from climate warming - a self-rescue. We discuss an epigenetic framework for studying such maternal-effect evolution.

Female–female aggression and its functions are poorly understood compared with male–male aggression. Here, we examined the role of female–female aggression in mate defence in an Asian agamid lizard, Phrynocephalus vlangalii, in which male neighbours are valuable to females in both mating success and resource defence. We provided three social contexts by pairing a resident female with either a neighbour male, unfamiliar male or unfamiliar female, then introduced a tethered unknown female (intruder). We carried out our experiments during and outside the mating season to test the links between female–female aggression and mate defence. The aggressive responses of resident females in these different social contexts were compared by quantifying variation in their territorial displays. Resident females were faster to display to the intruder in the presence of a neighbour male compared with both the unfamiliar male and female. We also found that female lizards signalled faster in the presence of the neighbour male than the other contexts, but only during the mating season. To separate the effects of familiarity from those of sex, we carried out a second experiment in which we paired a resident female with a neighbour male or neighbour female, before introducing a tethered unfamiliar female. In this experiment, resident females responded sooner to intruder females when paired with the neighbour male, although signalling speeds were equivalent. Taken together, our results suggest female–female aggression is used for both resource and mate defence, and so might be under direct selection. Our study highlights that female aggression more broadly requires further work.

Female-female aggression and its effect on fitness are poorly understood compared to male-male aggression. We quantified female-female aggression in the viviparous toad-headed agama, Phrynocephalus vlangalii, and tested the mate limitation and resource competition hypotheses, to explain the driving forces behind heightened female-female aggression. We established populations in outdoor enclosures and separately manipulated mate and food availability while quantifying aggressive interactions between known females. Female mass and offspring quantity and quality were monitored for 2 years and used as an index of female fitness. Interestingly, female-female aggression was highest outside the mating season, when females were pregnant. Also, male availability did not significantly influence female-female aggression. Consequently, we found no evidence in support of the mate limitation hypothesis. Female-female aggression, however, was greatest during periods of low-food availability. Greater food availability did have positive fitness consequence for females: high-food treatment females were more likely to gain mass and give birth than females from the low-food treatment, and offspring from high-food treatment females were more likely to survive the first winter. However, we did have an effect of year: female mass was negatively associated with female-female aggression in year 1 but positively associated in year 2, although the association was not significant. The same pattern appeared in the association between offspring sprint speed and female-female aggression: higher levels of female-female aggression in year 1 were associated with slower offspring, while in year 2, higher female-female aggression was associated with faster offspring. Overall, our results demonstrate a link between female-female aggression and competition for resource (food) and highlight the potential importance of female aggressive behavior as a mechanism that influences female fitness. Male-male contest competition has been a cornerstone of sexual selection theory for decades because dominant males can control more space and access to females. Conversely, female aggression is poorly understood and sometimes considered a paradox, especially in species lacking parental care. We tested whether female-female aggression in the viviparous lizard P. vlangalii is best explained by competition for males (mate limitation hypothesis) or competition over food (food limitation hypothesis). Interestingly, female aggression peaks after mating, while females are still pregnant. Heightened aggression at this time supports the food limitation hypothesis because any advantage females have in terms of access to resources will benefit offspring born into her home range. Likewise, access to additional food resources may improve female survival and future reproductive investment through greater energy storage.

Viviparous lizards living in cold climate of high altitude often exhibit atypical reproductive cycles, in which mating and fertilization occur synchronously and annually with parturition occurring at the end of the year. Nevertheless, detailed case studies on atypical reproductive cycles are few. Using anatomical data combined with behavioral observations, we examined the reproductive cycle of a common Asian agamid, Phrynocephalus vlangalii, from a high‐elevation area in Sichuan, China. Male spermiation of P. vlangalii occurred in May, and spermatogenesis began in June and reached a maximum in October. For females, ovulation and fertilization occurred in May, and females developed gestation and pregnancy in 3 months from June to August, without vitellogenesis during this period. Females gave birth synchronously in late August, then vitellogenesis began and lasted until May of the next year. All adult males and females were synchronized in the same reproductive condition each month. The synchronous and annual reproductive cycle of P. vlangalii clearly represents an atypical cycle. The male courtship and mating behaviors were concordant with gonadal cycle and mainly happened in May and June. Despite the short growth period for neonates, they had a high over‐winter survival rate of 84.4%, suggesting that autumn parturition did not generate high costs to this reproductive cycle. We propose that the high over‐winter survival rate of neonates is likely linked with female delayed sexual maturity, female asynchronous vitellogenesis and gestation, large relative clutch mass (RCM), and adult‐offspring burrow sharing behavior during hibernation.

The ecosystem of the Tibetan Plateau is extremely fragile, and a careful and long-term monitoring program is essential with the global climate changes and rapid social development. Phrynocephalus vlangalii is an excellent environmental indicator species, and therefore we developed twenty-five novel microsatellite DNA makers for it. All loci were polymorphic, with number of alleles ranging from 2 to 9. The observed and expected heterozygosity of these loci ranged from 0.00 to 0.85 and from 0.13 to 0.80, respectively. Fifteen loci were found to be significantly deviated from Hardy–Weinberg equilibrium and all loci were in linkage equilibrium. Seven closely-related Phrynocephalus species were tested for cross-species amplifiability of those loci; all loci had higher cross-amplification rate, with 17 being successfully amplified in more than three species. These markers will provide useful tools for monitoring the influence of social development in the Tibetan Plateau.

In lizards, males are predicted to sprint faster and run for longer than females by virtue of higher testosterone levels and differences in morphology. Consequently, escape behaviour is also predicted to be associated with sex and locomotor performance, yet these links have rarely been explored. Here, we tested whether escape behaviour is associated with locomotor performance in the toad-headed agama, Phrynocephalus vlangalii, and whether it is sex-dependent. This species is also characterized by elaborate tail displays, which we examined as a potential pursuit-deterrent signal. Tail waves were performed by a very small proportion (2/58, 3 %) of individuals during predatory trials, suggesting that tail signalling functions exclusively in a social context. To understand the relationships between sex, escape behaviour and performance, we first measured escape behaviour (flight initiation distance, flight distance—measured differently compared to previous studies of lizard escape behaviour, and refuge use) in the field before measuring maximal sprint speed and endurance on the same individuals in the laboratory. Flight initiation distance did not differ between the sexes and was unrelated to performance capacity (maximal endurance and sprint speed) but was positively related to body size with larger individuals fleeing earlier. Males fled farther than females, but flight distance was also unrelated to either endurance or sprint speed. Interestingly, faster females were less likely to enter a refuge than slower females, whereas sprint speed and the probability of taking refuge were unrelated for males. Our results suggest that when males and females are not obviously sexually dimorphic, they are more likely to overlap in escape tactics.

Summary information of digital gene expression profiles. (DOCX 84Â kb)