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Territoriality evolves when the benefits gained from exclusive access to limited resources exceed the costs of defence. Sometimes animals evolve distinct morphs, that may reflect different capability, and in some territorial species of lizards the polymorphism is associated to alternative strategies, both for reproductive efficiency and territorial dominance. It is known that normally larger males are more aggressive and are able to defend a larger area and for longer than small males; in fact this dynamic is widespread in many animal species including the genus Podarcis. The aim of our study was to test which factors determine the outcome of fighting in the strongly territorial Italian ruin lizard, Podarcis siculus, using two types of contests: (1) resident versus intruder and (2) in a neutral arena. Furthermore, because these lizards are characterized by strong ventral colour variability, usually restricted to jaws and throat, we wanted to investigate if coloured lizards have higher chances at winning than white lizards. The results showed that the fight's result was significantly influenced by the state of residence, while the colour had no effect; instead, the snout to vent length difference between opponents had significant influence on the outcome in the neutral arena. Our results suggest that, in this lizard, both the size and the state of residency, no matter of colour, play an important role to determine the outcome of a fight, however, highly depending on the contest. We think that P. siculus should be object of future studies, focusing on behavioural and ecological aspects, even considering the occurrence of different colours within and among populations.

In the context of the immunocompetence handicap hypothesis, we explored how differences in parasite load affect the way in which sexual ornaments codify information about individual quality. We studied variation in sexual signals in two Iberian populations of the lizard Psammodromus algirus, a species in which sexually active males display a red head coloration. In one population, males were free of tick nymphs, whereas in the other one all males were tick-infested (mean of 12.7 tick nymphs/individual).At the onset of the breeding season, the red-coloured surface was larger in the non-parasitized population than in the parasitized one, whereas the opposite was true for colour saturation. We experimentally simulated a bacterial infection (by intraperitoneal injection of lipopolysaccharide) to examine the effects of immune activation on the expression of this sexual ornament. In the non-parasitized population, our treatment caused a reduction in the red-coloured surface of experimental males, whereas in the parasitized population it caused a decrease in colour saturation. In the parasitized population, males that displayed sexual coloration were larger, and had fewer parasites, than uncoloured ones, and inflammatory response to lipopolysaccharide injection in the palm of the hind paw was negatively correlated with colour saturation, but not with colour extension. Thus, we suggest parasites not only constrained the expression of sexual ornaments, but they also changed the signal properties that conveyed useful information about the quality of their bearers.

Imperfect detection of individuals within an animal population can bias estimates of abundance and other population metrics. However, detectability may be improved by timing surveys with conditions that increase detection among individuals of the population. We explored the weather conditions that promote surface activity in a burrowing desert lizard, Slater's skink Liopholis slateri, with the aim of increasing detectability in observational surveys for this endangered species. We matched repeated count data (n = 126) of individuals within a population of Slater's skink sampled across four survey years with corresponding weather observations. We used classification and regression tree (CART) models to determine the environmental conditions that promoted high skink counts, and by inference high levels of surface activity. We also investigated how individual activity patterns varied over a day–night cycle through the course of a survey year using remote infrared cameras at burrow entrances set to capture images every 30 min. We found that two weather variables, air temperature and humidity, influenced activity levels, but there was no consistent single covariate, or set of covariates that explained surface activity. Variation in results of analysis between morning and evening datasets suggests that lizards respond to different weather conditions at different times of the day. We also found evidence of previously unreported nocturnal activity during the hottest months of the year.

Juveniles of numerous lizard species have a vividly blue-coloured tail that likely serves to deflect predator attacks toward the autotomizable tail rather than the lizard's body. The shades of blue colour in the tails of juvenile Plestiodon latiscutatus lizards vary across populations, most notably among those island populations with different predator assemblages. Here, we determine if this intraspecific variation is associated with the differences in colour vision capabilities of lizard predator species. If associated, it would be evidence for local adaptation of tail colour phenotype – natural selection is maximizing the conspicuousness of the tail to the dominant predator species to increase the chance of successfully deflecting attacks. We also use transmission electron microscopy (TEM) to determine the proximate cellular mechanisms that produce the shades of blue in different populations. We revealed that lizard tails with vivid blue reflectance evolved in communities with either weasel or snake predators, two groups of animals with the ability to detect blue wavelengths. However, lizard tail UV reflectance was much higher in populations with only snake predators; that snakes can detect UV, yet weasels cannot, suggests that high UV reflectance is an adaptation to increase tail conspicuousness specifically to snake predators. Finally, a cryptic brown tail evolved independently on the islands where birds are the primary lizard predator. We suggest that because birds have keen visual acuity; a brown, camouflaged phenotype is more advantageous. We also determined through TEM that the thickness of light reflecting platelets in iridophores, and densities of iridophores and xanthophores, predicted the wavelengths and intensity of light reflected by the lizard tail. For example, blue coloration was produced by selective reflection of short wavelengths of light by the thin light reflecting platelets of the iridophore. Greater iridophore density increased light reflectance, while greater xanthophore density decreased light reflectance.

Due to their particular phylogenetic position and biological characteristics, squamate reptiles and, in particular, snakes are becoming an increasingly important model for fields such as evolutionary biology, molecular ecology and adaptation. Recently, during a study to analyze the evolutionary history of European whip snakes, we found a LINE1 (L1)-like sequence (GenBank accession no. LM644476), herein called TRL1L, and while there are data on the abundance of L1 in snakes, their genomic and chromosome localization is still largely unexplored. We therefore performed a study to obtain information on TRL1L abundance, distribution and conservation in snake species, belonging to the Colubridae, Lamprophiidae and Viperidae families, using quantitative dot-blot and fluorescence in situ hybridization (FISH). TRL1L showed a high identity with homologous segments of L1s of lizards the Anolis carolinensis and Lacerta agilis and the zebrafish Danio rerio. The discovered sequences are truncated L1 elements which occur with a low copy number, about 0.1% of the genome of the species studied. This evidence suggests that L1 retroposons have a similar landscape in lizard and snake genomes, probably because similar processes limited L1 distribution in their genomes. TRL1L showed a non-random chromosome distribution pattern. It was scarcely located on autosomes and on the euchromatic W chromosome of Cerastes vipera, while mostly found on the heterochromatic W chromosome of Hierophis carbonarius and Elaphe quatuorlineata. Our data support the hypothesis that a ‘purifying selection’ against the accumulation of L1 elements takes place in recombining regions and highlight the possible role of these elements in the differentiation processes of the snake heterochromatic W chromosome. Interestingly, the preferential distribution of TRL1L on the heterochromatic W chromosomes of the studied snakes appears to be similar to that observed in mammals for L1 accumulation on differentiated Y chromosomes. This finding suggests that a convergent process may have taken place in the differentiation of vertebrate heterochromatic sex chromosomes

The pace of new reptile species descriptions, especially of new lizard descriptions, is rapidly increasing. The number of recognized lizard species has increased by more than 30% since the turn of the century. I examined the traits of newly described lizard taxa, and compared them to those of species described earlier, to predict where new species will be found, what traits they have, and whether they are likely to be more extinction-prone than well-known species. I compiled data on the biogeography and ecology of newly described forms and examined the relationship between these traits and the date of description. As expected, new descriptions are generally of small species, predominantly with small geographic ranges. Most species have been described from the Oriental Realm, whereas few new species were described from Africa. New descriptions are disproportionally biased in favor of geckos and of nocturnal species – and, surprisingly, contain few subterranean forms. Newly described lizard species are more likely to be threatened with extinction and may be more susceptible to population decline. Although the rate of new lizard descriptions is still accelerating, this work contributes to predicting what types of species are likely to be found in the future – and where. The small ranges of such species, in regions suffering from severe habitat degradation, suggests that strong mitigation measures are needed to ensure that many of these species will not be lost shortly after being described.

Tail autotomy and regeneration are perhaps the most dramatic adaptations to enhance survival among lizards. In spite of much work on the subject, the ecological significance of tail autotomy rates in natural populations remains elusive, due to difficulties in controlling several confounding factors and the paucity of accurate demographic data. On the basis of a capture–recapture study, we investigate the ecological determinants of tail autotomy rates in Micrablepharus atticolus, a blue-tailed lizard from the South American Cerrado. We tested whether habitat (as a proxy of predation intensity), seasonality (as a proxy of intensity of social interactions), ontogeny and sex affected autotomy rates, and also whether autotomy rates affected body condition. We found that tail autotomy rates in M. atticolus are lower than in many other species with brightly colored tails, likely resulting from a small body size and fossorial habits. Autotomy rates were lower than expected by chance in the plot with lower mortality rates, suggesting a more prominent role of predation intensity instead of predator efficiency, and increased with age, suggesting cumulative effects of predation attempts along the ontogeny or age-specific differences in predation intensity. We also found no intersexual differences or any effect of breeding activity on autotomy rates. Our results indicate that energetic costs of tail autotomy are low, or that animals compensate tail loss with increased foraging rates. These characteristics of M. atticolus seem tightly associated with its small body size, fossorial lifestyle and very short life span, and suggest that the costs of tail regeneration should be low.

Tail autotomy is an antipredatory defense that allows lizards to escape predator attacks by shedding their tails. While the benefits of preserving life are indisputable, tail loss implies a number of physiological, social, reproductive and even metabolic costs derived from tail regeneration and reduced motility. In addition, predation risk is increased in lizards with autotomized tails. Metabolic rates increase with body temperature, which in ectotherms depends on external heat sources. Ectotherm thermoregulation is costly in terms of time consumption and exposure to predators, this cost depending on habitat thermal quality. In this work, we seek to disentangle the effects of tail autotomy on field and selected body temperature of an accurately thermoregulating lizard Psammodromus algirus in different thermal environments along a 2200-m elevational gradient. We test two non-mutually exclusive hypotheses. According to a physiological hypothesis, we expect lizards with autotomized tails to show higher body temperatures that allow them to regenerate lost tissues faster, at least when the thermal environment is not limiting (at mid and low elevations). By contrast, according to an ethological hypothesis, we expect lizards with autotomized tails to avoid exposure to predators by reducing thermoregulation time, thus showing lower temperatures than lizards with non-autotomized tails. However, we found that the tail state did not significantly affect lizard field or selected body temperatures. On the one hand, a warmer thermal optimum could imply greater exposure to predators during basking, making motility-impaired lizards with autotomized tails more vulnerable, which could explain why the physiological hypothesis of autotomy thermal effect does not apply. On the other hand, lower body temperatures could be physiologically costly for lizards, which, together with the other costs resulting from tail autotomy, could jeopardize lizard fitness. Therefore, both hypotheses were not supported.

Down-regulation of the digestive system between large meals is thought to afford energetic benefits to animals that feed infrequently. However, this idea has not been thoroughly tested. Thus, we assessed the realized benefits of infrequent feeding by examining how the timing of meal consumption influenced digestive efficiency and whole-body growth of juvenile Gila monsters, a binge-feeding lizard. All animals in our study received the same total energy intake for each feeding cycle, but meals were distributed differently over time among groups. One group had a 10–14-day period of down-regulation between meal sets while the other group had a constantly activated digestive system. The groups did not show differences in growth; however, differences in digestive efficiency for a specific meal indicate that feeding regime may have caused digestive adjustments (e.g. more efficient digestion) in one treatment group. Overall, our findings show that the energetic benefits of down-regulation may depend more on species, extent of digestive regulation, or duration of fasting than previously supposed.

Understanding how behavioural traits co-vary within and between individuals is a major aim of behavioural ecologists working across a wide range of taxa. Here we attempted to measure five key behavioural traits (aggression, boldness, exploration, activity and sociability) in a native Australian social skink, Egernia whitii . Specifically, we documented the temporal consistency of trait structural definition, the temporal consistency of trait expression and the relationships between behavioural traits (i.e. behavioural syndromes). We found (1) that the structural consistency of some traits (boldness), but not others (aggressiveness and exploration), changed across time and according to sex (i.e. the relationship between the raw behaviours that were measured in the boldness assay was different for males and females); (2) that three of the five behavioural traits exhibited moderate-to-high adjusted repeatability while two were not repeatable; (3) covariances between behavioural traits were weak to non-existent and did not support the presence of any behavioural syndromes. These results indicate that structural consistency of traits or the behavioural ‘definition’ of an aggregate score is potentially variable over time. This may limit inference on any subsequent estimates of repeatability of behavioural traits, as well as estimates of potential syndromes. Repeatability of behavioural traits may reflect underlying ecological importance, or measurement processes, and lack of behavioural syndromes may reflect lack of selection pressure for trait covariance. Studies examining multiple behavioural traits under a measurement as well as an ecological framework are crucial to make meaningful inferences regarding the ecological and evolutionary significance of behavioural traits.

Male genitalia are thought to be particularly rapidly evolving morphological structures, but there have been few quantitative interspecific comparisons between the evolutionary rates of genital and nongenital traits. We characterize the morphology of hemipenes in 25 Caribbean Anolis lizard species, and compare rates of hemipenial evolution to those of traits related to ecology or visual signaling. Using phylogenetically based comparisons of rates of evolutionary divergence, we show that genital traits evolve more rapidly than nongenital traits in anoles.

Reptile species endemic to dune ecosystems worldwide possess morphological and behavioral adaptations for burying in sand. Specializations for burying and subsurface breathing among these animals are advantageous only where sand conditions permit. The patchy distributions of many psammophilic species are presumably due to the occurrence of suitable areas where attributes of the sand facilitate locomotion, burying, subsurface breathing and nesting. The endemic, dune-dwelling Sceloporus arenicolus does not occur in areas where sand grain size composition is relatively fine, and the distribution of the species appears limited to areas with coarse-grained sand. However, the exact mechanism by which this occurs is unknown. We hypothesized that subsurface breathing is inhibited in fine sand, and tested the prediction that fine sand restricts diffusion of oxygen. We compared oxygen diffusion rates in sand with grain size compositions matching sites where S. arenicolus was present (coarse sand) to diffusion rates in samples from sites where it was absent (fine sand). We found that samples with relatively coarse sand from sites where S. arenicolus was present had higher oxygen diffusion rates than samples with finer sand where S. arenicolus was absent. These results corroborated our prediction and support the hypothesis that subsurface breathing by S. arenicolus is constrained by fine sand. This is the first step in a line of research on the role of sand grain size composition in the life history of dune-dwelling reptiles and more experiments can build on this study. Our results have broad implications for the conservation of all strictly psammophilic species by improving our understanding of the habitat elements necessary for their survival and persistence.

Patterns of body size evolution on islands provide compelling cases of rapid and dramatic phenotypic evolution in terrestrial vertebrates, yet debate remains over the relative roles of predation and resource availability in driving such evolution. We compared the morphology of five reptile species (four lizards, one snake) from Anaho Island, a desert island in Pyramid Lake, Nevada, and the nearby mainland, using museum and live-caught animals. We also examined head-shape allometries to make inferences about dietary shifts and recorded tail-regeneration frequencies (in lizards) to examine predation intensity. Compared with mainland samples, two phyrnosomatid lizard species are larger on Anaho (Callisaurus draconoides and Sceloporus occidentalis), whereas the largest (S. uniformis) is not different on the island. Conversely, the teiid lizard Aspidoscelis tigris is smaller in body and head size on the island, and the pitviper Crotalus oreganus is especially diminutive on the island, with males and females 25 and 15% smaller, respectively. Our results appear consistent with the hypothesis that body size is related to resource availability. The change in body size of the two smaller phrynosomatids may be due to interference competition. The reduction in body and head size in A. tigris suggests a dietary shift, and the dramatic difference in C. oreganus is likely due to a switch in diet from mammals to lizards. Future work is needed to determine whether body size differences reflect genetic evolution or environmental differences in growth rates or resource use. Regardless, Anaho Island, although remarkably young (early Holocene), appears to harbour a unique community of reptiles with distinct morphologies and possibly divergent life histories.

Grazing of goats on Mediterranean islets is a common practice. Its consequences on plant communities are well documented, although not on vertebrates. We aim to shed light on the effect of livestock farming on lizards by investigating five populations of the insular lizard, Podarcis gaigeae, differing in the duration and intensity of grazing. Data on grazing regime, invertebrate abundance, tick prevalence, infestation levels, gull nests and lizard densities were collected during a period of 6 consecutive years. Grazing had a negative impact on insect populations, thus decreasing food availability for lizards. Tick prevalence and infestation levels were higher in places of continuous grazing. Goat activity disturbed gulls, which avoid nesting, so depriving the islets of marine subsidies. As a consequence of all these factors, lizard densities were higher in ungrazed and lower in grazed biotopes. Grazing effects were more severe on islets communities than on the main island populations. Our data imply that management action should be taken to conserve the highly diverse islet populations.

In certain lineages of tetrapods, latitude and climate relate to body size in agreement with Bergmann’s rule. Trends for squamates are ambiguous, even between genders within a species. Therefore, additional studies are required before generalizations can be made, and attention is needed to the possibility that male and female experience distinct selective pressures and display different patterns. We examine body size in male and female Tropidurinae lizard species and test both Bergmann’s and Rensch’s rule, using phylogenetic comparative methods. We also analyze whether trends are better explained by latitude or climatic conditions. In Tropidurinae lizards, body size does not vary in accordance with Bergmann’s rule within the range of latitudes studied. Therefore, within this range, tropidurines seem not to experience thermal constraints limiting activity time, and therefore growth and body size. Yet, female body size relates to rain patterns, expectedly linked to productivity, suggesting that this gender experiences a stronger tradeoff between energy allocated to growth and to reproduction. In Tropidurinae, males tend to be larger than females and sexual dimorphism is male biased, with an isometric relationship between both sexes that does not support Rensch’s rule.

Species that occur in variable environments often exhibit morphological and behavioral traits that are specific to local habitats. Because the ability to move effectively is closely associated with structural habitat, locomotor traits may be particularly sensitive to fine-scale habitat differences. Anolis lizards provide an excellent opportunity to study the relationship between locomotion and natural perch use in the field, as laboratory studies have demonstrated that lizards that use broader perches develop longer limbs and have higher sprint speeds. We examined Anolis carolinensis (the green anole) in three habitats in close proximity. Our goals were to determine whether habitat-specific differences in hindlimb and toe morphologies occurred in a population in which perch size was variable but not manipulated, whether locomotor behaviors were associated with these morphologies, and whether habitat-specific traits differed between the sexes. We found that while juveniles in the three habitats did not differ in limb or toe morphology, adult females using broader perches had relatively longer limbs than females using narrower perches. Females also differed in toe length across habitats, but not in relation to perch diameter. Males, in contrast, exhibited differing growth patterns (allometry) in these traits, and marginal differences in locomotor behavior. Together, these results suggest that sex-specific responses in morphology and behavior, consistent with experimental observations of phenotypic plasticity, provide a mechanism for refining local habitat use.

Colour polymorphism is a widespread phenomenon among reptiles and is often associated with alternative physiological and behavioural strategies, including dispersal and movement patterns. To test the homing ability of Podarcis muralis and look for morph-specific responses, we conducted a translocation experiment in two areas of Northern Italy during 2009 and 2010. The first study area was a wall surrounding a city park with a linear and simplified habitat structure; the second one was an archaeological park in a natural area, including stone walls remains, grasses and woods. Lizards of both sexes (203 and 288 for site, respectively) were translocated at 50–200 m distances using cloth bags to block lizard sight. Podarcis muralis were able to return home as 56.7% of translocated individuals in the first site and 35.1% of translocated individuals in the second site successfully returned to their home range. The homing ability decreased with increasing distances, whereas body size positively affected homing behaviour, probably depending on the territoriality of adult lizards. More interestingly, homing performance differed among colour morphs, as yellow lizards of both sexes had significantly better homing skill than other morphs.

Ecologically induced morphological variation has been identified as a mainstay in evolutionary theory. Species that inhabit different habitats are likely to display morphological and functional differences related to the exploitation of different dietary resources available in each habitat within limits imposed by trade-offs. Here, we examine two populations of the Cape Dwarf Chameleon, Bradypodion pumilum, from fynbos (heathland) and woodland to investigate whether head morphology and bite performance are related to diet within and between populations. Stomach contents are compared with prey availability to test whether chameleons are selective with respect to prey size, hardness and evasiveness. Our data show that for adult chameleons from the fynbos (Kogelberg; n = 44), mean and maximum prey size are tightly correlated with head morphology and performance. In woodland habitat (Stellenbosch; n = 52), only maximum prey size is correlated with head morphology and performance. Fynbos chameleons showed no preference with respect to prey hardness, while those from woodland ate less hard and/or sedentary prey than available, thus preferring items that were soft and/or evasive. Finally, fynbos chameleons have a diet of sedentary and/or evasive prey similar in proportions to that available. Our results suggest that diet is not directly related to selection on the head morphology and biting performance of B. pumilum in woodland habitat, but that it may be important for selection in fynbos due to a reduction in overall prey availability.

Lizards are appropriate organisms to investigate causes and correlates of communal egg laying because their general lack of parental care focuses attention on nest site choice. We field-tested hypotheses associated with nest site choice and communal egg laying in the delicate skink Lampropholis delicata, in south-eastern Australia. Specifically, we predicted that lizards would nest at sites with lower openness and solar radiation than random sites, but within crevices with higher humidity than random crevices. However, we predicted that these environmental factors would not differ between communal and solitary nest sites (based on previous research), but that egg mortality in communal nests would be higher than that in solitary nests due to conspecific interference. Despite being ground dwellers, skinks in this population nested above the ground level in narrow horizontal crevices within vertical faces of sandstone outcrops. At the broadest scale, skinks nested at sites with significantly lower canopy openness and incident (solar) radiation than random sites, while at the smallest scale, skinks nested in crevices with significantly higher relative humidity than potential nest crevices. Humidity averaged 94% in nest sites, and nesting females did not trade-off humidity for temperature, despite an inverse relationship between the two at potential nest sites. Of 60 nests, about half to two-thirds were communal. Communal nest sites did not differ from solitary nest sites with respect to temperature, humidity, rock size, aspect, height of crevice above ground, or crevice dimensions. Eggs from communal nests were three times more likely to desiccate and perish than eggs from solitary nests, a clear cost of communal nesting. Desiccation was caused by eggs being displaced from their original positions within the crevices, possibly by conspecific gravid females.

We measured the level of fluctuating asymmetry (FA) in head shape, head scalation and femoral pores in two lizard species (Podarcis bocagei and Podarcis hispanica) from 13 islands and 15 mainland localities in the Ria de Arosa archipelago of north-western Spain. Given the recent geological history of the region, the degree of isolation to which lizard populations have been subjected can be ordered along a spatio-temporal gradient, yielding the following hypotheses to be tested: FA will be higher (1) in island populations than in mainland populations; (2) on remote islands than on islands close to the mainland; (3) on small islands than on large islands. Molecular genetic data suggest that P. hispanica is autochthonous in the Ria de Arosa, whereas P. bocagei is a more recent arrival. Therefore, we predict also (4) a higher level of FA in P. hispanica than in P. bocagei. Statistically significant results were obtained for head-shape asymmetry, supporting the second and the fourth hypotheses. With an overall meristic asymmetry index, none of the hypotheses were corroborated, whereas for certain independent meristic traits, the first, the third and the fourth hypotheses were partially supported. Both head shape and meristic traits constitute precise measures of FA, but FA is more convincingly expressed in head shape and in single meristic traits than in overall meristic traits asymmetry. We conclude that FA reflects population isolation and may be a good indicator of developmental instability. It seems worthwhile to test for FA in a landlocked system under environmental and genetic stress, for the purpose of conservation biological assessments.

In central-place territorial systems, individuals usually defend a central home site or refuge from conspecifics. Visual communication among individuals is crucial for social organization, provides information on current circumstances and allows assessment of conspecific intruders from a safe distance. We examined the role of visual cues in eliciting territorial defence behaviour in the endangered Australian pygmy bluetongue lizard Tiliqua adelaidensis. In field conditions, lizards discriminated between models of a conspecific and a similar-sized non-conspecific lizard. They displayed the highest level of aggression towards the conspecific model placed 5 cm from their burrow entrance. Male and female lizards displayed the same level of aggression and maintained an equivalent level of aggression throughout their activity season. Lizards showed less aggression towards models moved a further 10 cm from the burrow entrance. These results indicate that pygmy bluetongue lizards use visual cues in their social interactions and appear to display a central-place territorial defence social system. We interpret the distance effect as a reluctance to leave their burrow unattended because takeovers are easier if the resident is away from the burrow.

Body shape and body size are hugely important for the understanding of multiple ecological phenomena. In order to study and compare sizes across taxa and to understand the ecological significance of shape differences, there is a need for ways to ‘translate’ different size measurements to a common metric. Body mass is the most useful such common index for size across taxa. Based on a large (4900 species in 28 families) dataset of lizard and amphisbaenian weights, I generate equations to estimate weights from the common size index used in lizard morphometrics (snout–vent length). I then use a species-level phylogenetic hypothesis to examine the ecological factors that affect the variation in weight–length relationships. Legless and leg-reduced lizards are characterized by shallower allometric slopes, and thus long-bodied legless species are lighter than legged lizards of comparable length. Among legged species, the foraging strategy strongly influences the weights, with sitand-wait species being bulkier at comparable lengths than active foraging species. Environmental productivity (positively related to mass) and activity times (diurnal species being heavier) are only significant when using non-phylogenetic models. The need for effective locomotion is a major factor affecting lizard shape. Previously used allometric equations are inaccurate.

Conservation management requires knowledge of how a target species interacts with other species. Some relatively common species can modify the environment to the advantage of rarer, endangered species. Thus, local enhancement of those common species can positively influence remaining populations of the rarer species. The endangered pygmy bluetongue lizard Tiliqua adelaidensis inhabits burrows that are constructed by lycosid and mygalomorph spiders. We recorded 490 burrows in a 1 ha plot at the end of one season, and then observed at regular intervals the formation and loss of burrows, and the changes in occupancy status of each burrow over the next season. We found spiders in 94% of all newly constructed burrows and deduced that they had built the burrows. We found no evidence that lizards dug new burrows or deepened existing burrows. The numbers of both lizards and spiders in the burrows declined over the spring and summer, with lizards moving from their burrows more often early in the season than later. However, there was no strong trend for lizards to replace spiders in burrows. In fact, lizards tended to occupy deeper burrows than spiders, suggesting little negative impact of lizards on spiders. However, spiders had a positive impact on lizards by providing the refuge burrows central for lizard survival. Although lizards readily accept artificial burrows, long-term conservation for the lizards must include viable spider populations to maintain a supply of suitable burrow refuges.

Ecomorphological studies often seek to link morphology and performance to relevant ecological characteristics. Varanid lizards are unique in that species can vary in body size by almost four orders of magnitude within a single genus, and a question of considerable interest is whether similar ecomorphological relationships exist when constraints on body size are reduced. We studied sprint speed in relation to size, shape and ecology for 18 species of varanid lizards. Maximal speed scaled positively with mass 0.166 using least squares regression, and mass 0.21 using reduced major-axis regression. However, a curvilinear trend better described this relationship, suggesting an optimal mass of 2.83 kg with respect to speed. Including data for the komodo dragon Varanus komodoensis moves the optimum mass to 2.23 kg. We use this relationship to predict the sprint speed of the Komodo’s giant extinct relative Varanus (Megalania) prisca to be 2.6–3 m s 1 similar to that of extant freshwater crocodiles Crocodylus johnstoni. When differences in speed were compared to ecological characteristics, species from open habitats were significantly faster than species from semi-open or closed habitat types, and remained so after correction for size and phylogeny. Thus, despite large variation in body size, varanids appear to share similar associations between performance and ecology as seen in other lizard groups. Varanids did, however, differ in morphological relationships with sprint speed. Differences in relative speed were not related to relative hindlimb length, as is commonly reported for other lizard groups. Instead, size-free forefoot length was negatively related to speed as was the size-free thorax–abdomen length. While shorter forefeet were thought to be an adaptation to burrowing, and thus open habitats, rather than speed per se, the reduction in the thorax–abdomen length may have significant advantages to increasing speed. Biomechanical models predicting this advantage are discussed in relation to a trade-off between speed and manoeuvrability.

Sexual dimorphisms – phenotypic dissimilarities between the sexes – are common and widespread among plants and animals, and classical examples include differences in body size, colour, shape, ornamentation and behaviour. In general, sexual dimorphisms are hypothesized to evolve by way of sexual selection acting on one sex through priority-of-access for sexual partners via mate choice and/or intra-sexual competition. In snakes, males are the mate-searching sex and one form of sexual selection involves male–male competition in locating females by following pheromone trails using their forked tongues, the structure used to sample environmental chemicals for transduction in the vomeronasal chemosensory system (VNS). Based on several lines of empirical evidence, increased tongue forking (bifurcation) in snakes (and some lizard taxa) appears to enhance chemical trail-following abilities through tropotaxis (the simultaneous comparison of stimulus intensities on two sides of the body) and thus aids in prey location and mate searching in males. We predicted that male copperheads, Agkistrodon contortrix, a North American pitviper, should have more deeply forked tongues than females owing to male–male competition for priority-of-access to widely dispersed females during the mating seasons. We examined formalin-fixed, ethanol-preserved museum specimens of adult A. contortrix for sexual size dimorphism (SSD) of the tongue. Tongue dimensions showed differences indicative of SSD, and the degree of bifurcation (i.e. mean tine length) was significantly greater in males. Various structures of the VNS and associated regions (e.g. muscles) in some vertebrate taxa show sexual dimorphism, but our study is the first to document dimorphism in the tongue of a tetrapod vertebrate.