Sceloporus Jarrovii Research Articles

Cloacal microbiomes of sympatric and allopatric Sceloporus lizards vary with environment and host relatedness.

Animals and their microbiomes exert reciprocal influence; the host's environment, physiology, and phylogeny can impact the composition of the microbiome, while the microbes present can affect host behavior, health, and fitness. While some microbiomes are highly malleable, specialized microbiomes that provide important functions can be more robust to environmental perturbations. Recent evidence suggests Sceloporus virgatus has one such specialized microbiome, which functions to protect eggs from fungal pathogens during incubation. Here, we examine the cloacal microbiome of three different Sceloporus species (spiny lizards; Family Phrynosomatidae)-Sceloporus virgatus, Sceloporus jarrovii, and Sceloporus occidentalis. We compare two species with different reproductive modes (oviparous vs. viviparous) living in sympatry: S. virgatus and S. jarrovii. We compare sister species living in similar habitats (riparian oak-pine woodlands) but different latitudes: S. virgatus and S. occidentalis. And, we compare three populations of one species (S. occidentalis) living in different habitat types: beach, low elevation forest, and the riparian woodland. We found differences in beta diversity metrics between all three comparisons, although those differences were more extreme between animals in different environments, even though those populations were more closely related. Similarly, alpha diversity varied among the S. occidentalis populations and between S. occidentalis and S. virgatus, but not between sympatric S. virgatus and S. jarrovii. Despite these differences, all three species and all three populations of S. occcidentalis had the same dominant taxon, Enterobacteriaceae. The majority of the variation between groups was in low abundance taxa and at the ASV level; these taxa are responsive to habitat differences, geographic distance, and host relatedness. Uncovering what factors influence the composition of wild microbiomes is important to understanding the ecology and evolution of the host animals, and can lead to more detailed exploration of the function of particular microbes and the community as a whole.

Sceloporus jarrovii

This datasheet on Sceloporus jarrovii covers Identity, Distribution.

The recombination landscapes of spiny lizards (genus Sceloporus).

Despite playing a critical role in evolutionary processes and outcomes, relatively little is known about rates of recombination in the vast majority of species, including squamate reptiles—the second largest order of extant vertebrates, many species of which serve as important model organisms in evolutionary and ecological studies. This paucity of data has resulted in limited resolution on questions related to the causes and consequences of rate variation between species and populations, the determinants of within-genome rate variation, as well as the general tempo of recombination rate evolution on this branch of the tree of life. In order to address these questions, it is thus necessary to begin broadening our phylogenetic sampling. We here provide the first fine-scale recombination maps for two species of spiny lizards, Sceloporus jarrovii and Sceloporus megalepidurus, which diverged at least 12 Mya. As might be expected from similarities in karyotype, population-scaled recombination landscapes are largely conserved on the broad-scale. At the same time, considerable variation exists at the fine-scale, highlighting the importance of incorporating species-specific recombination maps in future population genomic studies.

Brain transcriptomic responses of Yarrow's spiny lizard, Sceloporus jarrovii, to conspecific visual or chemical signals.

Species with multimodal communication integrate information from social cues in different modalities into behavioral responses that are mediated by changes in gene expression in the brain. Differences in patterns of gene expression between signal modalities may shed light on the neuromolecular mechanisms underlying multisensory processing. Here, we use RNA-Seq to analyze brain transcriptome responses to either chemical or visual social signals in a territorial lizard with multimodal communication. Using an intruder challenge paradigm, we exposed 18 wild-caught, adult, male Sceloporus jarrovii to either male conspecific scents (femoral gland secretions placed on a small pebble), the species-specific push-up display (a programmed robotic model), or a control (an unscented pebble). We conducted differential expression analysis with both a de novo S. jarrovii transcriptome assembly and the reference genome of a closely related species, Sceloporus undulatus. Despite some inter-individual variation, we found significant differences in gene expression in the brain across signal modalities and the control in both analyses. The most notable differences occurred between chemical and visual stimulus treatments, closely followed by visual stimulus versus the control. Altered expression profiles could explain documented aggression differences in the immediate behavioral response to conspecific signals from different sensory modalities. Shared differentially expressed genes between visually- or chemically-stimulated males are involved in neural activity and neurodevelopment and several other differentially expressed genes in stimulus-challenged males are involved in conserved signal-transduction pathways associated with the social stress response, aggression and the response to territory intruders across vertebrates.

Composition and compound proportions affect the response to complex chemical signals in a spiny lizard

Most animal signals across sensory modalities are multicomponent traits that can be broken down into discrete elements. If different elements are perceived as unique, independent units (elemental perception), instead of as integrated percepts (configural perception), single changes in the presence/absence or the abundance of specific elements of a multicomponent signal may be enough to impact communication. Here, we found that male Yarrow’s spiny lizards (Sceloporus jarrovii) can discriminate single compounds of a multicomponent chemical signal (femoral gland secretions), different concentrations of a signaling compound, and a single compound from a mixture of compounds. In addition, one chemical compound elicited a response similar to that evoked by the complete natural scent. We conclude that perception of chemical signals in S. jarrovii lizards is elemental but also configural. The elemental perception of signaling compounds seems to occur with high sensitivity and narrow resolution, so that minor changes in single key elements may affect chemical communication. Given the multicomponent nature of most animal signals, hypotheses regarding signal function and evolution would be enhanced if researchers could determine whether these results apply to signals in other sensory modalities and identify the key elements of complex signals, from a receiver’s perspective. Most signals in animal communication are quite complex. For example, odors are mixtures of multiple volatile chemical compounds, and the way in which receivers perceive and process these mixtures to extract relevant information influences the structure and evolution of chemical signals. In a series of behavioral trials, we investigated how male Sceloporus jarrovii lizards may perceive conspecific odors by testing their response to individual and combined mixtures of two compounds present in femoral gland secretions at two different concentrations. We demonstrate that lizards can discriminate structurally similar compounds and that the response to a compound changes when said compound is part of a larger mixture. Compound concentration affected the perception of individual compounds but not complex mixtures. Deciphering what elements and/or configurations are perceived in an odor mixture is the only way to understand the role of mixture composition and its impact on communication.

Changes in thermal quality of the environment along an elevational gradient affect investment in thermoregulation by Yarrow’s spiny lizards

AbstractBody temperature affects physiological processes and, consequently, is assumed to have a large impact on fitness. Lizards need to thermoregulate behaviourally to maintain their body temperature within a range that maximizes performance, but there are costs associated with thermoregulation. The thermal quality of an environment directly affects the amount of time and energy that must be invested by an individual to maintain an optimal body temperature for performance; time and energy are major costs of thermoregulation. According to Huey and Slatkin’s (Q. Rev. Biol. 1976, 363) cost–benefit model of thermoregulation, lizards should only thermoregulate when the benefits outweigh the costs. Thus, in habitats of poor thermal quality, lizards should invest less into thermoregulation. We tested the hypothesis that the thermal quality of an environment dictates investment in thermoregulation across an elevational gradient. Increases in elevation are accompanied by decreases in temperature and therefore thermal quality. We recorded body temperatures of Yarrow’s spiny lizards (Sceloporus jarrovii) at ten talus slopes along an elevational gradient of over 1000 m. We found a significant positive relationship between elevation and effectiveness of thermoregulation, opposite to the prediction of the cost–benefit model of thermoregulation. This suggests that the disadvantages of thermoconformity may be greater than the costs of thermoregulating as habitats become more thermally challenging.

Eye-Bulging Behavior in Lizards of the Genus Sceloporus: A Role in Chemical Communication?

We examined eye-bulging behavior in relation to scent-marking and chemosensory behavior in three species of iguanian lizards, Sceloporus jarrovii, S. tristichus, and S. virgatus, in a controlled en...

Partial support for food availability and thermal quality as drivers of density and area used in Yarrow’s Spiny Lizards (Sceloporus jarrovii)

Contrary to traditional models, habitat selection in ectotherms may be chiefly based on a habitat’s thermal properties rather than its food availability, due to their physiological dependence on environmental temperature. We tested two hypotheses: that microhabitat use in ectotherms is driven by food availability and that it is driven by thermoregulatory requirements. We predicted that the density of lizards would increase and the mean area used would decrease with the natural arthropod (food) availability (or thermal quality) of a plot, as well as after experimentally increasing plot arthropod availability (or thermal quality). We established two plots in each of four treatments (food-supplemented, shaded, food-supplemented and shaded, and control) on a talus slope in Arizona, USA. We measured the density and area used in Yarrow’s Spiny Lizards (Sceloporus jarrovii Cope in Yarrow, 1875) before and after manipulations, and determined whether lizard density and area used were related to natural arthropod availability or thermal quality at the surface and in retreat sites. Density and area used were unaffected by the manipulations, but both increased with natural arthropod availability and decreased with higher thermal quality in retreat sites. These results provide partial support for both food availability and thermal quality as drivers of density and microhabitat use in S. jarrovii.

The impact of ectoparasitism on thermoregulation in Yarrow’s Spiny Lizards (Sceloporus jarrovii)

Parasites are ubiquitous and can have large impacts on the fitness of their hosts. The effects of ectoparasites on physiology, behaviour, and immune function suggest that they could be part of the factors which impact thermoregulation. We tested the hypothesis that ectoparasites impact thermoregulation in Yarrow’s Spiny Lizards (Sceloporus jarrovii Cope in Yarrow, 1875) living along an elevational gradient. We predicted a positive association between ectoparasite load and body temperature (Tb), and a negative association between ectoparasite load and effectiveness of thermoregulation (de – db index). We also predicted that the impacts of ectoparasites would be greatest at high elevation where thermal quality of the environment is low because the costs of thermoregulation increase with elevation and these costs can impact thermal immune responses. We found a significant association between the number of chiggers (Trombiculoidea) harboured by lizards and Tb that depended on elevation, but no association between ectoparasite load and de – db index. The mean chigger infection rate was associated with a ΔTb of +0.18 °C at low elevation (consistent with fever) and of –1.07 °C at high elevation (consistent with hypothermia). These findings suggest that parasitism by chiggers impacts lizard Tb in a way that depends on environmental thermal quality.

Predator-prey interactions and venom composition in a high elevation lizard specialist, Crotalus pricei (Twin-spotted Rattlesnake)

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

Climate change, extinction, and Sky Island biogeography in a montane lizard.

Around the world, many species are confined to "Sky Islands," with different populations in isolated patches of montane habitat. How does this pattern arise? One scenario is that montane species were widespread in lowlands when climates were cooler, and were isolated by local extinction caused by warming conditions. This scenario implies that many montane species may be highly susceptible to anthropogenic warming. Here, we test this scenario in a montane lizard (Sceloporus jarrovii) from the Madrean Sky Islands of southeastern Arizona. We combined data from field surveys, climate, population genomics, and physiology. Overall, our results support the hypothesis that this species' current distribution is explained by local extinction caused by past climate change. However, our results for this species differ from simple expectations in several ways: (a) their absence at lower elevations is related to warm winter temperatures, not hot summer temperatures; (b) they appear to exclude a low-elevation congener from higher elevations, not the converse; (c) they are apparently absent from many climatically suitable but low mountain ranges, seemingly "pushed off the top" by climates even warmer than those today; (d) despite the potential for dispersal among ranges during recent glacial periods (~18,000years ago), populations in different ranges diverged ~4.5-0.5million years ago and remained largely distinct; and (e) body temperatures are inversely related to climatic temperatures among sites. These results may have implications for many other Sky Island systems. More broadly, we suggest that Sky Island species may be relevant for predicting responses to future warming.

Support for the thermal coadaptation hypothesis from the growth rates of Sceloporus jarrovii lizards

The thermal coadaptation hypothesis posits that ectotherms thermoregulate behaviorally to maintain body temperatures (Tb) that maximize performance, such as net energy gain. Huey's (1982) energetics model describes how food availability and Tb interact to affect net energy gain. We tested the thermal coadaptation hypothesis and Huey's energetics model with growth rates of juvenile Yarrow's spiny lizards (Sceloporus jarrovii). We compared the preferred (selected) Tb range (Tsel) of lizards in high and low energy states to their optimal temperature (To) for growth over nine weeks, and determined whether the To for growth depended on food availability. We also measured the same lizards’ resting metabolic rate at five Tbs to test the energetics model assumptions that metabolic cost increases exponentially with Tb and does not differ between energy states. The Tsel of lizards on both diets overlapped with the To for growth. The assumptions of the energetics model were verified, but the To for net energy gain did not depend on food availability. Therefore, we found support for the thermal coadaptation hypothesis. We did not find support for the energetics model, but this may have been due to low statistical power.

Ontogenetic Variation in the Thermal Biology of Yarrow's Spiny Lizard, Sceloporus jarrovii.

Climate change is rapidly altering the way current species interact with their environment to satisfy life-history demands. In areas anticipated to experience extreme warming, rising temperatures are expected to diminish population growth, due either to environmental degradation, or the inability to tolerate novel temperature regimes. Determining how at risk ectotherms, and lizards in particular, are to changes in climate traditionally emphasizes the thermal ecology and thermal sensitivity of physiology of adult members of a population. In this study, we reveal ontogenetic differences in thermal physiological and ecological traits that have been used to anticipate how ectotherms will respond to climate change. We show that the thermal biological traits of juvenile Yarrow’s Spiny Lizards (Sceloporus jarrovii) differ from the published estimates of the same traits for adult lizards. Juvenile S. jarrovii differ in their optimal performance temperature, field field-active body temperature, and critical thermal temperatures compared to adult S. jarrovii. Within juvenile S. jarrovii, males and females exhibit differences in field-active body temperature and desiccation tolerance. Given the observed age- and sex-related variation in thermal physiology, we argue that not including physiological differences in thermal biology throughout ontogeny may lead to misinterpretation of patterns of ecological or evolutionary change due to climate warming. Further characterizing the potential for ontogenetic changes in thermal biology would be useful for a more precise and accurate estimation of the role of thermal physiology in mediating population persistence in warmer environments.

Nutritional modulation of IGF-1 in relation to growth and body condition in Sceloporus lizards

Nutrition and energy balance are important regulators of growth and the growth hormone/insulin-like growth factor (GH/IGF) axis. However, our understanding of these functions does not extend uniformly to all classes of vertebrates and is mainly limited to controlled laboratory conditions. Lizards can be useful models to improve our understanding of the nutritional regulation of the GH/IGF-1 axis because many species are relatively easy to observe and manipulate both in the laboratory and in the field. In the present study, the effects of variation in food intake on growth, body condition, and hepatic IGF-1 mRNA levels were measured in (1) juveniles of Sceloporus jarrovii maintained on a full or 1/3 ration and (2) hatchlings of Sceloporus undulatus subjected to full or zero ration with or without re-feeding. These parameters plus plasma IGF-1 were measured in a third experiment using adults of S. undulatus subjected to full or zero ration with or without re-feeding. In all experiments, plasma corticosterone was measured as an anticipated indicator of nutritional stress. In S. jarrovii, growth and body condition were reduced but lizards remained in positive energy balance on 1/3 ration, and hepatic IGF-1 mRNA and plasma corticosterone were not affected in comparison to full ration. In S. undulatus, growth, body condition, hepatic IGF-1 mRNA, and plasma IGF-1 were all reduced by zero ration and restored by refeeding. Plasma corticosterone was increased in response to zero ration and restored by full ration in hatchlings but not adults of S. undulatus. These data indicate that lizards conform to the broader vertebrate model in which severe food deprivation and negative energy balance is required to attenuate systemic IGF-1 expression. However, when animals remain in positive energy balance, reduced food intake does not appear to affect systemic IGF-1. Consistent with other studies on lizards, the corticosterone response to reduced food intake is an unreliable indicator of nutritional stress. Further studies on ecologically relevant variation in food intake are required to establish the importance of nutrition as an environmental regulator of the GH/IGF axis. Within the range of positive energy balance, the potential involvement of molecular signals in growth regulation requires further investigation.

Testosterone, body size, and sexual signals predict parasite load in Yarrow’s Spiny Lizards (Sceloporusjarrovii)

Parasite load significantly impacts host health and fitness and may vary substantially among individuals within a population. The immunocompetence handicap hypothesis posits that sexual signals are honest indicators of male quality because they are maintained by testosterone, an immunosuppressant that yields higher parasite loads. Additionally, testosterone may influence parasite load by increasing activity levels. We examined these two hypotheses in a wild population of Yarrow’s Spiny Lizards (Sceloporus jarrovii Cope, 1875) in Arizona. We (i) compared fecal testosterone levels to ectoparasite and haemoparasite loads, (ii) tested if sexual signals (total coloured area, aggression, and head size), locomotor activity, and body size correlated with testosterone levels, and (iii) compared sexual signals, locomotor activity, and body size to parasite load. Ectoparasite loads increased with total coloured area and tended to increase with testosterone, but this latter relationship was only nearly significant. Parasite loads increased with body size. Thus, we found some support for the immunocompetence handicap hypothesis and none for the activity hypothesis. Our results are consistent with an alternative hypothesis that larger individuals have more parasites because they have more surface area and (or) have had longer to accumulate parasites. Future studies should examine the relative contributions of testosterone and glucocorticoids in driving variation in parasite loads.

Differences in the thermal physiology of adult Yarrow's spiny lizards (Sceloporus jarrovii) in relation to sex and body size.

Sexual size dimorphism (SSD) is often assumed to reflect the phenotypic consequences of differential selection operating on each sex. Species that exhibit SSD may also show intersexual differences in other traits, including field-active body temperatures, preferred temperatures, and locomotor performance. For these traits, differences may be correlated with differences in body size or reflect sex-specific trait optima. Male and female Yarrow's spiny lizards, Sceloporus jarrovii, in a population in southeastern Arizona exhibit a difference in body temperature that is unrelated to variation in body size. The observed sexual variation in body temperature may reflect divergence in thermal physiology between the sexes. To test this hypothesis, we measured the preferred body temperatures of male and female lizards when recently fed and fasted. We also estimated the thermal sensitivity of stamina at seven body temperatures. Variation in these traits provided an opportunity to determine whether body size or sex-specific variation unrelated to size shaped their thermal physiology. Female lizards, but not males, preferred a lower body temperature when fasted, and this pattern was unrelated to body size. Larger individuals exhibited greater stamina, but we detected no significant effect of sex on the shape or height of the thermal performance curves. The thermal preference of males and females in a thermal gradient exceeded the optimal temperature for performance in both sexes. Our findings suggest that differences in thermal physiology are both sex- and size-based and that peak performance at low body temperatures may be adaptive given the reproductive cycles of this viviparous species. We consider the implications of our findings for the persistence of S. jarrovii and other montane ectotherms in the face of climate warming.

Effects of food restriction on steroidogenesis in dispersed adrenocortical cells from Yarrow’s Spiny Lizard (Sceloporus jarrovii)

Changes in energy balance can lead to functional alterations at all levels of the hypothalamic–pituitary–adrenal (HPA) axis. However, relatively little is known about how energy balance affects functional properties of adrenocortical cells themselves. We investigated effects of restricted food intake on sensitivity to ACTH and rates of steroidogenesis in adrenocortical cells isolated from growing female and male Yarrow’s Spiny Lizards (Sceloporus jarrovii). At the end of the feeding regimen, we assayed acute (3h) progesterone (P4), corticosterone (B), and aldosterone (ALDO) production in response to ACTH in dispersed adrenocortical cells. Food restriction depressed growth rate by about 50% in both males and females but did not alter baseline plasma B measured at 10weeks in either sex. At the cellular level, food restriction had the following effects: (1) increased basal B production in both sexes and basal ALDO production in males, (2) increased net maximal rates of production of P4, B, and ALDO in response to ACTH, and (3) no overall effect on adrenocortical cellular sensitivity to ACTH. There were modest sex differences: overall rates of P4 production were 46% greater in cells from females than from males, and in response to food restriction, the net maximal rate of ALDO production was 50% greater in cells from males than from females. Our results demonstrate that food restriction in S. jarrovii increases adrenocortical cellular rates of steroid production without affecting overall cellular sensitivity to ACTH.

Diet of the Yarrow's Spiny Lizard Sceloporus jarrovii in the Central Chihuahuan Desert

We studied seasonal dietary patterns of Sceloporus jarrovii from a desert environment northwest of Gomez Palacio, Durango, Mexico. Stomach contents were examined (n = 82) and relative abundance and volume were determined. Formicids (ants) were the most abundant prey in all seasons. Other abundant foods were coleopterans (summer, winter) and isopterans (autumn, winter). Based on relative abundance in all seasons, S. jarrovii had a narrow breadth of diet, but relative volume of foods was broader. Overlap between sexes for relative abundance and volume was high throughout the year. However, low overlap in relative volume in spring indicated variation in diet between sexes. Three of the most common prey throughout the year varied significantly between sexes in length, width, and volume. However, volumes of the three most abundant foods were not correlated with snout–vent length of lizards.

Escape Decisions by the Syntopic Congeners Sceloporus jarrovii and S. virgatus: Comparative Effects of Perch Height and of Predator Approach Speed, Persistence, and Direction of Turning

Many predation risk factors operate similarly in closely related taxa, but ecological and other differences among prey species may expose them to different risks in similar circumstances. We compared escape responses by the syntopic lizards Sceloporus jarrovii and S. virgatus to similar risk factors: perch height, predator approach speed, predator persistence, and direction of predator turning. Flight initiation distance (predator–prey distance when escape begins) decreased as perch height increased in both species but was shorter in S. virgatus. Sceloporus jarrovii fled except when perch height was above 2 m., but S. virgatus often did not flee even at low perch heights. These differences may reflect lower detectability of S. virgatus, which is difficult to detect on shaded sides of tree trunks and typically escapes without climbing out of reach. Flight initiation distance was greater for the faster and second of two approaches in both species. Sceloporus jarrovii fled more frequently than S. virgatus when a nearby investigator turned away from, but not toward, a lizard. At low perch heights and when a nearby predator moves, the larger S. jarrovii is warier than S. virgatus, which may rely relatively more on crypsis than escape. Similarity of responses to some risks by both species might reflect retention of ancestral behaviors or convergence. Escape differences seem to occur when risk operates differently due to ecological differences, suggesting that aspects of escape may be molded by natural selection with at least partial independence, resulting in escape strategies suitable to the ecologies of each species.

Acomatacarus arizonensis (Acari: Leeuwenhoekiidae): New Records from Three Species of Lizards in the Mexican Chihuahuan Desert

We collected a mite, Acomatacarus arizonensis, for the first time from the states of Coahuila and Durango, Mexico. It had been reported previously only in Mexico from the Peninsula of Baja California and from Guerrero. Larvae of this mite was parasitizing the endemic lizards Sceloporus cyanostictus and Crotaphytus antiquus in the Sierra San Lorenzo, Matamoros, Coahuila, Mexico, and Sceloporus jarrovii in the Valle de las Piedras Encimadas, Dinamita, Durango, Mexico.