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Vertebrate genomes exhibit global methylation of cytosine residues where they occur in a cytosine-guanine dinucleotide (CpG) context and this epigenetic mark is generally thought to be repressive to transcription. Punctuating this pervasive DNA methylation landscape are short, contiguous regions of non-methylated DNA which are found at two thirds of mammalian gene promoters. These non-methylated regions exhibit CpG content close to expected levels as they escape the depletion of CpGs observed across the methylated fraction of the genome. The unique nucleotide properties of these CpG island (CGI) regions enable their identification by computational prediction in mammalian genomes. Owing to a lack of high-resolution genome-wide DNA methylation profiles in non-mammalian species, these CGI predictions have often been used as a proxy for non-methylated DNA in these organisms. In contrast to mammals, CGI predictions in cold-blooded vertebrates rarely coincide with gene promoters, leading to the belief that CGls are significantly divergent between vertebrate species, and that unique promoter-associated features may have been acquired during warmblooded vertebrate evolution. This thesis is primarily concerned with the location, establishment and biological function of non-methylated islands of DNA in vertebrate genomes. To experimentally determine genome-wide profiles of non-methylated DNA, a novel biochemical technique was established called biotinylated ZF-CxxC affinity purification (Bio-CAP), and development of this method is discussed in Chapter 3. Experimental analysis of non-methylated DNA profiles in this thesis initially addresses two main questions: (1) 'How does the non-methylated DNA landscape compare genome-wide for seven vertebrates considering distinct tissue types and developmental stages?' (2) 'How are vertebrate non-methylated regions of DNA defined and interpreted in the nuclear environment?' To address the first question, non-methylated DNA was profiled by Bio-CAP sequencing across the genomes of seven diverse vertebrate species, representing all major branch points of vertebrate evolution, and the results are discussed in Chapters 4 and S. Contrary to previously held dogma, experimentally determined nonmethylated islands of DNA (NMls) constitute an ancient epigenetic feature of vertebrate gene regulatory elements. However, despite having numerous high-resolution maps of vertebrate non-methylated DNA, the means by which NMls are identified and maintained in the nuclear environment remains poorly understood. To address the second question and identify features which determine the methylation state of DNA, exogenous DNA sequences were introduced into mouse embryonic stem (ES) c~.II~. Non-methylated DNA was profiled by Bio-CAP sequencing to investigate how different features, such as sequence-specific binding motifs, chromatin architecture and nucleotide composition of a given DNA sequence impact local DNA methylation patterns. Interestingly, the majority of exogenous promoters were appropriately non-methylated in mouse ES cells, germline and somatic cells suggesting that gene promoters have retained strong signals for the nonmethylated state across millions of years of evolution (discussed in Chapter 6). During mouse embryogenesis, genome-scale DNA demethylation and remethylation events occur to remodel the epigenetic landscape and loss of DNA methylation during this time leads to embryonic lethality. To investigate the biological function of non-methylated DNA, the third question addressed in this thesis is (3) 'What is the developmental importance of non-methylated islands of DNA during vertebrate embryogenesis?' To investigate this, members of the ZF-CxxC domain-containing family of chromatin modifiers were ablated in zebrafish embryos to perturb the chromatin landscape at NMls, and therefore interfere with their function during early development (Chapter 7). Early embryonic development and patterning was disrupted in knockdown embryos, suggesting that interpretation of non-methylated DNA and placement of chromatin modifications at NMls is essential for normal zebrafish embryogenesis. Together this work sheds light on the evolutionary origins of NMls, the mechanisms involved in the recognition and establishment of nonmethylated loci and provides an insight into the function of non-methylated DNA during early embryonic development.

Climate change is creating novel thermal environments worldwide. The alteration of thermal niches is especially challenging for ectotherms due to their reliance on body temperature for nearly all aspects of organismal performance. Characterizing the relationships between performance and temperature is therefore critical in predicting how ectotherm species and populations will persist in rapidly changing and challenging environments. To do so, scientists often characterize thermal traits with respect to aspects of physiological performance. In challenging environments, organisms will use behavioral adjustments to either enhance heating or avoid overheating. Behavior also influences many critical aspects of ecology and ultimately fitness. However, despite its ecological relevance and underlying physiological basis, behavior has largely been ignored in analyses pertaining to altered thermal niches. This dissertation explores multiple relationships between temperature and behavior in the ornate tree lizard, Urosaurus ornatus. As different species cope with novel thermal environments, elucidating the nature of these relationships will provide insight into how species may navigate altered thermal niches from both behavioral and physiological perspectives. First, I investigate the thermal sensitivity of push-up display rate, a social communication behavior utilized by U. ornatus. Display rate is influenced by an interaction between body temperature and microhabitat use, where body temperature influences display rate in different directions and magnitudes depending on the microhabitat from which the lizard displays from. Second, I quantify how thermoregulatory behavior is influenced by the presence of conspecifics. Social interactions with individuals of multiple sexes and color morphs result in individual lizards adjusting their selected body temperatures to varying degrees. Third, I assess covariation of behavioral and thermal preference traits between color morphs. Dominant male morphs are bolder, more exploratory, and prefer higher body temperatures than subordinate morphs, which helps explain habitat use variation observed between the two groups. Last, I quantify the influence of heat stress on boldness behavior. When lizards undergo a heat hardening response, a cellular mechanism that temporarily increases thermal tolerance in response to unfavorable environmental conditions, they also increase boldness expression, which could influence the adaptive potential of heat hardening as a response to heat stress. Together, this dissertation documents a suite of behavioral traits that mediate how a model species interacts with its environment. Assessing relationships between these phenotypes and temperature provides novel insight into how rising temperatures and altered thermal niches attributed to climate change may influence behavioral expression, social structure, and survival.

Throughout my thesis, I explore the importance of macro-invertebrate decomposers within Australian drylands and the influence of the loss of a terrestrial top predator on brown food webs which originate from dead vegetation. I highlight the variety of decomposition pathways in global drylands and introduce the Brown pulse framework which details the prevalence of these pathways in relation to water availability (Chapter 1). Additionally, I explore the importance of brown food webs within drylands and highlight their interactions with green food webs. The extirpation of a top predator, the dingo, from large parts of southern Australian ecosystems has allowed me to compare differences in vegetation and macro-invertebrate decomposers in their presence or absence. I showed that where dingoes were absent, there were differences in mammal communities which led to a higher density of trees and lower abundance of grass (Chapter 2 and 3). Subsequently, macro-invertebrate detritivores which feed on dead wood and dead grass were more prevalent and contributed more highly to decomposition in certain habitats over others. Where dingoes are absent and large herbivores have become overabundant, I used large herbivore exclosures to assess their influence on live vegetation cover, dead vegetation cover, detritivores, and their predators (Chapter 4 and 5). I found that large herbivores suppressed pulses of live vegetation and dead vegetation which led to lower abundances of detritivores and their predators, especially in more productive drylands. Overall, I showed that interactions within green food webs, as influenced by the presence or absence of a large terrestrial predator, disrupts the transfer of energy to brown food webs. Herbivory has also been shown to negatively influence macro-detritivores throughout global drylands (Chapter 6) suggesting that disruptions to brown food webs are experienced throughout the world. The findings from my thesis give a first insight into the interactions between green and brown food webs in drylands as well as highlighting the central role of macro-detritivores within their function. In the future, a changing climate and an increase in grazing pressure will further alter the dynamics of the green pulse and the brown pulse which will potentially disrupt the stability of dryland communities.

Presence and impacts of pathogen infections in wildlife are known to be determined by a hierarchical set of factors including host, habitat, and general environment characteristics. While an increased number of studies have been documenting host-parasite interactions in natural systems, little is known about these impacts in island ecosystems. To elucidate the impacts of infection in island populations, we investigate the effects of Hepatazoon (and apicomplexan hemoparasite) wall lizard (Podarcis erhardii) populations, on 17 Cycladic islands (Aegean Sea, Greece). Specifically, we evaluated the effects of infection on multiple aspects of lizard life history from lizards from these islands. We found significant declines of condition in infected populations, though only in male lizards, suggesting a sex-specific response to infection. Mixed model analyses also suggest that some island level characteristics can affect the health and locomotion of lizards. These results indicate variability in the impacts of malarial infection across populations of P. erhardii.

Intermittent locomotion is a commonly used escape strategy with a wide array of potential benefits. Pausing may aid in locating a predator, crypsis, lowering energy costs, and avoiding obstacles. Turning may also benefit from intermittent locomotion by allowing an animal time to assess its surroundings; therefore, decreasing the chances of making a mistake and/or stumbling. Florida scrub lizards live in environments with a variety of obstacles such as turns. The goal of this study is to quantify the locomotor behavior and performance by lizards while navigating a 45° or 90° turn. Lizards were run along both a 45° and 90° racetrack. The number of trials with pauses and pause placement was collected as well as the mean speed before, in, and after a turn. When confronted with a turn, scrub lizards will utilize intermittent locomotion over continuous locomotion. Pausing in a turn will decrease the mean speed of a turn, but the results show that the linear speed entering the turn and exiting the turn are not significantly different. This finding indicates that acceleration, not speed is crucial in escaping when presented with a turn and therefore offsets the cost of intermittent locomotion on speed.

The Florida Scrub Lizard (Sceloporus woodi) is endemic to Florida, where it inhabits fragments of xeric sandhill uplands including endangered long-leaf pine and sand pine scrub habitats. Lizards depend on a predictable range of temperatures to maximize their growth and productivity, and to do so, they shuttle among various thermal micro-environments. Thus, the spatial distribution of temperatures in the habitat is important. Habitats dominated by either high or low extremes of an organism’s preference are energetically costly and dangerous (less optimal), especially to gravid females. This study examines thermal preference of a near-threatened species that also inhabits increasingly rare habitats. I incorporate data on both sexes into a biophysical model that uses environmental and organismal data to estimate daily activity times under current and 3℃ warming climate conditions. Male S. woodi preferred a temperature 2℃ higher than that of females, whereas females had a wider thermal tolerance than males, which could facilitate adjustments to environmental change. Under a 3℃ warming scenario, females are predicted to have activity times shifted later in the day while males are predicted to experience longer activity times. These results have implications for conservationists, habitat managers, and broader considerations on the mixed effects of climate change. With variable responses to climate change, males and females are predicted to alter activity time differently in order to survive. Management decisions on the timing and types of habitat disturbance are likely to have differential effects on sexes, thus managers are encouraged to apply techniques that benefit both sexes.

Over 30 tetrapod groups have evolved a snake-like, elongate, limbless body plan. Studies of the patterns of limb reduction have revealed a close relationship between the reduction of the limbs and body elongation; however, the loss of the skeletal elements that support the limb, the pectoral girdle, has been less thoroughly examined. Here, I use computed tomography to generate three dimensional models of the pectoral girdles of an Australian skink genus, Lerista. This group contains pentadactyl species, fully limbless species and many species with intermediate morphologies. I employed a 3D geometric morphometric analysis to compare the shapes of these structures and revealed that the reduction of the pectoral girdle is correlated with the degree of loss in the limbs. The girdle in species with well developed limbs is longer and more narrow than the short, broad girdle of species with highly reduced or absent limbs, but the degree of reduction is only loosely correlated with the degree of reduction in the limbs. Certain events appear to occur concurrently such as the losses of the coracoid foramen and the humerus, but other events such as the loss of the epicoracoid are not consistently associated with any other event. The extent to which limb reduction is associated with the degree of pectoral girdle reduction and the morphology of the girdles appears to be closely associated with subclade, with individuals from closely related clades showing dramatically different degrees of girdle reduction despite similarities in the degree of limb loss. Despite these differences, the patterns in Lerista are generally more similar to each other than to those of other lizard groups, and more similar to those of other skinks than to those of other groups of lizards. Though some aspects of limb loss are common to all lizard groups that have evolved a serpentine body plan, this study shows that, even in closely related groups, this transition does not proceed in exactly the same way.

Rising temperatures across the planet are exposing populations to environmental conditions previously unexperienced by these lineages, and the responses to these changes are myriad. Depending on the species and population, responses to changing climates can encompass shifts in geographic ranges, rapid genetic adaptation, or new phenotypic distributions caused by plasticity. In the case where populations are unable to exhibit one of the aforementioned responses, extinction is the inevitable outcome. Scientists have recognized this issue and have worked tirelessly over the last 30 years to determine which species are vulnerable, how populations are responding to rapid environmental changes, and how to best conserve the most at-risk lineages. However, the efforts to predict how populations and species will persist after a century of consistent and strong climate change tend to ignore how these changes affect contemporary populations, and thus we risk missing the critical phenotypic trajectories that lead to rapid adaptation, range shifts, or extinction, which could provide both a platform for informing species conservation, but also enhance our knowledge of biodiversity. This dissertation explores how environmental variation over a variety of spatial and temporal scales impacts the selective environment in which species live, as well as the multiple plastic responses populations can exhibit in response to changing environmental conditions. First, the relationship between declining food availability and rising environmental temperatures is quantified. Food availability exacerbates organismal performance and reduces the availability of populations to mount adaptive phenotypic changes in response to changing environments. Second, the relationship between thermoregulatory behavior and individual fitness is quantified. Fitness is increased when lizards exhibit warmer preferred temperatures and can sprint faster to enhance their thermoregulatory ability. Third, the efficacy of short-term plasticity in response to heat waves is quantified. Heat waves induce “hardening responses” which are stress-induced physiological mechanisms of surviving short-term and deleterious environmental fluctuations. Indeed, when these responses are elicited, other phenotypic traits suffer which trade-off with an individual’s ability to exploit the adaptive nature of plasticity. Last, population-level variation is quantified in climate-relevant traits for populations across an elevational gradient. Breaking from other studies, I find strong local adaptation consistent with the environmental differences across populations. Together, these findings provide new insights on the co-evolution of behavior and physiology, how traits respond to environmental variability, and the efficacy of different phenotypic response options that species can use to buffer the effects of climate warming.

With rapidly warming climates, biologists are challenged to predict organismal responses to environmental variation, changes in biodiversity, and shifts in species distributions. In many cases, organismal responses differ across life stages that exhibit differences in physiological tolerances, habitat requirements, and resource allocations strategies. For instance, mobile life stages can alter behavior in response to changes in the thermal environment, whereas immobile life stages are often vulnerable to warming temperatures due to behavioral constraints and the limited microclimatic conditions experienced over small spatial extents (e.g., an embryo in an egg). Unfavorable developmental conditions can reduce growth, alter developmental rates, and increase mortality. Additionally, the developmental environment can influence subsequent life stages via changes in maturation rates, reproductive success, and survival. Therefore, organismal responses to changing environmental conditions can depend heavily on the physiology of immobile life stages as well as the behavioral and physiology capacities of mobile stages. The first empirical chapter of this thesis (Chapter Two) concerns organismal responses to warming during early ontogeny and the ecological implications of such responses for a widespread ectotherm, the Eastern fence lizard (Sceloporus undulatus). Through a series of field and laboratory experiments, I examined the effects of recurrent sublethal warming on growth, survival, and distribution of S. undulatus. I then incorporated that data into an ecological model that accounts for variation in responses to warming through ontogeny and across geography. Combining empirical studies with mechanistic species distribution modeling, we demonstrated that organisms with thermally sensitive life stages do not have to experience lethal temperatures to undergo negative changes at the individual and population levels. The second empirical chapter (Chapter Three) concerns how the capacity for adaptation to mitigate negative impacts of future climates may vary across species ranges. Using a series of field observations and laboratory-based reciprocal transplant experiment, we examined how geographic variation in maternal behavior and thermal physiology underlies patterns of growth and development across the range of the eastern S. undulatus clade. By demonstrating the extents to which genetic background and environmental conditions affect thermal biology across geography, my data serves to increase understanding of the capacities for populations to persist under climate warming.

The morphology-performance-behavior-fitness paradigm provides an integrative framework within which to examine the functional and adaptive relevance of traits at different levels of biological organization. Variation in morphological or other subordinate traits result in differences in organismal performance abilities. In turn, performance capacities constrain behavioral options, thus influencing the success of an individual during tasks that impact Darwinian fitness. These connections are frequently investigated in the context of locomotion, as locomotor abilities and behaviors are frequent determining factors in survival and/or reproductive success.Chapter One examines the relationship between endurance capacity and home range size in free-living adult male desert iguanas over two seasons. Individual endurance capacity positively predicted the home range size of adult male desert iguanas. Chapter Two describes the results of corticosterone manipulation via hormone implants with adult male desert iguanas in a laboratory setting. Neither circulating corticosterone levels nor treadmill endurance differed significantly between treatment groups.Chapter Three examines the home range of free-living desert iguanas in relation to endurance capacity, circulating corticosterone levels, and body mass, as well as ecological variables quantified for each home range. Corticosterone, endurance capacity, and home range size were not significantly related. Home range size was significantly negatively related to shade plant density. Chapter Four describes the results of corticosterone manipulation via hormone implants (modified from those used in Chapter 2) with free-living adult male desert iguanas and relationships with endurance capacity and home range size. Desert iguanas that received corticosterone implants had significantly larger home ranges, but not higher endurance, compared with those that received saline implants. Home range size was again significantly negatively related to shade plant density. No relations between corticosterone, endurance capacity, or home range size were significant.Chapter Five presents an estimate of Darwinian fitness using number of offspring sired by free-living adult male desert iguanas studied in two different years. Offspring number was calculated using DNA microsatellite analysis of paternity. In one year, home range size was a significant negative predictor of number of offspring when included in a multiple regression with corticosterone and endurance capacity. This study was limited due to small sample sizes.

Apex predators shape ecosystems through top down pressures which impact lower trophic levels through numerous interaction pathways. Lizard assemblages in arid Australia are driven by habitat structure, competition, and predation. The presence of mammalian predators in an ecosystem may influence the distribution of lizard species in Australian ecosystems. As lizards are ectotherms they are particularly sensitive to the changes in the thermal environment facilitated by climatic fluctuations, rainfall, herbivory and fire. The links between dingo control and lizard assemblages were explored using a natural experiment created by the Dingo Barrier Fence. Five years of data on predator activity and lizard assemblages from locations with a variety of management practices was used. The results showed that lizard assemblages reflected the differences in predator abundance and vegetation structure on either side of the Dingo Barrier Fence. Further investigation suggested a model where dingo control affects the abundances of lizard species via complex 4-link cascades. These findings suggest that there are winners and losers when dingoes are controlled: small lizards and geckoes benefit from dingo control while larger predatory lizards benefit from having dingoes in the ecosystem.

Numerous lizard species possess mite pockets – dermal invaginations inhabited by ectoparasitic mites, particularly chiggers (Trombiculidae, Leeuwenhoekiidae). Pockets shelter mites, and chiggers preferentially attach within pockets. However, it remains unclear how lizards benefit from this association. In the present study, associations between mites, pockets, and hosts in the Phrynosomatidae were examined using phylogenetically-independent comparative methods and ancestral state reconstructions, and hypotheses for pocket function experimentally tested using Sceloporus jarrovi (Phrynosomatidae). Mite infestations in S. jarrovi varied greatly between host demographic groups. Chiggers concentrated within the nuchal pocket in all groups, and pocket capacity was limited by host body size. Ectoparasitism significantly impaired growth in juveniles but had no effect on adult body condition. Examination of museum specimens representing 77 phrynosomatid species revealed similar patterns of ectoparasitism. Nuchal pockets occurred in 70 species; post-inguinal pockets in only 14. Chiggers consistently concentrated in the pockets despite variation in host species morphology and ecology. Comparative analysis revealed mite loads to be positively correlated with pocket size and habitat, and negatively with latitude. Pocket morphology varied considerably, displaying significant positive associations with body size and rugosity, and negative with latitude. Damage-amelioration and mate choice hypotheses for pocket function were experimentally tested using S. jarrovi. Damage-amelioration proposes pockets reduce and/or repair mite damage. Histomorphometric analyses indicate pocket tissues differ morphologically from non-pockets but do not reduce or rapidly repair damage. Instead, pockets likely reduce mite feeding efficiency and/or reduce host irritation by limiting mite damage to the superficial tissues. The mate choice hypothesis proposes pockets conceal ectoparasites from conspecifics. In mate choice trials female S. jarrovi appeared to choose males randomly; neither ectoparasite burden nor male morphology had a significant influence on female choice, and the mate choice hypothesis was not supported. Ancestral state reconstructions suggest the ancestor of Phrynosomatidae had small nuchal pockets, no post-inguinal pockets, and modest mite loads. Nuchal pockets were independently lost in Callisaurini and Uta, possibly due to specialization for arid habitats. Expansion and diversification of Sceloporus into moist, low latitude, high elevation habitats with dense mite populations coincided with enlargement of nuchal pockets, suggestive of mite-related function.

In the southeastern United States, blue-tailed skinks (Plestiodon spp.) are important hosts for Ixodes scapularis ticks, the principal vector of Lyme disease (LD) in this region. Skinks and other southeastern lizards are not thought to be reservoir competent for Borrelia burgdorferi sensu stricto (Bbss), the etiological agent of LD in the United States. . Lizard-feeding by southeastern I. scapularis may tend to suppress sylvatic cycles of B. burgdorferi, and thus may be an important reason why LD case rates in the Southeast are much lower than in the Northeast and upper Midwest. Nevertheless, some skinks in Florida and South Carolina have tested positive for Borrelia spp. bacteria. The aims of this project therefore were the following: i) to determine the natural prevalence of Bbss in Plestiodon spp. skinks from the Southeast; and ii) to determine whether or not skinks experimentally infested with Bbss-infected I. scapularis would become a source of Bbss infection for naive ticks. Forty skinks were caught in southeastern states, of which two (5%) tested positive for a Borrelia species (not Bbss). In the laboratory, 25 uninfected skinks were infested with Bbss-infected nymph I. scapularis. Bbss infection in laboratory-infected nymphs declined from 72% before feeding to 7% after feeding on these skinks, suggesting this feeding had a strong zooprophylactic effect. Only one skink subsequently transmitted Bbss to a single xenodiagnostic larva, and that infection was transient. In contrast, all infected positive control mice transmitted infection to multiple larvae for the duration of the 6-week study. Skinks in the Southeast are probably not an ecologically-significant wildlife reservoir of Bbss, and are not contributing directly to the LD cycle. The prevalence of other Borrelia species in skinks, and the possibility that such bacteria could be acquired and transmitted by human-biting ticks, remains an avenue for further study.

Life above ground requires that animals navigate a highly three-dimensional world. Both cursorial and arboreal animals must rapidly negotiate a myriad of complex and often unpredictable substrata within their habitats (e.g. dense vegetation; forest canopy) in which discontinuous supports challenge secure footholds. Traveling rapidly through such demanding terrain necessitates a behavioral repertoire that consists of both terrestrial and aerial modes of locomotion. Lizards represent an important model system in the study of general principles of how animals move. Moreover, developing capabilities of ambulation in cluttered environments to assist in search and rescue operations is in demand in robotics. Within the scope of this dissertation, I investigate whether multiple coordinated tail reflexes and responses are necessary for the successful navigation of a highly three-dimensional environment that challenges animals' locomotor systems with numerous obstacles, discontinuous supports and slippery surfaces. In Chapter One, I present data on challenging single footholds in wall-running geckos, which lead to the discovery of a control structure the significance of which had not been previously recognized. Although the remarkable climbing performance of geckos has traditionally been attributed to specialized feet, I showed that a gecko's tail functions as an emergency fifth leg to prevent falling during rapid climbing. A response initiated by slipping causes the tail tip to push against the vertical surface, thereby preventing pitch-back of the head and upper body. When confronted with insurmountable gaps the lizards exhibited tail movement as they recovered from free fall. Lizards could also control body pitch and induce turning during simulated aerial descent. These experiments suggested that the secret to the gecko's arboreal acrobatics includes an active tail.In the context of measuring locomotor performance as a function of foot-substrate interaction, I perturbed geckos even further and found that when a gecko falls with its back to the ground, a swing of its tail induces the most rapid air-righting response yet measured. Chapter Two investigates the tail as an effective torque source first attempting to generatesimple, low parameter models of thesystem, then developing thee-dimensional analytical models of multi-body systems to investigate righting performance in two species of lizard, and how it is affected by variations in tail length, mass distribution, tail placement and orientation. These results suggest that large, active tails can function as effective control appendages. Lizards gliding in a vertical wind tunnel could use appendage inertia to induce turns in yaw whereby tails twice the torso length have better yield. Robots can also serve as physical models to test our understanding of animal locomotion. In this spirit, a physical model and robot prototype tests the model's predictive capacity further, while also demonstrating feasibility of tail use in robots. In Chapter Three, I present data from field research conducted in Southeast Asian lowland tropical rainforest, the natural habitat of my model system H. platyurus. A species heretofore not known to glide exhibits considerable horizontal transit of over 4m. Geckos with tails that glided to the tree trunk were able to remain attached to it upon landing in the majority of trials, whereas geckos without tails generally became dislodged upon impact. Moreover, I present how they carry out landing on vertical tree trunks despite approaching them at very high speeds. I propose a mechanically-mediated solution to how landing on a wall could be stabilized by the caudal appendage. In Chapter Four, I explore whether representatives of lizard taxa other than Gekkonidae night utilize their tails for improving the stability, maneuverability and overall robustness of a mode of terrestrial locomotion: Rapid climbing on tree bark. Observations from the field in Malaysian lowland tropical rainforest, where I observed these animals' behavior initiated this study. I discovered that they have specialized subcaudal scales which are keeled such as to engage with a rough substrate. I present materials testing measurements using an Instron machine, where we determined that each scale can support one to several times body weight, depending on species. Acanthosaurus crucigera, Gonocephalus grandis and Iguana iguana were sampled. When the scales are prevented from engaging the animals' performance decreases dramatically.

Invasive species are considered to be the second greatest threat to native biodiversity and several factors have been identified as contributing to the success of introduced species, including their initial genetic variation and the ability of populations to adapt to a new environment. Temperature has a significant impact on reptilian ecology and distribution since they ordinarily rely on external heat sources for the maintenance of body temperatures suitable for normal activity. Body temperature affects performance in these organisms given its importance for all aspects of behavior, locomotion, courtship and rates of feeding and growth. Critical thermal tolerances can, therefore, give an indication of the range of climatic conditions that can be tolerated and which may be the causal range limit in some cases. We studied the cold tolerance (Critical Thermal Minima) of female and male invasive Anolis sagrei and native Anolis carolinensis (Sauria: Polychrotidae) in four populations along a latitudinal gradient from south Florida to northern Georgia. Cold tolerance (CTMin) was measured under field conditions and after a period of acclimation to identify whether there is variation in this characteristic as latitude increases reflecting differential selection for lower temperature adaptation or phenotypic plasticity and whether there is a difference in cold tolerance between the native and invasive species. We found a geographic cline in field CTMin for both species; the lowest CTMins were exhibited by those anoles from the northern-most population (Savannah, GA). In all four populations A. carolinensis has a lower field cold CTMin than A. sagrei, and for both species, male CTMin is lower than female CTMin. However, after a period of acclimation, there were no significant differences in CTMin among populations or between sexes of either species, suggesting a notable capacity of both species to acclimate to local conditions.

Loss of suitable habitat is a threat to species worldwide. Habitat destruction, including loss, change, and fragmentation of habitat, is the leading cause of species extinction. Eastern collared lizards (Crotaphytus collaris collaris) are habitat specialists on glades. Both C. c. collaris and glade habitats are rare and of special concern in the state of Arkansas. Many glade populations have already been extirpated in the Ozarks of Arkansas and Missouri. Increasing knowledge of the distribution, habitat structure, and population dynamics of C. c. collaris is important to ensure the survival of this species in Arkansas. A literature review of the C. c. collaris is presented in Chapter 1. Lizard characteristics, glade habitat characteristics, and information on habitat change, loss, and fragmentation of glades are described. The main goal of my thesis, presented in Chapter 2, was to determine differences across sites in environmental variables, habitat variables, tree community structure, and lizard body condition. I sought to establish differences in these factors in 17 historical C. c. collaris sites (7 with lizard presence and 8 with lizard absence) and determine if the differences were correlated with the presence or absence of C. c. collarispopulations. Significant differences in some factors were found between present sites and absent sites. Environmental variables were not related to the presence or absence of C. c. collaris, indicating a habitat phenomenon rather than environmental. Lizard presence was correlated with habitat structure, as indicated in the ground and canopy cover surveys. Present sites had a positive correlation with rock and soil cover and a negative correlation with CWD, vegetation, and canopy cover; whereas absent sites had a positive correlation with CWD, vegetation, and canopy cover and a negative correlation with rock and soil cover. Present and absent sites had a significant difference in tree community structure. Absent sites had significantly larger trees and a higher frequency of trees compared to present sites. Lizard body condition was associated with the quality and openness of the glade. These data will prove useful in conservation efforts aimed at C. c. collaris recovery in Arkansas and other glade locations in the Ozarks.

Effectively moving across variable substrates is important to all terrestrial animals. Much attention has been given to the effects of different substrates on locomotor performance in an attempt to link ecology and morphology. Sprint sensitivity is the decrease in sprint speed due to change in substrate. This study measures sprint sensitivity to substrate rugosity among six lizard species that occupy rocky, sandy, and/or semi-arboreal habitats. Lizards that use rocky habitats are less sensitive to changes in substrate rugosity, followed by arboreal lizards, and then by lizards that use sandy habitats. Phylogenetic analysis suggests that using rocks is highly correlated with decreased sprint sensitivity, long toes, and wide bodies. These results are discussed in the context of the adaptive significance of substrate selection, stability, and the evolution of sprint speed.

"Snakey Love" is a four-minute long animated graduate thesis film. The short features a female snake who pursuits her love for everyone that seems to be a snake shape, but she always fails because they are all not interested in a creature that is not their same species. However she finds her lover at in end by accident (Because there really was an accident). This short film is a 3D (three-dimensional) computer animation, which means that the final vision appears on the screen was generated by using computer 3D software. It is all done by a series of different processes like modeling, shading, rigging, lighting, rendering, etc. This paper analyzes and delineates the entire process of making this film from five different main stages. They are ideas, pre-production, production, post-production, and final conclusion and experiences.

During gravidity lizards experience a significant decrease in lung volume as a result of compression by growing eggs within the body cavity. In order to understand the effect of this decrease in lung volume on respiratory physiology of gravid egg-laying lizards I measured changes in: total lung volume, resting and post-exercise expired volume, minute volume, respiratory frequency, and carbon dioxide production during reproduction in Crotaphytus collaris and Gambelia wislizenii. I found that compression of the lungs by eggs resulted in an average 48% (range: 26 to 70%) decrease in total lung volume in C. collaris, and an average 38% (range: 29 to 46%) decrease in G. wislizenii. Despite the significant reduction in lung volume in both of these species, only breathing frequency and rate of CO2 production were significantly altered. Breathing frequency was greatest in both species when females were carrying shelled eggs, and CO2 production rate was greatest in females of C. collaris when they were carrying late-stage follicles. The significant increases in breathing frequency in both species were large enough to compensate for the decrease in lung volume and maintain relatively constant minute ventilation in both species. Crotaphytus collaris and G. wislizenii appear to be able to withstand large changes in lung volume during reproduction with little respiratory compensation.

Lizards have long served as a model system for understanding how locomotor functional morphology meets ecological demands. However, far less is known about how behavior modulates this relationship. Likewise, there is still a need for a comprehensive understanding of lizard locomotor functional morphology. This dissertation presents four studies that focus on how behavior molds locomotion and advances our understanding of lizard locomotor functional morphology.Chapter one examines variation in locomotor performance, whole-body mechanics and gaits in a phylogenetic array of lizards that use differing foraging modes. Multivariate and phylogenetic comparative analyses show that foraging mode drives the evolution of biomechanics and gaits in lizards. Sit-and-wait species used only fast speeds, trotting gaits, and running mechanics, whereas wide foraging species independently evolved slowerlocomotion, different walking gaits, and walking mechanics.Chapter two examines patterns of variation in the hierarchical relationship among morphology, kinematics and force during fast running in seven species of lizards. Multivariate analyses test for correlations among levels to reveal the morphological basis for kinematics and locomotor forces. The results show that limb length, support duration and float distance directly influence the nature of forces applied to the ground during the support phase of steady state locomotion and suggest that this relationship may affect locomotor energetics and endurance.Chapter three examines the effects of habitat, behavior, and their interaction on undisturbed locomotor speeds in Urosaurus ornatus. Detailed video analysis of undisturbed behavior reveals that locomotor speed decreases with increasing perch height, when animals move on woody substrates, and while displaying and capturing prey. No relationship is found between speed and perch diameter or substrate incline. Finally, the interaction between perch diameter and feeding behavior results in a negative relationship between speed and perch diameter during feeding but not during other behaviors. I suggest that the relationship between habitat, behavior, and speed is affected by the level of locomotor performance (maximal vs. sub maximal) that animals routinely use during undisturbedactivity.Finally, chapter four presents a detailed analysis of foraging behavior and field locomotor performance in a sit-and-wait (Sceloporus undulatus) and wide foraging (Aspidoscelis flagellicaudus) species. Both sit-and-wait and wide foraging species clump relatively slow locomotor behaviors just before prey attacks, a finding at odds with hypotheses from the literature. This result, along with previous studies, suggests thatselection on maximum speed and endurance is not acting through the filter of foraging behavior. I suggest that foraging mode should be examined in light of an existing model of animal foraging (the Webb model) to direct future studies of the ecology and evolution of animal performance in relation to foraging behavior.

Pesticides are commonly used around the world for a multitude of different purposes and on diverse habitats, including agricultural fields, wetlands, and personal lawns and gardens. Currently, acetylcholinesterase (AChE)-inhibiting pesticides are among the most prevalently used chemical pesticides in the United States. A wealth of information exists on sub-cellular responses of organisms, primarily birds, mammals, and fish, exposed to these compounds. However, the effects of AChE-inhibiting pesticides at the whole-organism level, most importantly effects relevant to an individual's fitness, have received less attention. My Master's research focused on describing the effects of carbaryl, an AChE-inhibiting pesticide, on several fitness-related traits in the western fence lizard (Sceloporus occidentalis). Reptiles are the least studied vertebrate taxon in ecotoxicological studies even though contaminants are suspected in contributing to recent population declines. Using multiple dose concentrations within the range expected to occur in nature (based on EPA application rates and published pesticide residues on insects), I quantified the effects of carbaryl on sprint performance energy acquisition, and energy allocation, traits which could have important implications for the animal's ability to avoid predators, capture prey, and grow and reproduce. I found that at the highest dose concentration, lizards experienced a decrease in arboreal and terrestrial locomotor performance, a decrease in energy acquisition, and alterations in energy allocation. My findings suggest that acute exposure to high concentrations of carbaryl can have important sublethal consequences on fitness-related traits in S. occidentalis. Future studies should examine the consequences of multiple-pulse exposures to AChE-inhibiting pesticides on reptiles.

Laboratory studies have frequently determined the maximal running speeds of lizards. However, neither the extent to which animals use maximal speeds in nature nor the effects of arboreal habitat structure on undisturbed locomotion have been well documented. Thus, I quantified available habitat, perch use, and the undisturbed locomotor behavior of four Anolis lizard species (A. sagrei, A. carolinensis, A. angusticeps, and A. distichus). Narrow, short, and steep perches dominated the study site. The selection of all perch attributes (diameter, length, and incline) was biased for A. distichus, whereas each of the remaining species randomly used at least one perch attribute. Narrow breadth of resource use most often reflected the narrow breadth of available resources rather than selective use of resources. The undisturbed speeds and movement distances of all species were exceedingly slow and short, suggesting that neither maximal sprinting speeds nor endurance capacities were taxed frequently in the field. Furthermore, the effects of habitat structure on undisturbed locomotor speeds and movement distances were highly species-specific. The escape responses of animals frequently involve choosing between alternative paths. Because many attributes of habitat structure can influence locomotor performance, path choice may affect the ability of an animal to evade predators. In arboreal habitats, discontinuous networks of perches create discrete paths, and many perch attributes have predictable consequences for arboreal locomotion. Thus, to determine whether paths are randomly chosen and to assess trade-offs between the speed and maneuverability of arboreal locomotion, I quantified path choice and the escape locomotor behavior of the four Anolis species. I chased lizards across the branching points of perches in the field and on standardized artificial perches in the laboratory. Despite interspecific differences in microhabitat preferences, most individuals of all species chose perches with the largest available diameter and the straightest interperch angle in the field trials. In laboratory trials, most individuals traveled on a 4.8-cm diameter perch with a 45°( turning angle rather than choosing a straight path with a 1.0-cm diameter. Both field and laboratory data suggest that Anolis species usually choose escape paths to optimize the speed of escape locomotion.

Arboreal animals often move in habitats with dense vegetation, narrow perches and variable inclines, but effects of arboreal habitat structure on locomotor function are poorly understood for most animals. Several species of Anolis lizards, which have served as a model group for relating locomotor performance to morphology, have decreased maximal sprinting speeds when perch diameter decreases. However, the effects of perch diameter on the limb movements of Anolis have not been previously studied. Hence, I quantified the hind limb movements of Anolis sagrei, which naturally occurs on a wide variety of perch diameters and inclines. For each lizard, I obtained similar speeds of steady locomotion for each combination of round perches with diameters of 1, 3, 6 and 10 cm and uphill inclines of 0°, 45° and 90°, as well as a flat surface inclined at 0° and 45°. The effects of diameter and incline were widespread as 54 of 60 kinematic variables changed significantly with either diameter or incline. Diameter significantly affected nearly twice as many kinematic variables as incline (44 versus 24), but many kinematic variables were changed little with increases in surface diameter beyond 6 cm. A. sagrei used a more upright limb posture on narrow perches and had a progressively more sprawled limb posture as surface diameter increased. Stride length, step length and stride duration increased significantly with increased perch diameter. Significantly greater knee flexion during stance was important for locating the foot more medially during movement on narrow perches. Femur depression, femur retraction and long-axis femur rotation decreased significantly as the surface diameter increased. The foot is most lateral to the hip during the swing phase and maximal lateral displacements decreased with decreased perch diameter. Consequently, the width required to accommodate limb movement also decreased as perch diameter decreased.

Arboreal animals, especially lizards, often traverse three-dimensional networks of narrow perches with variable inclines, but the effects of both incline and narrow surfaces on the locomotor movement and function of limbs are poorly understood. Thus, I first quantified the three-dimensional hindlimb kinematics of a specialized arboreal lizard, Chamaeleo calyptratus, moving horizontally, and up and down a 30° incline on a narrow (2.4cm) perch and a flat surface. I compared the flat-surface data of C. calyptratus with those of an anatomically generalized terrestrial lizard, Dipsosaurus dorsalis. Second, I studied the hindlimb muscle activity of C. calyptratus on inclines of -45°, 0°, and 45°. I quantified electromyograms (EMGs) from nine hindlimb muscles, and correlated EMGs with three-dimensional hindlimb kinematics. Inclines had significant main effects for relatively few kinematic variables of C. calyptratus (11%) compared to D. dorsalis (73%). For kinematics of C. calyptratus, the main effects of the flat surface versus round perch were nearly three times more widespread than those of incline. The foot of C. calyptratus was markedly anterior to the hip at footfall, primarily as a result of an unusually extended knee for a lizard. A large amount of knee flexion during early stance may be used by C. calyptratus to actively pull the body forward in a manner not found in most other lizards and vertebrates. Despite the kinematics changing little with incline, the EMGs changed substantially. Most of the changes in EMGs were for amplitude rather than timing, and the hip and thigh muscle EMGs had more conspicuous changes with incline than those of the lower limb muscles. The knee flexion of C. calyptratus during the first half of stance was correlated with two large knee flexors which both increased in amplitude when moving uphill compared to level and downhill. Thus, early stance probably contributes significantly to propulsion in C. calyptratus. During stance, the EMGs of the caudofemoralis muscle in C. calyptratus correlated well with femur retraction, knee flexion, and posterior femur rotation, which provide propulsive forces. Many of the muscles in the hindlimb of C. calyptratus changed activity with incline in a manner similar to the propulsive limb muscles in mammals.

Mate competition is a prominent component of sexual selection theory. Typically, males attempt to mate with the most females possible and females attempt to mate with the highest quality males possible. In the polygynous female-defense mating system of Anolis carolinensis, males compete directly for females through territorial behavior. Inter-male competition is intense due to an average polygyny ratio of 1 male to 3 females despite a 1:1 adult sex ratio. Through high levels of territorial behavior (e.g., 100 displays/h, 27 m patrol distances/h, 70% of day in defense-related activities), males attempt to exclude other males from resident females who, in turn, both store sperm and ovulate a single-egg clutch at weekly intervals over a 4-month breeding season. Paternity of hatchlings in 16 naturally occurring breeding groups was analyzed to determine the extent to which the territorial resident male was able to prevent other males from fathering offspring of his resident females. Lizards residing in or neighboring a resident male's territory were collected and RAPD-PCR was used to determine the paternity of hatchlings. Of the 48 hatchlings from 26 females, resident territorial males fathered 52% of hatchlings; 15% were fathered by a male whose territory bordered that of the resident male and 21% were fathered by a smaller male living covertly within the resident male's territory. Paternity for the remaining 12% of hatchlings belonged to an unsampled male. Given that females mated with multiple males, laboratory-based controlled matings were conducted where females were sequentially paired with two males and RAPD-PCR was used to analyze which of the two males fathered the subsequent hatchlings to determine the mechanism of sperm precedence. Regardless of mating order, only one male of the pair fertilized the eggs. Male A. carolinensis have reproductive strategies present in addition to defending resident females and female A. carolinensis have options in addition to simply mating with the resident male. While sperm precedence is present in this species, it is not based on mating order, but may involve both the number of sperm deposited in the female's tract as well as the quality of those sperm.

Adult green anoles, Anolis carolinensis, exhibit numerous sex differences resulting from divergent strategies for maximizing reproductive success. I focused on the ontogeny of sex differences in behavior in juveniles, in relation to adult sex differences, by documenting the behavior of free-ranging juveniles, examining the structure and use of headbobbing displays, and determining the role of the androgen testosterone (T) in producing behavioral sex differences. Field observations indicated that juvenile males eat and forage actively more often than juvenile females. This divergent feeding behavior may result from sexual selection, given that body size is a major factor in determining the reproductive success of males. Analyses of headbobbing displays, used by adults in aggressive and sexual interactions, revealed that juvenile males and females each give the same three A, B, and C display types described for adults. However, there may be a maturational component to display structure, as juvenile displays differ from those of adults in within-display temporal structure, and are not as stereotyped. Concerning display use, social context affects neither the types of display interactions observed nor the rates of displays and related behaviors. However, size affects nearly every aspect of display behavior. Both juvenile males and females show increased display rates and probabilities of expressing display-related behaviors with increasing body size, although in the largest juveniles, male display rates become higher than those of females. These results, like those from analyses of display structure, suggest a maturational component to display use, perhaps mediated by changes in the underlying motivational states of juveniles. Consistent with the divergence in display rates in large juveniles, males of approximately 30 d of age and older have higher plasma T concentrations than females. Furthermore, juvenile males and females that have been given T implants each respond with increased behavior levels, approaching those of breeding adult males. These analyses indicate that sexual dimorphisms in behavior in adults likely arise through underlying physiological differences between males and females that mediate the expression of behavior, rather than through fundamental sex differences in the ability to perform these behaviors.

I evaluated possible constraints on the evolution of viviparity in the lizard genus Sceloporus by experimentally extending the length of egg retention past the normal time of oviposition for a number of oviparous species. Observations also included a representative of the genus Urosaurus, the sister genus to Sceloporus. I determined the effects of retention on embryonic development, hatchlings, and gravid females. Results indicated that the proximate constraints on longer retention times and viviparity are 1) embryonic development becomes arrested or severely retarded in utero, and 2) the ability to maintain gravidity past the normal time of oviposition is limited in some species. Observations on Urosaurus further showed that extended egg retention results in hatchlings with traits that are associated with lower fitness. I also tested the hypothesis that reproductive Sceloporus lower their body temperatures during activity because their normal body temperatures are detrimental to embryos. Observations on a viviparous species of Sceloporus indicated that the normal body temperature of the female was detrimental to embryonic development. This result is indicates that viviparity would be constrained in some squamate lineages if maternal body temperatures are too high for successful embryonic development. I also evaluated the hypothesis that the evolutionary transition from oviparity to viviparity involves a "reduction" of the eggshell concurrent with longer durations of egg retention. If this hypothesis is correct, then attributes of eggshells that should enhance exchange of respiratory gases (i.e., thickness, density, permeability to water vapor) would be correlated with the maximal developmental stage that embryos are able to attain in the oviducts (i.e., stage of developmental arrest). The results of this study indicated that these features of shells do not determine the stage at which development becomes arrested. Thus, the results do not support the hypothesis that shell reduction occurs concurrently with longer periods of egg retention. The results are consistent with the alternative hypothesis that reduction of the eggshell occurs after viviparity has evolved.