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. / Master of Science / Over 30 tetrapod groups have evolved a snake-like, elongate, limbless body plan. Many studies of the patterns of limb reduction (evolutionarily losing fingers and toes) have revealed a close relationship between the reduction of the limbs and body elongation; however, the loss of parts of the internal skeleton that support the limb (e.g. shoulder blade, collar bone) have been less thoroughly examined. Here computed tomography was used to generate three dimensional models of the pectoral girdle, the array of limb support bones, of the Australian lizard genus Lerista. This group contains species that have five fingers, species which are fully limbless (and thus have no fingers), and some that have intermediate numbers of fingers. I quantitatively compared the pectoral girdle shapes, which revealed that the reduction of the pectoral girdle occurs gradually and in a series of steps that are loosely associated with how many fingers are present. The pectoral girdle as a whole shows a more obvious reduction in length than in width, with this length reduction being loosely associated with the number of fingers present. Certain events appear to occur concurrently such as the loss of a small hole in one of the bones through which nerves that control the arm pass and loss of the upper arm bone. However other events, such as the loss of a cartilaginous structure called the epicoracoid is not consistently associated with any other event. The extent to which limb reduction is associated with the extent of pectoral girdle reduction is group dependent, with individuals from closely related groups showing dramatically different degrees of pectoral girdle reduction despite a similarity in the degree of digit loss. Despite these differences, the patterns in Lerista are 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 snake-like body plan, this study reveals that even in closely related groups, this transition does not proceed in exactly the same way.

The chorioallantoic membrane resides adjacent to either the inner surface of the egg shell or uterine epithelium in oviparous and viviparous reptiles, respectively. Chorionic cells face the shell or uterine epithelium and transport calcium to underlying embryonic capillaries. Calcium transport activity of the chorioallantois increases in the final stages of development coincident with rapid embryonic growth and skeletal ossification. We excised embryos from viviparous Zootoca vivipara females at a stage prior to significant calcium accumulation and incubated them ex utero with and without calcium to test the hypothesis that chorioallantois calcium transport activity depends on developmental stage and not calcium availability. We measured calcium uptake by monitoring incubation media calcium content and chorioallantois expression of calbindin-D28K, a marker for transcellular calcium transport. The pattern of calcium flux to the media differed by incubation condition. Eggs in 0 mM calcium exhibited little variation in calcium gain or loss. For eggs in 2 mM calcium, calcium flux to the media was highly variable and was directed inward during the last 3 days of the experiment such that embryos gained calcium. Calbindin-D28K expression increased under both incubation conditions but was significantly higher in embryos incubated with 2 mM calcium. We conclude that embryos respond to calcium availability, yet significant calcium accumulation is developmental stage dependent. These observations suggest the chorioallantois exhibits a degree of functional plasticity that facilitates response to metabolic or environmental fluctuations.

L'un des enjeux majeurs en écologie est de comprendre et prédire la réponse des organismes aux variations environnementales. Pour cela, la clarification des mécanismes proximaux est une étape indispensable pour comprendre des patrons écologiques généraux comme l'utilisation de l'habitat ou la distribution des espèces. Dans ce contexte, l'approche écophysiologique est particulièrement pertinente. Si la ressource trophique et les contraintes énergétiques ont attiré un intérêt considérable, les compromis liés à l'eau demeurent actuellement peu considérés. Pourtant l'eau est aussi une ressource capitale pouvant être limitante. La régulation de la balance hydrique pourrait donc jouer un rôle clé dans les compromis physiologiques et comportementaux.L'objectif principal de ce doctorat est d'évaluer l'importance des compromis liés à l'eau chez une espèce caractéristique des milieux bordiers (haies, lisières), la vipère aspic (Vipera aspis). Cette espèce vivipare est particulièrement dépendante des conditions thermiques, notamment pour sa reproduction. Notre hypothèse générale est qu'au même titre que les conditions thermiques, les conditions hydriques confrontent l'organisme à des compromis physiologiques et comportementaux importants, particulièrement lors de la reproduction (i.e., gestation). Nous avons combiné des études descriptives (thermorégulation, pertes hydriques) et expérimentales (manipulation de l’accès à l'eau) qui suggèrent l'existence d'un compromis entre la thermorégulation et la balance hydrique. Ces contraintes liées à l'eau sont associées à des ajustements physiologiques et comportementaux qui doivent être considérés pour comprendre les stratégies reproductrices et identifier de possibles conflits intergénérationnels (mère-embryons). Au même titre que les contraintes énergétiques ou thermiques, les besoins en eau sont donc essentiels à considérer pour aborder des questions écologiques et évolutives générales. / A major goal in ecology is to understand and predict species responses to environmental variations. Clarifying the proximate factors involved is a crucial step to unravel general ecological patterns such as habitat use or species distribution. In this context, the use of an ecophysiological approach can be particularly relevant. Trophic resource and energy tradeoffs attracted considerable interest but water-based tradeoffs remain relatively overlooked to date. However water is a critical, often limiting resource that must be considered. The regulation of water balance may have a key influence on physiological and behavioral tradeoffs. The main objective in this thesis is to evaluate the importance of water-based tradeoffs in a species characteristic of "ecotone" habitats (hedgerows, edges), the Aspic viper (Vipera aspis). This species is viviparous and highly depends on thermal conditions during reproduction. Our general hypothesis is that, as thermal conditions, hydric conditions should expose individuals to important physiological and behavioral tradeoffs, especially during reproduction (i.e., pregnancy).We combined descriptive (thermoregulation, water losses) and experimental studies (manipulation of water availability) that suggest a significant tradeoff between thermoregulation and water balance regulation. Water-based tradeoffs induce physiological and behavioral adjustments that are relevant to understand reproductive strategies and identify possible transgenerational (mother-embryos) conflicts. As energy or thermal resource, water should therefore also be considered to address ecological or evolutive questions.

Monitor lizards (Varanidae) are morphologically very uniform in body shape, but much diversified in body size along both phylogenetic and ontogenetic axes. A striking sexual size dimorphism exists in monitor lizards; they are capable of fast growth, metabolism and sexual maturation. I collected the data concerning body size of particular species and verified the validity of Rench's rule, which said that there is bigger difference in body size of a conspecific male and females growing with larger body size of the species. Males are markedly bigger than females. In the next step, I focused on the model species of monitor lizards, Varanus indicus. I monitored its ontogeny very carefully. I found that this monitor lizard has pronounced sexual size dimorphism, but there are only small differences in body shape. It is capable of rapid growth and sexual maturation. The sexual dimorphism in body shape is only poor, but still measurable right in those places where the selection pressures were expected. Blood sampling monitored biochemical and haematological parameters. The concentrations of the biochemical parameters revealed the economy of resources of particular sexes partially, the costs of body growth and reproduction. Although both sexes produce the same amount of biomass (the body growth of males vs. the...

Background: As the climate warms, many species of reptiles are at risk of habitat loss and ultimately extinction. Locations of suitable habitat in the past, present, and future were modeled for several lizard species using MaxEnt, incorporating climatic variables related to temperature and precipitation. In this study, we predict where there is currently suitable habitat for the genus Pogona and potential shifts in habitat suitability in the past and future. Methods: Georeferenced occurrence records were obtained from the Global Biodiversity Information Facility, climate variables (describing temperature and precipitation) were obtained from WorldClim, and a vegetation index was obtained from AVHRR satellite data. Matching climate variables were downloaded for three different past time periods (mid-Holocene, Last Glacial Maximum, and Last Interglacial) and two different future projections representative concentration pathways (RCPs 2.6 and 8.5). MaxEnt produced accuracy metrics, response curves, and probability surfaces. For each species, parameters were adjusted for the best possible output that was biologically informative. Results: Model results predicted that in the past, there was little suitable habitat for P. henrylawsoni and P. microlepidota within the areas of their current range. Past areas of suitable habitat for P. barbata were predicted to be similar to the current prediction. Pogona minor and P. nullarbor were predicted to have had a more expansive range of suitable habitat in the past, which has reduced over time. P. vitticeps was predicted to have less suitable habitat in the past when examining the region of their known occurrence; however, there was predicted growth in suitable habitat in Western Australia. Both 2070 models predict a similar distribution of habitat; however, the model produced using the 2070 RCP 8.5 climate change projection showed a larger change, both in areas of suitable habitat gain and loss. In the future, P. henrylawsoni and P. microlepidota might gain suitable habitat, while the other four species could possibly suffer habitat loss. Discussion: Based on the model results, P. henrylawsoni and P. microlepidota had minimal areas of suitable habitat during the Last Glacial Maximum, possibly due to changes in tolerance or data/model limitations, especially since genetic analyses for these species suggest a much earlier emergence. The predicted late Quaternary habitat results for all species of Pogona are conservative and should be compared to the fossil record which is not possible at the moment due to the current inability to identify fossil Pogona to the species level. P. nullarbor and P. vitticeps future models predict substantial habitat loss. P. nullarbor could potentially be considered vulnerable in the present since it already has a restricted range, and a conservation plan may need to be considered.

The purpose of this study was to evaluate putative physiological and ecological constraints on the evolution of viviparity in sceloporine lizards. In Chapters one and two, I investigated the role of in utero oxygen availability as a constraint on the capacity to support embryonic development during extended egg retention. I incubated eggs of sceloporine lizards under conditions that simulated retention in the oviduct under a range of oxygen partial pressures. In Chapter one, I tested the hypothesis that embryos of the oviparous lizard Sceloporus undulatus from a high-latitude population are laid at more advanced developmental stages and have a higher developmental rate at low partial pressure oxygen (pO2) under simulated in utero conditions than embryos from a low-latitude population. This hypothesis was rejected; embryos from the two populations did not differ in embryonic stage at oviposition or developmental rate when incubated under simulated in utero conditions at low pO2. In Chapter two I tested the hypothesis that the degree of embryonic development attained by reptilian embryos in utero is directly related to in utero pO2. The species chosen for the study differed in their capacity to support embryonic development during egg retention and were characterized by developmental arrest (Urosaurus ornatus), retarded development (Sceloporus virgatus), and normal development (Sceloporus scalaris) when eggs are retained past the normal time of oviposition. The estimated in utero pO2's for the three species increased in the order of U. ornatus (5-6 kPa) < S. virgatus (9-11 kPa) < S. scalaris (> 11 kPa). These results indicate that in utero oxygen availability is associated with interspecifc differences in the capacity to support embryonic development during extended egg retention. In Chapter three I tested the hypothesis that embryo thermal requirements determine the northern distributional limit of Sceloporus undulatus. I incubated eggs of S. undulatus under temperature treatments that simulated the thermal environment that eggs would experience if located in nests within their geographic range at 37 °N and at latitudes north of the species present geographic range at 42 and 44 °N. Incubation temperatures simulating nests at 44 °N prolonged incubation and resulted in hatchlings with shorter tails, shorter hind limb span, slower growth and lower survival than hatchlings from eggs incubated at temperatures simulating nests at 37 and 42 °N. I also predicted that the northernmost distributional limit of S. undulatus would be associated with locations that provide the minimum heat sum (degree-days) required to complete embryonic development. Eighty-four percent of location between 37-40 °N had > 495 degree-days above a threshold of 17 °C accumulated during June-September compared to eleven percent of locations between 41-50 °N. These results are consistent with the hypothesis that incubation temperature is an important factor limiting the geographic distributions of oviparous reptile species at high latitudes and high elevations. / Ph. D.

One hypothesis explaining the numerous independent evolutionary transitions from oviparity to viviparity among squamates (snakes and lizards) proposed that squamate embryonic development is independent of eggshell calcium. Recent research showed at least 25% of the calcium in hatchling oviparous squamates is extracted from the shell. Though not a direct test, these results are inconsistent with the hypothesis. To directly test the hypothesis, we removed eggshell calcium (through peeling) early in development of Pantherophis guttatus (corn snake) eggs. Survivorship to hatching did not differ between peeled and intact eggs. Yet hatchlings from peeled eggs were shorter (273.6 ± 3.4 vs. 261.0 ± 3.7 mm, p=0.0028, n=16), lighter (6.36 ±0.22 vs. 5.75 ± 0.23 g, p=0.0158, n=16), and had reduced calcium (40.8 ± 1.7 vs. 30.5 ± 1.8 mg, p