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Bipedalism is commonly assumed to be an adaptive convergence because it has evolved independently three times in small desert rodents. However, the functional benefits of bipedality in this ecosystem have long been unclear. In this thesis I integrate phylogenetics, functional morphology, biomechanics, information theory, and behavior to investigate whether and how bipedality increases fitness in desert ecosystems, and whether bipedal rodents convergently evolved to have the role in their respective ecosystems. Based on the diversity of extant dipodid rodents, I begin by statistically reconstructing the pattern of morphological evolution in jerboas. I find that the strongest indicator of bipedality is metatarsal to humerus length, and that changes in this ratio are associated with increased rates of speciation, supporting a punctuated equilibrium pattern of evolution in this clade. Furthermore, the distinct patterns of morphological evolution suggest that a complex suite of genetic and developmental mechanisms governs the acquisition of bipedality in jerboas. I then use an inverse dynamics approach to characterize the biomechanics of bipedal hopping in a derived jerboa. I find that the dynamics of jerboa hopping are generated predominantly by muscular contractions, rather than tendon--based elastic energy storage and return between strides. Therefore hopping in small rodents favors rapid production and absorption of forces, rather than sustained bouts of steady--state locomotion. By reviewing predator--prey studies in biomechanics, ecology, and evolution I hypothesize that ricochetal locomotion enhances the ability of small rodents to evade predators that hunt via ballistic interception. I then develop Information Theoretic techniques to measure the unpredictability of escape trajectories in sympatric bipedal and quadrupedal rodents. As expected, bipedal rodents use significantly more unpredictable escape trajectories, likely enhancing predator evasion ability and enabling foraging in exposed areas with higher predation risk. I then found that bipedal rodents exhibit a stronger preference for exploring open spaces, matching previously established foraging patterns. These findings suggest that the evolution of bipedality enables spatial resource partitioning to limit interspecific competition in desert rodents. Based on the functional studies in my thesis, I evaluate ecological models to predict the occurrence of convergent bipedal rodents in Myomorpha. I show that diet specialization and aridity are insufficient to predict the locomotor morphology of these rodents and develop novel hypotheses for the convergent evolution of bipedalism in desert rodents. My thesis investigates the functional consequences of morphological evolution in the context of evolutionary ecology. By considering the interconnectedness of ecology, behavior, and evolution, studies in biomechanics can be designed to inform each of these fields. This interdisciplinary approach is necessary to study the adaptive nature of behavioral traits that are governed by myriad genetic, developmental, and environmental factors., Biology, Organismic and Evolutionary

Temperature plays an important role in shaping the form and function of every species. Ectothermic organisms are particularly sensitive to fluctuations in their thermal environment. Their inability to produce appreciable amounts of heat through physiological mechanisms makes them particularly vulnerable to thermal shifts, and ideal for the study of temperature-mediated evolution. The central goal of this dissertation is to understand how temperature shapes the evolutionary history of terrestrial ectotherms during the colonization of novel environments. Towards this aim, I focus on a single species of lizard, the North American green anole, Anolis carolinensis. In the first chapter of my dissertation I trace the phylogeographic history of A. carolinensis in order to identify the geographic distribution of major genetic lineages within the species and its Cuban relatives, date times of divergence between these lineages, and identify geographic barriers to dispersal. In the second chapter, I use an integrated approach to identify aspects of the environment that may have influenced evolutionary adaptation within the species. I combine geo-referenced climate data, environmental niche modeling, thermal physiology, common garden experiments and genomic techniques to understand phenotypic and genomic response of this historically subtropical Cuban lizard to the more temperate regions of the American Southeast. Finally, in the third chapter I use experimental temperature manipulations and physiological testing to explore the roles of phenotypic plasticity and local adaptation in shaping latitudinal variation in thermal tolerance and identify potential systemic mechanisms involved. As a result, I have identified a Miocene origin of the initial over-water dispersal event leading to the establishment of the green anole in peninsular Florida, followed by a rapid Pleistocene range expansion of the species northward into higher latitudes. Range expansion on the mainland has led to thermal niche expansion, mediated by a combination of local adaptation of cold tolerance and genetic isolation by environment between populations from different thermal habitats. Phenotypic plasticity and canalized differentiation both shape variation in cold tolerance across latitude and energy conservation via metabolic suppression under acute and chronic cold onset may help to extend the limits of cold tolerance in this species at its northernmost latitudes., Biology, Organismic and Evolutionary