DISSERTATION RESEARCH: Comparative thermal physiology and evolution of Australo-papuan Eugongylus skinks: testing Janzen's hypothesis for gradients in species diversity

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An understanding of temperature physiology is necessary to comprehend many biological phenomena, such as temporal and spatial patterns of growth, species diversity, and range size. Comparative studies of thermal physiology also yield insight into how intrinsic physiological limits affect the propensity for speciation and explain macroevolutionary patterns, such as the latitudinal diversity gradient. The proposed research will examine temperature responses and traits for a set of related forest lizards across an extensive latitudinal gradient (tropical New Guinea to temperate Tasmania) and between montane and lowland taxa, all in a phylogenetic context. Central predictions are that thermal tolerance breadths will be narrower in species at lower than high latitudes and wider for species at high compared to low altitudes. Measurements of thermal tolerance and other physiological parameters will be considered in relation to phylogeographic data to test the hypothesis that tropical taxa are more prone to topographic isolation and hence speciation due to physiological limits. This project seeks to explicate mechanisms responsible for a major macroevolutionary pattern, the latitudinal diversity gradient, but it also has implications for conservation. To minimize biodiversity loss, ecosystems must be managed by prioritizing conservation areas based on vulnerability, which requires that factors governing sensitivity to environmental change be identified. Sensitivity is controlled by intrinsic traits of a species, such as physiological limits. Mechanistic species distribution models that integrate physiological traits may provide greater predictive power when extrapolating to novel situations likely to cause range shifts or extinctions. Thermal physiological traits of species estimated through this research will be incorporated into such models to assess which species might be most vulnerable with impending climate change and thus identify conservation priorities.