Zoology - Theses

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    Predicting responses to climate change: ecophysiology of the common brown butterfly, Heternoympha merope
    Barton, Madeleine Grace ( 2013)
    Understanding the processes through which climate limits the distribution and abundance of organisms is a fundamental question in ecology, and is particularly important in light of recent, on-going, climate change. Variation in temperature in particular, can have substantial impacts on the fitness and survival of organisms, through its ubiquitous effects on biological rates. However, animals have the capacity to construct their own thermal environment through behaviour, and so to understand the impacts of temperature on species’ ecology, interactions between the organism and its environment must be accounted for. Holometabolous insects make fascinating systems with which to explore the impacts of temperature on fitness, because the different life-cycle stages vary in thermal sensitivity, their capacity to behave, and in the environments encountered. Furthermore, the different life-history stages are invariably linked: conditions experienced by one life-cycle stage have a direct impact on the fitness and survival of subsequent stages and generations. Consequently, understanding how climate constrains the survival of such species requires a holistic approach, in which all stages of the life-cycle are considered. This thesis focuses on an endemic, widespread Australian butterfly, the common brown, Heteronympha merope. To ascertain how the life-cycle phases of H. merope differ in their thermal sensitivities, I measured the impact of temperature on a suite of fitness traits including development time, growth rate, body size, flight, longevity, starvation and fecundity. As adult butterflies have a broad scope for behavioural thermoregulation, I also quantified how basking posture affects the core-body temperature of H. merope. These empirical datasets were subsequently incorporated into a mechanistic model, which was run across the Australian landscape with high-resolution, spatial climatic datasets to identify processes that constrain H. merope’s distribution. These models incorporate variation in thermal sensitivities, behaviour and dispersal potential of the different life-history phases to attain a comprehensive understanding of how climate limits the common brown’s survival. The final model provides a powerful tool for holistically assessing how organisms with complex life cycles, such as butterflies, are likely to respond to future climate change.