Predicting performance and survival across topographically heterogeneous landscapes: the global pest insect Helicoverpa armigera (Hübner, 1808) (Lepidoptera: Noctuidae)
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Species distribution models provide a means of better understanding how climate constrains the survival of organisms. Although effective in predicting the presence or absence of species across the landscape, model outputs are not necessarily relevant to, or easily interpreted for, local management and conservation programs. An alternative approach, however, would be to use species distribution models as a tool for applied ecological projects. Integrative pest management programs, for example, which aim to control the abundance and distribution of agricultural insect pests may benefit from a model that predicts the relative performance and survival of the target pest on its host plant. We present a microclimate model to predict ambient, and thus the equilibrium body, temperature of the globally significant agricultural pest the bollworm, Helicoverpa armigera. We allow the different life-history stages of H. armigera to select specific microclimates within a host apple tree, thus developing a realistic framework for predicting core-body temperatures, and proxies for physiological performance and fitness, of this species. Subsequently, we incorporate the predicted body temperature with established data for developmental rates and critical-temperature thresholds to predict how fluctuations in temperature and variation in topography may affect phenology and survival. Although the model requires further validation against empirical data, the current outputs allow insights into how variation in local topography, farming practices and climate change will affect the relative phenology and survival of H. armigera. Moreover, the biophysical nature of the model means that with some modifications to parameter inputs, the fitness and survival of a range of pest insects on their host plants can be explored more readily.