Modelling the Effects of Contemporary Climate Change on the Physiology and Distributions of Non-Indigenous Species

Abstract

Contemporary climate change (CCC) and non-indigenous species (NIS) are two of the biggest threats to global biodiversity and together are expected to drive a rapid global redistribution of species by the end of the century. Although understanding the interaction between NIS and CCC is crucial for the management of native ecosystems, forecasting future changes remains a significant challenge. It is thus recognised that understanding the physiological mechanisms that shape distributions and promote NIS spread is necessary to make robust forecasts under CCC. In this thesis, novel experimental and ecological niche modelling (ENM) techniques were combined to explore how the highly successful NIS, the Pacific oyster Magallana gigas, may be affected by end-of-the-century environmental conditions. The present research has shown during long-term exposure that M. gigas individuals were physiologically tolerant to CCC conditions predicted for the end of the century. It was evident that M. gigas has a broad environmental tolerance and have undergone rapid niche shifts during introduction that have likely facilitated its current rapid global spread. In addition, both correlative and mechanistic ENMs predicted that M. gigas will undergo a poleward range expansion by the end of the century. Modelling with inter-individual variability showed complex geographical changes in life-history traits in response to CCC. It was apparent that both correlative and mechanistic ENMs can complement each other and provide a unique insight into the predicted changes in species’ niches under environmental change.
This thesis presented the first long-term, multi-factor mesocosm study of M. gigas, tested the differences between popular niche shift frameworks and presented the first bioenergetic model combining inter-individual variability and environmental variability to predict species responses to CCC across large geographical areas. Taken together, a combination of techniques has produced robust predictions forecasting the continued survival and spread of M. gigas under end-of-the-century CCC.

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