Abstract:
Invasive species are one of the top three threats to biodiversity, as well as having major impacts on primary industries, human health, recreation and cultural values. They are not easily categorised or predicted on the basis of their life-history characteristics. Biosecurity workers, therefore, need robust tools that can be used effectively to assess potential invasive species before they can do any damage. Species distribution models are one possible tool that can be used to assess the potential distribution of a species on the basis of climate matching. Hakea sericea Schrad. & J.C.Wendl. is one of many naturalised plants in New Zealand that has spread beyond its original planted locations and has invaded natural habitats. Using the model BIOCLIM in the software DIVA-GIS, I demonstrate the method of climate-matching using data from its native (Australia) and other invaded (South Africa) ranges. Comparison of these predictions is made with the known distribution of Hakea sericea in New Zealand to assess the usefulness of the model. A generalised linear model was also used with New Zealand data as a validation method. Interpretation of the results requires knowledge of the ecology and biology of the species as well as the ecological theory that underpins the model. There are many theories that could be used to explain Hakea sericea's behaviour and distribution pattern in New Zealand, and it is most likely that its success is largely due to its serotinous adaptation, which is uncommon in New Zealand plants. Differences between the predicted distribution and the actual distribution are intriguing and they highlight an area of concern for risk assessments based on climate matching for Australian species. This thesis demonstrates that species distribution models do not need to be complicated in order to be useful in visualising and assessing risk. All invasions are unique and subject to any number of variables, and any number of outcomes. While contending with such unpredictability can seem futile, species distribution modelling is a field that is constantly developing and evolving. The more we can use and refine these methods the faster it will lead to better understanding and ultimately better management of invasive species.