Abstract/Summary

Invasive plant species represent a serious threat to biodiversity, precipitating a sustained global effort to eradicate or at least control the spread of this phenomenon. Current distribution ranges of many invasive species are likely to be modified by climate and land use change. This thesis presents a series of papers that aims at mapping the current distribution and predicting the potential future distribution of Rhododendron ponticum L. (family: Ericaceae). The series of papers aims to determine, a) the most important abiotic (environmental) factors affecting the distribution of R. ponticum in the UK, focussing on Wales as a case study, b) whether the niche of this species has shifted or remained conserved in the UK (compared to its native range), c) the selection of optimum modelling parameters for correlative species distribution model, d) future land use and land cover change maps for the study area and finally, e) assessing the combined effects of land use and climate change on potential future distribution of R. ponticum in the UK. The main results suggest that land cover and topography are critical in limiting the distribution of this invasive plant. Furthermore, ecological niche of R. ponticum has shifted in the UK compared to the Iberian Peninsula (native range), arguably due to hybridization. Model performance in the training areas improve with decreasing grain size of predictors (50 m > 300m > 1 km). However, model transferability requires optimum grain size which should be determined by testing a range of grain sizes. In most of the future land use and climate change scenarios, invasiveness of R. ponticum is likely to decrease by as much as 40 % of the currently invaded area. The results highlight the importance of considering a range of land use and climate change scenarios and including regional policy-based land use change projections to test the potential of invasive species to expand or retreat in future. Eastern belt and south western parts of Wales are vulnerable to future invasion of R. ponticum because of possible increase in temperature and forest cover under future scenarios. Invasion risk maps produced in this study could guide pre-emptive management strategies.