Species occupancy, distribution and abundance: indigenous and alien invasive vascular plants on sub- Antarctic Marion Island

The main objectives of this research are to examine and test predictions relating to the relationship between occupancy, abundance, aggregation, and scale on Marion Island. Additionally, the impact of terrestrial invasive species on indigenous plant species is investigated, and particularly how they interact with the indigenous plants and each other. The thesis is split into five chapters, with the first chapter being a general introduction to topics of species abundance and distribution patterns as well as alien species in the sub-Antarctic. In chapter two, the generality of the abundant centre hypothesis (Brown 1984) is tested by examining the geographic abundance structure of Azorella selago at an island-wide scale. In the third chapter, the impact of alien house mice on A. selago as well as the spatial variation in structural damage to A. selago by mice is investigated at a landscape scale. The fourth chapter focuses on the distribution and spatial patterns of two alien vascular plant species, Agrostis stolonifera and Sagina procumbens, and the indigenous Acaena magellanica and how they interact with each other along rivers. In the fifth and final chapter, the general findings for each chapter (chapters 2-4) are summarised and synthesised, and the possible implications and influences of the alien species on macroecological patterns of Marion Island's indigenous biota are discussed.