Aspects of the ecology of Astelia australiana, Tall Astelia

The conservation of threatened species requires an understanding of their ecology to identify the factors that are contributing to their decline and to assess their extinction risk. The objective of this thesis was to examine the ecology of Astelia australiana, a threatened herb endemic to Victoria, Australia to inform its conservation management. To achieve this objective, I examined how the distribution and abundance of A. australiana has changed over its entire known range in the 20- year period since its demographic monitoring program began. I also examined its habitat niche and regeneration ecology and response to potential threats including drought, wildfire, disease and low light availability. I then used this new understanding to develop a population viability model to explore the viability of A. australiana to current conditions, threats and limitations. The key findings of my research include a better understanding of the regeneration ecology of A. australiana including that it involves both sexual and asexual reproduction which occur at the same time. This reproduction occurs once in an individual’s lifetime and results in the production of flowers and fruit and three clones. Previously A. australiana had been variously described as dioecious and gynodioecious; however, it is trioecious, having male, female and hermaphrodite flowers on different plants and male and hermaphrodite flowers on the same plants. Various native bird and mammal species are involved in the regeneration ecology of A. australiana as pollinators and dispersers of fruit. Reproduction of A. australiana requires a minimum amount of available light from canopy gaps in the rainforest understorey to occur. A. australiana has declined in abundance by 57% over the 20-year period. Herbivory, and disease have contributed to mortality of A. australiana over this period but do not appear to be the only factors contributing to the observed decline. Although, A. australiana was found to be highly