What does climate change mean for the ecology, invasiveness and management of tephritid pests in Australia?

Tephritid fruit flies are among the most devastating pests to Australia's multi-billion-dollar horticulture industry. The Australian National Fruit Fly Strategy (2010) identified 46 native and exotic species as 'high priority pests' of concern, the management of which are vital for plant protection and biosecurity. While considerable research attention has been given to several of these species, to date the potential for climate change to alter the distribution and relative risks of these species has been largely overlooked. My thesis aims to bridge this gap. In addition to the introduction and conclusion, my thesis consists of three data chapters and a review chapter. The thesis is structured as a series of papers, one of which has been published and with another accepted. Chapters two and three utilised the species distribution model Maxent to map suitable habitat for Tephritidae pests under current and future climate scenarios for 2030, 2050 and 2070. Maxent is a correlative SDM that has been widely used to assess the distribution of suitable habitat for a broad range of pest and invasive species. Chapter two focused on the most economically costly of the Tephritidae pests in Australia- the Queensland fruit fly, Bactrocera tryoni (Froggatt) (Qfly), which attacks more than 100 native and introduced host plant species. My model indicates that south-western Western Australia, northern regions of the Northern Territory, eastern Queensland, and much of south-eastern Australia, southern Victoria and eastern Tasmania are currently suitable for Qfly. It also indicates that most areas that are currently suitable will remain so throughout much of this century. My results provide guidance on the potential exposure of Australia's horticultural industry to Qfly as climate changes. In Chapter three, I extended my modelling approach to the 11 native, high priority, economically important tephritid pests that are present within Australia. In this chapter I identified 'hotspots' (regions suitable to multiple pest species), to guide Australia's horticulture industries in developing effective monitoring and management strategies. My results highlight that the Wet Tropics is likely to be vulnerable to all 11 species until at least 2070. As the century progresses, the east coast of Australia, Cape York Peninsula and Northern Territory are likely to remain vulnerable to multiple species, however, extrapolation to novel climates in these areas decreases confidence in model projections. My results also indicate that the vulnerability of major horticulture areas in eastern Queensland, southern-central regions of New South Wales and southern Victoria to these pests may increase. Chapter four represents a risk assessment of 19 non-native invasive species that are currently not present in Australia but that have been identified as having the potential to pose considerable risks if they establish. I assessed their relative establishment likelihood under current and future climates by combining maps of a) regions of Australia with a climate similar to species' known ranges, b) a key arrival pathway (i.e. the movement of people entering Australia from host countries) and c) the distribution of horticultural lands. I found that Bactrocera dorsalis has the highest establishment likelihood under all climate scenarios, followed by Zeugodacus cucurbitae and B. latifrons. Chapter five presents a literature review of the potential impacts of climate change on tephritid fruit flies, particularly those in Australia. In doing so, I outline likely responses, key knowledge gaps, and implications for horticultural industries. My thesis provides the horticultural industry in Australia with a greater understanding of the relationship between fruit fly pests and climate change, and highlights the importance oflong-term vigilance to ensure the long-term security of this industry.