Assessment and prioritisation of plant species at risk from myrtle rust (Austropuccinia psidii) under current and future climates in Australia

Myrtle rust (Austropuccinia psidii) is an invasive rust fungus that attacks species of the Myrtaceae family, one of the most dominant plant families in Australia. The potential extent of myrtle rust affected areas and the high number of potential host species make a species prioritisation scheme essential to direct conservation and management efforts. This study builds on previous work by: compiling an up-to-date list of myrtle rust occurrences and host species; mapping current and future climate suitability for myrtle rust; and identifying host species at risk based on range overlaps and susceptibility data. Suitable habitat for myrtle rust is restricted to eastern and southern coastal areas of Australia, with minor areas in the Northern Territory and Western Australia. This coastal distribution remains present under future climates, with some extension in inland New South Wales and Tasmania, and a reduction of suitable habitat in northern Queensland and Western Australia. Contrary to previous studies, our results indicate that south-west Western Australia has low climatic suitability for myrtle rust. Under current climate, 1285 Myrtaceae species are at risk of exposure to myrtle rust. This number decreases to 1224 species under future climate. We divide species exposed to myrtle rust into three priority categories, giving highest priority to species with at least 70% of their range overlapping regions climatically suitable for myrtle rust under current or future climates. We find 23 species are of high priority for conservation action. Finally, we provide a series of recommendations for management of species within each priority category.