Invasive plants and pathogens in Australia

Abstract

Exotic plants and pathogens introduced to Australia have had significant impacts on species, vegetation communities and on ecological processes. There are approximately 2700 exotic plant species that have become naturalised within Australia and of those, around 250 are considered problematic. The sources of introduction have shifted from Europe, Australasia and North America to South America more recently, with the vast majority of introductions associated with the horticultural industry. The proportion of exotic species within the flora increases from northern Australia to the southern areas of the continent, with successful invasion related to high human density and associated disturbance, particularly increased nutrients and high grazing pressure. This chapter describes the main functional types of plant invaders and their impacts across the major regions of Australia. Invasion by exotic woody invaders, plants, perennial grasses, annual herbs and grasses, vines and aquatic plants have caused substantial changes in vegetation structure and composition, with reduced native species diversity and changes in ecosystem processes, such as hydrological and fire regimes. This chapter also describes the impact of two important plant pathogens that have been introduced to Australia – phytophthora (Phytophthora cinnamomic) and myrtle rust (Puccinia psidii). These pathogens have both resulted in declines in abundance of some susceptible plant species and resultant changes in vegetation composition. Finally, we discuss current weed management approaches in Australia and future research directions