Mechanisms of Invasion of Hieracium aurantiacum and Leucanthemum vulgare in Kosciuszko National Park

Invasive introduced plants constitute a significant threat to native species and ecosystems across Australia. Thorough knowledge of invasive species is thus vital to determining the threat posed, and the appropriate levels of action to be taken in their control and management. Leucanthemum vulgare (Lam.) and Hieracium aurantiacum (Nägeli & Peter) are two invasive, non-native species of Asteraceae that are a danger to the environment of Kosciuszko National Park and elsewhere. This study aimed to clarify three main aspects of the ecology of these two species: (1) their resource use efficiency and the outcomes of resource competition with native species, (2) the characteristics of the native and introduced seed bank and any impacts of invasion, (3) and the presence of allelopathy. Soil, seed and plant samples were collected from sites within Kosciuszko National Park for use in competition and allelopathy growth experiments, and in seed bank trials. Leucanthemum vulgare exhibited the best ability to utilise available resources, growing significantly larger than the other species tested under the same conditions. Competition from both invaders negatively impacted one of the native species tested, but no impacts were evident for the other species. There were no significant negative impacts of invasion on species richness, from either invader at this present time, and little evidence of homogenisation. Germinants of both invaders were significantly more abundant within invaded patches, although dispersal up to 5 m away was still evident, noteworthy for L. vulgare, which has limited dispersal adaptations. No evidence of allelopathic interference competition on native species was found. The findings reaffirm the need to continue the current eradication program of H. aurantiacum to prevent its wider establishment and to urgently reconsider the status of L. vulgare, which is not yet listed as a noxious weed in New South Wales.