Abstract:
Moth plant (Araujia hortorum E.Fourn. Apocynaceae) is a perennial climber, and is invasive throughout northern New Zealand. A. hortorum can out-compete and smother native vegetation, and fatally trap visiting invertebrates in the pollinarium. Because of its negative environmental impacts, wide invasive range, and high level of fecundity, A. hortorum has been described as one of the most problematic pest plants in New Zealand. High densities of A. hortorum are found in Northland and Auckland. Using an integrated approach to dispersal risk analysis, this thesis assesses the dispersal syndromes of A. hortorum and the risk of dispersal to and establishment on the islands of the Hauraki Gulf, off the east coast of Auckland. Seed terminal velocity estimates confirmed the anemochorous nature of A. hortorum, and buoyancy and seawater tolerance trials suggested the potential for thalassochorous dispersal. The windborne dispersal kernel was estimated using two models, DispeRsal and WALD, and over-sea dispersal was modelled using a particle tracker simulation (GNOME). Establishment potential was assessed using germination experiments that evaluated the germination success and growth responses of A. hortorum to substrate type, salinity exposure, and disturbance. Geospatial analyses were then used to confirm the germination trial findings, and to identify the Hauraki Gulf islands at risk of A. hortorum invasion. The results of this study suggest that all islands in the Hauraki Gulf are within dispersal reach of mainland A. hortorum populations, by anemochory, thalassochory, or both. Furthermore, germination is not strongly limited by substrate type, although a strong preference for disturbed soil was observed.
