A comparative study of the reproductive biology and invasive ranges of gorse (Ulex europaeus) in the Mount Lofty Ranges of South Australia and central highlands of Sri Lanka

Author: Champika Shyamalie Kariyawasam

Kariyawasam, Champika Shyamalie, 2015 A comparative study of the reproductive biology and invasive ranges of gorse (Ulex europaeus) in the Mount Lofty Ranges of South Australia and central highlands of Sri Lanka, Flinders University, School of Biological Sciences

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Abstract

Ulex europaeus L. (gorse) is a cosmopolitan invasive shrub species native to Europe. This species is classified as a ‘Weed of National Significance’ in Australia and is also recognized as an invasive species in Sri Lanka. A comparative study was conducted of U. europaeus populations located in the Mount Lofty Ranges of South Australia and central mountains of Sri Lanka. The fruit set and fruit to flower ratio, seed production per pod, seed predation and the density of gorse seeds in the upper 5 cm layer of the soil were investigated in gorse populations from late winter to spring in the Mount Lofty Ranges, South Australia and from late November to late January (late wet and early dry season) in the central mountains in Sri Lanka. The results of this study suggest that there are differences in the traits investigated in U. europaeus in their invasive range in these two countries. The threat posed by invasive alien species to native biodiversity is well recognized. Species distribution models (SDMs) are considered one of the most powerful tools to evaluate invasion risk. Forecasting the potential areas of occupancy of invasive species facilitates environmental planners taking early action, before invasive species are introduced or expand their ranges. A species’ distribution pattern may also dramatically change under different climate scenarios due to the fact that the rate of invasion by weedy species is often affected by the degree of similarity in the climate of source and reception areas. This study was conducted using the Maxent species distribution modelling software package and utilised presence-only location data to predict the potential distribution of U. europaeus in South Australia under current climate conditions. Model predictions using GLM, Bioclim, Domain and Maxent models for the same set of data were compared and Maxent was found to produce a more conservative model. Models fit in South Australia were also used to predict the climate suitability for U. europaeus of a climatically distinct area (Sri Lanka) and Maxent was identified as a robust modelling technique to make such projections. This study highlights the importance of applying a distribution model of an invasive species derived in one area to another geographic area.

Keywords: fruit : flower ratio, predation, seed bank density, seed production, Ulex europaeus, invasive species, Maxent, species distribution modelling
Subject: Biological Sciences thesis

Thesis type: Masters
Completed: 2015
School: School of Biological Sciences
Supervisor: Duncan Mackay