Alien plant invasions in relation to environmental and disturbance factors: Insights from Mediterranean Island

Abstract

Understanding the distribution patterns of invasive species and their underlying mechanisms is important for strategic planning of natural ecosystems. Our objective was to examine the distribution patterns of alien invasive plants and their environmental correlates on Rottnest Island, Western Australia. Vegetation survey was based on stratified random sample and a total of 210 plots were established to detect disturbance-environmental variables most strongly associated with spatial patterns of invasive plants. A total of 14 invasive plants belonged to seven families identified in this study. The majority of invasive plants were from the family of Poaceae, comprising six annual grasses. Trachyandra divaricata (Asphodelaceae) was the most frequent and abundance of invasive species, followed by Lagurus ovatus (Poaceae). Results highlight that Trachyandra divaricata is becoming a more significant invader and likely pose a continuing threat to the native ecosystem. GIS analysis showed the areas of high infestation linked to fire. Multivariate analysis demonstrated the presence and abundance of invasive plants along disturbance gradients (bare ground, distance to roads and fire-affected sites); signify the negative impact of fire disturbance and anthropogenic pressure on this island ecosystem. Spatial patterns of invasive alien plants from this study could assist decision makers in managing species invasions.