Some Factors Inducing Change in the Vegetation of Rottnest Island

Abstract

Rottnest Island is a small island off the coast of Western Australia opposite the City of Perth. Its flora includes 180 species of vascular plants of which 63 species are exotic. Most of these are winter annuals. About 130 years ago a penal colony for aborigines was established with accompanying agriculture for a self sufficient colony. This was abandoned about 40 years ago and the land was settled with the addition of livestock to the native animal population. Quokkas (Setonix brachyurus), or the short-tailed wallaby, are the most important native animal. Original vegetation included as dominants a species each of Callitris, Melaleuca and Pittosporum. With the removal of these trees for lumber, Acacia rostellifera replaced them as the woody dominant and formed dense thickets. The quokka seems to prefer the acacia as a food plant and as a result of checks on its predation by humans is increasing, reversing the advantage that was enjoyed previously by the acacia. || ABSTRACT AUTHORS: W. Bridge Cooke