Journal of the Royal Society of Western Australia, 86:7-23, 2003 
Reassessment of the vascular flora of Rottnest Island 
E Rippey, 1,2 M C Hislop, 3 & J Dodd 14 
1 Rottnest Voluntary Guides Association, Rottnest Island, WA 6161 
2 Department of Geography, University of Western Australia, Crawley, WA 6009 
3 jjrippey@cyllene.uvva.edu.au 
3 WA Herbarium, George Street, Kensington, WA 6151 3 mikeh@calm.wa.gov.au 
4 Department of Agriculture, Baron-Hay Court, South Perth, WA 6151 
3 jdodd@agric,wa.gov.au 
(Manuscript received March 2002; accepted December 2002) 
Abstract 
A survey of the vascular flora of Rottnest Island, carried out between 1998 and 2001 with the 
aim of recording all native and introduced species, was compared with previous lists, and the 
nomenclature was reconciled and updated. A total of 246 native and introduced species have been 
recorded for the island, of which 196 species were found in 1998-2001. A survey in the late 1950s 
had recorded a similar total number of species (201) but the proportion of native species had 
dropped over the period between censuses from 62% in the 1950s to 58% in 1998-2001. Despite the 
relatively constant species total, the flora of Rottnest is dynamic, with 44 species known to have 
been present in the late 1950s not recorded at the end of the century, while 38 additional species 
were found in 1998/2001, giving a rate of turnover of 1% pa. In this paper, an annotated flora list of 
246 recorded species is given as well as a list of 122 deleted names, with reasons for their exclusion 
from the flora list. Thirty-five cultivated species collected from outside of gardens, but which had 
not become naturalised, are listed separately. 
Keywords: vascular flora, Rottnest Island, species turnover rate, immigration, extinction, island 
biogeography 
Introduction 
Rottnest Island has been the subject of intensive 
biological research due to its diversity of marine and 
terrestrial habitats, and its proximity to Perth-based 
research centres (Hodgkin & Sheard 1959; Bradshaw 
1983; Huisman & Walker 1990; Wells et al 1991; Walker 
& Wells 1996). As a result, much of the island's 
biodiversity has been documented. 
It was during the 1950s that the first in-depth botanical 
explorations took place. McArthur (1957) compared the 
flora of Rottnest, Carnac and Garden Islands. Storr (1962) 
published a more complete annotated list of the Rottnest 
Island flora that formed the basis for subsequent floristic 
lists, specifically those of O'Connor (1977) and Frewer et 
al (1985). These latter accounts accepted much of the 
information reported by Storr (1962) but included some 
changes in nomenclature and added a few new 
observations. Marchant & Abbott (1981) reviewed 
previous surveys and listed those species recorded for 
Rottnest and Garden Islands, and updated the 
nomenclature. Also available was a list of specimens 
from Rottnest Island lodged with the Western Australian 
Herbarium prior to 21 st May 2001. 
There were no major disturbance events on Rottnest 
Island from 1955 to the end of the twentieth century. The 
quokka ( Setonix brachyurus) population remained at 
saturation level, fires were prevented or rapidly 
controlled, and the island was run as a conservation 
reserve for recreation and tourism. Under this regime 
© Royal Society of Western Australia 2003 
tree species have been unable to regenerate naturally and 
a depauperate, sclerophyllous grassy heath has become 
the most widespread community on the island. This 
consists mainly of Acanthocarpus preissii and Austrostipa 
flavescens (Hesp et al. 1983), although the exotic geophyte 
Trachyandra divaricata has become an important 
constituent, having spread since the 1950s when it 
seldom occurred away from coastal dunes (Storr 1962). 
Between 1998-2001 the Rottnest Voluntary Guides 
collected about 400 specimens of vascular plants, to 
establish the Rottnest Regional Herbarium (RRH). 
Identification by the Western Australian Herbarium of 
RRH specimens provided the basis for reconciling 
previously published lists, and enabled the size and 
composition of the flora to be re-assessed. This paper 
thus provides the first specimen-based list of the vascular 
plants of Rottnest Island. 
Methods 
All native and naturalised vascular species were 
targeted for the Rottnest Regional Herbarium, including 
aquatic angiosperms from the salt lakes, freshwater 
swamps and surrounding ocean. The plants of two islets 
off Rottnest Island, Dyer and Green, and Little Island in 
Lake Baghdad, were included. Cultivated trees and 
shrubs growing outside (but not inside) fenced gardens 
were also collected. All major habitats including the 
Settlement, woodlands, salt lakes, swamps, heathlands, 
and coastal areas were visited several times, at different 
seasons. Efforts were made to include differing 
topographical features within these areas, such as hills, 
rocky outcrops, swales and headlands. 
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