JournalJournal of theof the Royal Royal Society Society of Westernof Western Australia, Australia, 80(3), 80:141-158, September 1997 1997 Plants of Western Australian granite outcrops S D Hopper1, A P Brown2 & N G Marchant3 1Kings Park and Botanic Garden, West Perth WA 6005 email:
[email protected] 2Western Australian Threatened Species & Communities Unit, Department of Conservation and Land Management, PO Box 51, Wanneroo WA 6065 email:
[email protected] 3Western Australian Herbarium, Department of Conservation and Land Management, PO Box 104, Como WA 6152 Abstract Outcropping granite rocks in Western Australia span a considerable climatic range, from the mediterranean south-west to inland desert and northern arid subtropics and tropics. At least 1320, and possibly 2000, plant taxa occur on Western Australian granite outcrops. Outcrop plant life is most diverse in the South West Botanical Province, with individual outcrops having up to 200 species, including many endemics not found in surrounding habitats. Species richness and local endemism declines with increasing aridity, to the point where Kimberley and Pilbara outcrops show little discontinuity in species from the surrounding landscape matrix. Outcrops are dominated by woody and herbaceous perennials, especially of the Myrtaceae, Orchidaceae, and Mimosaceae, and have an unusually rich diversity of annuals (Asteraceae, Stylidiaceae, Poaceae, Amaranthaceae etc.) compared with the flora as a whole. An unusual life form is found in resurrection plants capable of extreme desiccation and rehydration (e.g. Borya, Cheilanthes). Among woody perennials, bird pollination is frequent, and some outcrops harbour a high proportion of obligate seeder species due to the refuge from fire provided by bare rock barriers.