Endemic to Australia, shrubs of the genus Isopogon attain their greatest diversity in Western Australia, where 27 of 35 species are found. Image credit: Peggy L. Fiedler
Southwest and South Australia have very old and weathered soils with few nutrients, much like the Cape Region of South Africa. Physical isolation from other parts of the continent due to an arid desert, plus a complex assemblage of soils and geologic formations, has produced very high plant species diversity.