Stirling Range National Park is one of the top ranking places across Australia for biodiversity. The place represents one of the most important remnants of the rich flora of the south-west, in an area that is predominantly cleared for agriculture. The Stirling Range provides an example of the extraordinarily diverse flora of the south-west, and over 1500 species have been recorded in the Park, which represents almost one fifth of all the flora species found in the south-west. The Stirling Range also exemplifies the abundance of endemic species found in the south-west, with 87 species being found solely within the Park. The Stirling Range is one of the most important areas in Australia for eucalypt richness and endemism. Examples of other plant groups which are of outstanding richness and endemicity at Stirling Range include the epacrids, the Fabaceae (the peas), and genera within the Myrtaceae, including Darwinia (mountains bells), Melaleuca, and Verticordia (feather flowers). The Stirling Range also has particularly high species richness and endemicity within the Proteaceae, including for dryandras, banksias, and hakeas. Stirling Range has a diverse array of relict endemic invertebrates, many of which are recognised as Gondwanan, and many of the species here are more closely related to groups in mountainous areas of eastern Australia, Tasmania, New Zealand and other Gondwanan continents, than to the surrounding lowlands in the region. Deeply incised south-facing gullies provide refuge for Gondwanan relictual species such as ancient trapdoor spider species (mygalomorphs), and species of land snail, and other relict invertebrate species, including scorpions, pseudoscorpions, earthworms and primitive isopod crustaceans. The Stirling Range is one of most important areas in Australia for endemic mygalomorph species, and is also one of the richest areas for land snails, particularly within the Bothriembryon genus. The richness of land snails is significant not only in itself, but because land snails have been demonstrated as an indicator species of areas of moist refugia over long periods.