Location/Boundaries: About 2620ha, 15km east of Mount Barker.
Assessor's Summary of Significance: The Porongurup National Park is a place of exceptional biological and ecological significance. The Park has one of the richest concentrations of plant species in Australia with more than 700 native plant species within the park of 2,621 hectares. The place is also highly endemic for a wide array of plant species, and represents an important remnant of the rich flora of south west Western Australia in a largely cleared agricultural landscape. Examples of plant groups which contribute to this outstanding richness and endemism include: heaths (Epacridaceae) especially beard-heaths (Leucopogon); peas (Fabaceae) notably flame-peas (Chorizema) and also bitter-peas (Daviesia and Bossiaea), and poison-peas (Gastrolobium); native myrtles (Myrtaceae); pimeleas (Thymelaeaceae), notably rice flowers (Pimelea); sundews and pitcher plants (Nepenthales); bloodroots, conostyles, kangaroo paws and their allies (Haemodorales); and banksias and grevilleas (Proteales). It is also important for richness in lilies, orchids and allies (Liliales), notably native lilies (Anthericaceae), irises and allies (Iridaceae), and orchids (Orchidaceae).
The Porongurup Range has acted as a refuge for invertebrate species. The granite outcrops of the Park provide damp refuges for Gondwanan relictual species, which 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. The Porongurup National Park is significant at a national scale for endemism and richness in spiders, in particular primitive trapdoor spiders (mygalomorphs). These have a Gondwanan distribution, for example some genera have a restricted distribution in Australia, but are also found in southern Africa, and are thought to be a relict of Jurassic times when Africa was joined to Australia 140 million years ago.