The south-west of Western Australia is one of only 34 internationally significant hotspots for biodiversity (Myers et al. 2000), and the Porongurup National Park is an important remnant of the flora of the south-west, with exceptional richness and endemism of species, particularly plant species. A minimum of 700 vascular plant species have been recorded within the park of 2,621 hectares, indicating a high concentration of species. (Keighery 1993, CALM 1999, ANHAT 2008). The place is one of the richest and highly endemic areas in Australia for a wide array of plant species including 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), orchids (Orchidaceae), and flax-lilies and allies (Phormiaceae) (Keighery 1993, ANHAT 2008).
The granite outcrops of the Porongurup NP provide damp refuges for Gondwanan relictual species. The Porongurup NP is significant at a national scale for endemism and richness in spiders, in particular primitive trapdoor spiders (Mygalomorphae), including trapdoor spiders (Idiopidae) brushless-legged trapdoor spiders (Migidae), two-doored trapdoor spiders (Actinopodidae), and funnel-web spiders (Nemesiidae). These have a gondwanan distribution, for example genera of the Migidae family 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 (Main 1993, ANHAT 2008).