The Southwest Australian Floristic Region: Evolution and Conservation of a Global Hot Spot of Biodiversity

TLDR

The Southwest Australian Floristic Region is a Mediterranean‑climate biodiversity hotspot with ~7,380 native vascular plants, 49 % endemic, and 2,500 species of conservation concern, whose complex evolutionary history involves multiple Cretaceous–Cenozoic dispersal events, rapid speciation, and the persistence of ancient lineages on nutrient‑poor, weathered soils. The study recommends that conservation efforts minimize soil disturbance and employ locally sourced germplasm for restoration to preserve the region’s unique flora. Despite its rich flora, the SWAFR’s species are highly threatened by European land‑use practices on these ancient landscapes.

Abstract

▪ Abstract Like South Africa's Greater Cape Floristic Region, the Southwest Australian Floristic Region (SWAFR) is species rich, with a Mediterranean climate and old, weathered, nutrient-deficient landscapes. This region has 7380 native vascular plants (species/subspecies): one third described since 1970, 49% endemic, and 2500 of conservation concern. Origins are complex. Molecular phylogenies suggest multiple dispersal events into, out of, and within the SWAFR throughout the Cretaceous and Cenozoic; in many phylogenetically unrelated clades; and from many directions. Either explosive speciation or steady cladogenesis occurred among some woody sclerophyll and herbaceous families from the mid-Tertiary in response to progressive aridity. Genomic coalescence was sometimes involved. Rainforest taxa went extinct by the Pleistocene. Old lineages nevertheless persist as one endemic order (Dasypogonales) and 6–11 endemic families. Such a rich flora on old landscapes that have been exposed to European land-use practices is highly threatened. Conservation programs must minimize soil removal and use local germplasm in restoration programs.