Environmental heterogeneity explains contrasting plant species richness between the South African Cape and southwestern Australia

Aim: To assess whether a difference in species richness per unit area between two mediterranean-type biodiversity hotspots is explained by differences in environmental heterogeneity.

Location: The Greater Cape Floristic Region, South Africa (GCFR) and Southwest Australian Floristic Region (SWAFR).

Taxon: Vascular plants (tracheophytes).

Methods: Comparable, geospatially explicit environmental and species occurrence data were obtained for both regions and used to generate environmental heterogeneity and species richness raster layers. Heterogeneity in multiple environmental variables and species richness per unit area were compared between the two regions at a range of spatial scales. At each scale, richness was also regressed against these individual axes and against a major axis of heterogeneity, derived by principal component analysis (PCA).

Results: The GCFR is generally more environmentally heterogeneous and species-rich than the SWAFR. Species richness per unit area is ...