Convergence and non‐convergence of plant traits in climatically and edaphically matched sites in Mediterranean Australia and South Africa

Abstract

Abstract This paper compares the occurrence of plant traits in five edaphically matched sites at the Barrens, southwestern Australia and the Agulhas Plain, southwestern South Africa. The two regions are very closely matched in terms of their Mediterranean‐type climates, landforms, soil types and disturbance regimes. On both continents, matched sites on all substrata (siliceous sand, quartzite, laterite, limestone and calcareous sand) support sclerophyllous shrublands with a similar mix of growth forms. Soils from all substrata in both Australia and South Africa are extremely nutrient‐poor except for the calcareous sands where high levels of phosphorus were recorded. Contrary to expectations, Australian soils are not generally less fertile than their South African counterparts. The frequency of species in different leaf consistence categories was similar on the two continents, as was the leaf specific mass of overstorey shrubs from all substrata. Woody plants with leaf spines are significantly more frequent on Australian nutrient‐poor substrata. Among woody plants, species with canopy‐stored seed are significantly more frequent on Australian nutrient‐poor sites, whereas species with bird‐dispersed fruits and inter‐fire germination are significantly more frequent on South African limestone and calcareous sand. There was good evidence for convergence between the two continents in the frequency of other seed biological traits. The study indicates strong convergence between Australian and South African shrublands in the frequency of a wide range of traits relating to plant form and function. Examples of non‐convergence are probably due to regional and historical processes rather than differences in the contemporary physical environments of the two study areas.