CONVERGENCE AND NON-CONVERGENCE OF PLANT TRAITS IN CLIMATICALLY AND EDAPHICALLY MATCHED SITES IN MEDITERRANEAN AUSTRALIA AND SOUTH-AFRICA

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 mat ched in terms of their Mediterranean-type climates, landforms, soil ty pes and disturbance regimes. On both continents, matched sites on all substrata (siliceous sand, quartzite, laterite, limestone and calcareo us sand) support sclerophyllous shrublands with a similar mix of growt h forms. Soils from all substrata in both Australia and South Africa a re extremely nutrient-poor except for the calcareous sands where high levels of phosphorus were recorded. Contrary to expectations, Australi an soils are not generally less fertile than their South African count erparts. The frequency of species in different leaf consistence catego ries 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 significantl y more frequent on Australian nutrient-poor sites, whereas species wit h bird-dispersed fruits and inter-fire germination are significantly m ore frequent on South African timestone and calcareous sand. There was good evidence for convergence between the two continents in the frequ ency of other seed biological traits. The study indicates strong conve rgence between Australian and South African shrublands in the frequenc y of a wide range of traits relating to plant form and function. Examp les of non-convergence are probably due to regional and historical pro cesses rather than differences in the contemporary physical environmen ts of the two study areas.