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Aim Ecologically driven diversification can create spectacular diversity in both species numbers and form. However the prediction that the match between intrinsic (e.g. functional trait) and extrinsic (e.g. climatic niche) variables may lead to evolutionary radiation has not been critically tested. Here we test this hypothesis in the Southern Hemisphere plant family Proteaceae which shows a spectacular diversity in open mediterranean shrublands in the Southwest Australian Floristic Region (SWAFR) and the Cape Floristic Region (CFR). Proteaceae occupies habitats ranging from tropical rainforests to deserts and is remarkably variable in leaf morphology. Location Southern Hemisphere. Methods We built a phylogeny for 337 Proteaceae species (21 of total) representing all main clades climatic tolerances and morphologies and collected leaf functional traits (leaf area sclerophylly leaf shape) for 261 species and climatic niche data for 1645 species. Phylogenetic generalized least squares regression and quantitative trait evolutionary model testing were used to investigate the evolutionary pathways of traits and climatic niches and their effect on diversification rates. Results We found that divergent selection may have caused lineages in open vegetation types to evolve towards trait and climatic niche optima distinct from those in closed forests. Furthermore we show that the interaction between open habitats dry warm and/or mediterranean climates and small sclerophyllous toothed leaves increases net diversification rates in Proteaceae. Main conclusions Our results suggest that the evolution of specific leaf adaptations may have allowed Proteaceae to adapt to variable climatic niches and diversify extensively in open ecosystems such as those in the CFR and SWAFR. This match between morphology and environment may therefore more generally lead to evolutionary radiation.