We analysed leaves from 42 plants from the South African Succulent Karoo. Whole leaf d 13 C values clearly differentiated 3 different populations, consisting of plants operating under obligate CAM (crassulacean acid metabolism), facultative CAM and C 3 modes. In contrast, the leaf wax n-alkane d 13 C data from these metabolic groups showed a broader overlapping distribution. CAM plants operating under full CAM mode produced a wide range of apparent 13 C fractionation. Succulent/CAM plant wax yield was considerable (up to 23 mg/g in our plants), so its contribution to soil composition and sedimentary leaf wax composition should not be dismissed. The presence of CAM plant wax n-alkanes in sedimentary n-alkanes could therefore be a problem for accessing ecosystem scale C 3 –C 4 proportion.