Evolution of two serpentine endemic taxa in Mpumalanga

Two taxa endemic to serpentine soils in Mpumalanga, Berkheya rehmannii Thel). van rogersiana Thell. and B. coddii Rossi, (Asteraceae) were selected to investigate the mode of evolution of serpentine endemics using enzyme electrophoresis. Morphological studies based on herbarium material suggested that the serpentine endemic B, rehmannii var. rogersiana is probably closely related to B. rehmannii Thell. var. rehmannii which does not grow on serpentine. The electrophoretic investigation revealed high genetic identities between all taxa studied. However, the presence of unique alleles in var. rogersiana and large differences in ailele frequencies between var. rogersiana and var. rehmannii suggest that these taxa are genetically distinct, that there is little or no gene flow between them and that they could be a progenitor-derivative pair. These data and the distribution data suggested that var. rogersiana is probably not neo-endemic nor palaeo-endemic but somewhere in between and B. coddii is probably palaeo-endemic and that they arose during independent evolutionary events. Thus, palaeo-endemism probably exists in the elements of the serpentine flora in Mpumalanga that were studied and both serpentine-tolerance and nickel accumulation have evolved more than once.