Nickel Hyperaccumulation in the Serpentine Flora of Cuba

Extraordinary uptake (hyperaccumulation) of nickel (Ni), reaching concentrations of 0n1-5n0 %, about 1000-times greater than those usually found in flowering plants, has been reported over the period 1948-1996 in about 190 species that grow on Ni-rich serpentine soils derived from ultramafic rocks in various parts of the world. A recent study of the families Buxaceae and Euphorbiaceae identified a further 80 Ni hyperaccumulators from the very large ultramafic flora of Cuba, the largest number found to date in any one country. A much wider investigation of the elemental content of plants from the Cuban ultramafic flora, reported here with representative analyses of the corresponding soils, has revealed Ni hyperaccumulation in an additional 50 taxa (in 16 genera and eight families). The number of hyperaccumulators is greatest on the oldest serpentine soils, which are believed to have been available for colonization for the last 10-30 million years. Both Ni hyperaccumulators, and serpentine endemic species generally, are much more frequent on these old soils, occurring in the eastern and western extremities of Cuba, than on those developed within the last million years in the central part of the country. Hyperaccumulating plants of the families Acanthaceae, Asteraceae, Clusiaceae, Myrtaceae, Ochnaceae, Oleaceae, Rubiaceae and Tiliaceae are discussed.