1. Okavango Research Institute; University of Botswana; Private Bag 285 Maun Botswana
2. USDA-ARS; Rangeland Resources Research Unit; 1701 Center Ave Fort Collins CO 80526 USA
3. Agricultural Research Council; Animal Production Institute, Rangeland Ecology; P.O. Box 7063 Nelspruit 1200 South Africa
4. UPR AGIRs; Cirad; Campus Int. Baillarguet; 34398 Montpellier cedex 5 France
5. RP-PCP; Department of Biological Sciences; University of Zimbabwe; P.O. Box MP 167 Harare Zimbabwe