The Distribution of Epizoochoric Plant Species: A Clue to the Prehistoric Use of Arid Karoo Rangelands by Large Herbivores

Abstract

Adhesive dispersal mechanisms are rare in the defence against large mammalian herbivores and is not flora of the plains of the arid south-western Karoo, South adapted for using these animals as seed dispersers. We Africa, and most plants lack the long or hooked thorns postulate that in prehistoric times the resident vertebrate normally associated with defence against browsing mam- herbivores of this area were mainly small mammals with mals on nutrient-rich soils. The flora of drainage lines, limited home ranges; avian herbivores and large browsing however, differs from that of the surrounding flats in that mammals being restricted to the taller vegetation of many of its species are thorny, bear pods or succulent fruits drainage lines. The grassier northern and eastern Karoo, palatable to mammals, and more species have adhesive with its thorny trees and shrubs and barb-fruited grasses, propagules. The few adhesive fruits that are found in dom- probably provided permanent forage for herds of large estic Merino sheep fleeces in the arid Karoo belong to alien ungulates which occasionally extended their ranges south- species, annual grasses, and plants of drainage lines. westwards, after relatively high rainfall periods had pro- Fleeces from the higher rainfall, grassier eastern and north- moted improved forage in the arid Karoo. ern parts of the Karoo carry many more adhesive diaspores,