Did the flora match the fauna? Acocks and historical changes in Karoo biota

Abstract

Years of observation in Karoo veld convinced JP Acocks that the perennial grasses that he occasionally encountered in barren Karoo landscapes were remnants of pre-colonial vegetation. He maintained that desertification, caused by overgrazing and alteration of drainage systems, had destroyed key grazing resources, reducing the carrying capacity of the vegetation for large herbivores. We attempt to test this notion by reconstructing the fauna for sample areas of the Karoo from farm names, plant common names and travellers records, and by examining the flora of these areas for evidence of co-evolution with large herbivores. We concluded that names of mapped features and farms that refer to animals do reflect the historical distribution of these animals. However, within Karoo sampling units of approximately 500 km2, we could find no close relationship between historical records of large herbivores and herbivore-adapted defence and dispersal traits of plants. This weak evidence for co-evolution might have been because many of the large herbivores were not permanent residents in the Karoo. Alternatively it might be an artefact caused by lack of abundance data for plant guilds. There is evidence that post-colonial land use of the Karoo has changed vegetation structure and productivity within the areas we sampled.