Ungulate diversity and precipitation history since the Last Glacial Maximum in the Western Cape, South Africa

Abstract

This study reviews the precipitation history of the winter and year-round rainfall zones in the Western Cape (South Africa) in light of its fossil ungulate communities. Fossil sequences spanning the Last Glacial Maximum (LGM) and Lateglacial through the Holocene document a decline in ungulate richness through time. Based on the observed relationship between ungulate community richness and annual precipitation in Southern and East Africa, this implies increased effective precipitation during the LGM-Lateglacial at sites located in both the winter and year-round rainfall zones. These results are consistent with other lines of paleoenvironmental evidence from the winter rainfall zone, although they contradict records from the year-round rainfall zone that have been interpreted as reflecting aridity. A critical review of these records suggests that the patterns interpreted in terms of aridity can be explained by other mechanisms, including vegetation change. Current evidence is consistent with paleoclimatic models indicating that altered rainfall patterns during the LGM-Lateglacial were primarily related to the position of westerly frontal systems, which were displaced northward due to the expansion of Antarctic sea ice. Seasonal migration of these systems resulted in an expanded winter rainfall zone across much of southwestern Africa, but perhaps with some summer rains reaching the southern coast.