The relations between the South African fauna and the terrestrial and limnic animal life of the southern cold temperate zone

Abstract

In principle, the fauna of the southern temperate zone should present a general distribution pattern similar to that of the northern temperate zone. The rich invertebrate material preserved in the early Tertiary Baltic amber indicates that, at that time, the similarity was much closer than it is today. But during the Tertiary the cooling climate, in the north, resulted in the recession and extinction of many of those organisms which were rigidly fixed to a certain combination of environmental factors. The Pleistocene glaciations very effectively put a stop to the existence of many such invertebrate species and species groups whose relatives are now regarded as typical relicts. There is no doubt that the influence of the ice ages was comparatively small in the southern temperate zone of the Old World compared to what happened in the north. As regards the African continent it has been supposed that the highest areas in southern Africa, the Maluti Range in eastern Basutoland, at that time were covered with ice. But it was not so. On visiting that area we found that it has been free from ice, and moreover, that it is inhabited by an interesting, largely endemic fauna. Likewise, there is nothing indicating that the South Atlantic islands, the Tristan group and Gough Island, were capped with ice or carried isolated glaciers during the Pleistocene glaciations. Comparatively unchanged climatic conditions made the survival of the preglacial fauna possible.