THE EVOLUTIONARY EFFECTS OF METALLIFEROUS AND OTHER ANOMALOUS SOILS IN SOUTH CENTRAL AFRICA.

Abstract

The extensive metalliferous and other anomalous soils of South Central Africa have been in existence since before the origin of the angiosperms. So, they should have provided situations in which evolution could have continued uninterrupted, except by major climatic changes, over very long periods. The floras on these areas have therefore been examined, and compared to the situation in Northern Europe. The African anomalous floras could be expected to show: (a) a larger number of species which occupy the anomalous soils; this is certainly true; (b) a greater distinctiveness of the populations tolerating the anomalous soils; there is only a little evidence for this; (c) a greater number of tolerant populations which have attained the status of distinct endemic species but which have close relatives; there are a few examples of these; (d) a greater number of tolerant endemic species which have lost their close relatives; there are quite a large number of these, some specific to individual areas of a particular type of anomalous soil. The greater number of endemics is a definite characteristic of the floras. However, despite their great stability, the anomalous areas are not occupied by a flora consisting mostly of endemic species. It is clearmore » that many of the plant populations on the areas must be of recent origin. This suggests that there have been sufficient climatic and other changes to eliminate many of the original colonists and allow the immigration of others.« less