On the Island Origin of the Endemic Trees of the British Guiana Peneplain

MANY of the commonest trees in the rain forests of British Guiana are either endemic or confined to the Guiana region. A few have a still more limited range, and occur only in certain groups of hills and their immediate neighbourhood. In other continental tropical regions, e.g. Nigeria, most of the common trees have a wide geographical distribution. Mr Smith Bracewell, the Director of the Geological Survey of British Guiana, and the writer have come independently to the conclusion that the probable explanation why some Guiana trees have such a limited range is that they were once endemic in particular groups of islands at a time when the greater part of the present land surface was submerged, and volcanic islands now represented by hills were the only areas of dry land in the region. If this theory is correct it also explains the distribution of endemic species with a wider range; and its application may be expected to extend to other countries with a similar geological history.