Borassus aethiopum Mart. (Arecaceae) in Limpopo province with a key to South African palms

Abstract

Background: Borassus aethiopum Mart. commonly occurs in many parts of tropical Africa and in South Africa it is restricted to the Leydsdorp region where it is conspicuous along the Selati River. The species is sometimes considered to have been introduced to South Africa due to its disjunct distribution. It has remained poorly studied and little is known about the local populations of this palm.Objectives: This study provides a descriptive treatment and documents the population structure of B. aethiopum in this area, and presents a key to the six indigenous palm species of South Africa.Methods: All accessible populations were surveyed and documented, and eight transects were randomly placed to gather data on size class distributions. B. aethiopum and other indigenous palm species were compared morphologically.Results: The population structure analyses of B. aethiopum revealed a monotonic decline, but the permutation index suggested that the species is prone to recruitment events. This is supported by patches that are dominated by specific height classes. Leaf shape and size, fruit size and geographical distribution were the diagnostic characters most useful to recognize the species of South African indigenous palms.Conclusion: Borassus aethiopum is distinguishable from other South African palms based on stem, leaf and fruit characters. It is considered as indigenous to Granite Lowveld as the palm is part of the natural vegetation and is characterized by a size class distribution reflecting a stable population.