Phytogeography of the copper and cobalt flora of Upper Shaba (Zaire), with emphasis on its endemism, origin and evolution mechanisms

Abstract

Copper and cobalt ore deposits occur on at least a hundred outcrops scattered in the Shaban Copperbow, an area of 2 000 square kilometres, in the metallogenic Province of Southern Central Africa. With more than 200 species, this flora includes a large number (42) of endemic species of various degrees. Some species are known from only one site, many are located on neighbouring outcrops, others occur on all the ore deposits. Present migratory pathways have been traced for some species and are reported. The relative importance of palaeoendemism and neoendemism is discussed. The origin of these endemics, as well as that of other plants is to be found in several adjacent floras such as that of steppe-savannas developed on more or less poorly aerated soils (Kalahari sands or dambos overlaying laterite), dwarf vegetation on siliceous cellular rocks and miombo woodlands on poor hydromorphic soils. Examples are given for each vegetation type. Systematic details, leaf anatomy and phytogeochemistry data support these hypotheses, which are illustrated for several closely related taxa.