Patterns of plant diversity and endemism in Namibia

Abstract

Species richness, endemism and areas that are rich in both species and endemic species were assessed and mapped for Namibia. High species diversity corresponds with zones where species overlap. These are particularly obvious where there are altitudinal variations and in high-lying areas. The endemic flora of Namibia is rich and diverse. An estimated 16% of the total plant species in Namibia are endemic to the country. Endemics are in a wide variety of families and sixteen genera are endemic. Factors that increase the likelihood of endemism are mountains, hot deserts, diversity of substrates and microclimates. The distribution of plants endemic to Namibia was arranged in three different ways. Firstly, based on a grid count with the phytogeographic value o f the species being equal, overall endemism was mapped. Secondly, range restricted plant species were mapped individually and those with congruent distribution patterns were combined. Thirdly, localities that are important for very range-restricted species were identified. The resulting maps o f endemism and diversity were compared and found to correspond in many localities. When overall endemism is compared with overall diversity, rich localities may consist of endemic species with wide ranges. The other methods identify important localities with their own distinctive complement of species.