Impacts of Prosopis juliflora Linnaeus emend. Burkart on aspects of biodiversity and selected habitat conditions in Baringo Kenya

Abstract

Invasive alien species are a leading cause of biodiversity loss in the world today. In Kenya, Prosopis juliflora Linnaeus emend. Burkart is one of the most problematic invasive plant species. The origins and pattern of introduction of Prosopis juliflora into East Africa are not well known but large-scale introductions occurred in the 1980s. Little information is available on how its innate characteristics interact with the local habitat characteristics. Four hypotheses were tested to explain the effects of the invasion of P. juliflora on soil nutrient status, diversity of indigenous plant species, diversity of floral insect visitors of native Acacia spp., and how the invasive tree’s genetic diversity would relate to the rate of invasion. Plant and soil sampling was carried using modified Whittaker plots. P. juliflora density had significant influence on total organic carbon, and pH. The invasive species also had a negative effect on overall native plant species richness and density of Acacia species. This was a clear indication that P. juliflora is having an effect on the species richness of local species and that either P. juliflora is slowly replacing the indigenous Acacia species, or that the established stands of Acacia in non-disturbed conditions are a good deterrent to the encroaching P. juliflora. The results showed that P. juliflora is a preferred source of floral resources for A. mellifera during the dry season. Allozyme analysis revealed minimal genetic distance between populations. This study shows that the invasive species has negative consequences to the local ecosystem at high densities. Key words: Prosopis juliflora, Acacia species, species richness, soil properties, pollinators, genetic diversity