An assessment of Prosopis L. in the Bokspits Area, South-Western Botswana, based on Morphology

Abstract

The genus Prosopis comprises 44 species. Extensive introgression and hybridization is suspected in the genus, which makes identification of the species very difficult. Accurate identification of the species is crucial in controlling invasive species, within this genus. That is so because the method of control is species specific. The objective of the study was to determine the taxonomic structure of Prosopis species in Southern Botswana. A systematic qualitative approach was used to sample the species such that specimen selection was based on observable morphological discontinuities. The morphological characters were subjected to multivariate analysis since the analysis has been reported to be good at identifying hybrids. The multivariate analysis included anova, cluster analysis, factor analysis and canonical correlation. The study revealed four pure lines of Prosopis and nine hybrid species. The pure lines are Prosopis chilensis, P. juliflora, P. velutina and P glandulosa and they all belong to one section, ALGAROBIA. The observed hybrids were P. chilensis x P. glandulosa, P. glandulosa x P. chilensis, P. juliflora x P. glandulosa, P. chilensis x P. juliflora, Acacia karroo x P. juliflora, P. glandulosa x P. pallid, P. juliflora x P. pallid, P. chilensis x P. juliflora x P. glandulosa and P. chilensis x P. pallida. It was therefore concluded that the Prosopis species in Southern Botswana have formed a hybrid swam. And for the hybrids P. chilensis x P. glandulosa and P. glandulosa x P. chilensis it was concluded that gene flow between P. chilensis and P. glandulosa is bidirectional. For the hybrid P. juliflora x P. glandulosa it was concluded that gene flow was from P. juliflora to P. glandulosa.