Rhizobia diversity and their effect on the distribution of indigenous legumes in the Cape Floristic Region

Abstract

The Cape Floristic Region (CFR) includes a broad variety of bed rocks and soils are a mosaic of sandstone and shale substrates that give rise to a variety of soil types mainly sandstone, aeolian sands, shale, granite and limestone thereby creating heterogeneity in edaphic conditions. Species composition of plant communities in the CFR is predominantly associated with the parent rock, and the resultant overlying soil. The combination of edaphic and topographical variations, local climate gradients and frequent fires is undoubtedly important in promoting species diversity in the region. The family Fabaceae is the second largest family to Asteraceae in the CFR. It is currently comprised of about 760 species, in 37 genera belonging to 18 tribes. Most of these legumes are in symbiotic association with rhizobia that nodulate and fix nitrogen in the nutrient poor soils...It was, therefore, hypothesized that rhizobia isolates from indigenous legumes of the CFR will cluster phylogenically according to soil types and that the distribution of rhizobia limited that of their compatible host.