Biogeography of Stylosanthes capitata Vog. and Stylosanthes guianensis Sw. var. pauciflora

Abstract

The natural distribution of Stylosanthes capitata and S. guianensis var  pauciflora is almost identical, and is concentrated is the Central-West, Southeast and Northeast regions of Brazil, and in the Northeast of Venezuela. The present germplasm coilections comprise 350 and 250 accessions respectively, collected on sandy and acid soils of low fertility, principally in savanna ecosystems characterized by 900-1,800 mm of anual rainfall and 4 to 6 dry months. S. capitata extends also into semi-arid regions; S. guianensis var. pauciflora into higli-rainfall zones. Six distinct morphological groups are identified for S. capitata. The need for systematic evaluations of both species' collections is discussed, with the objective to establish possible relationships between ecological conditions in the regions of germplasm origin and the eventual agronomic performance of accessions, and to set priorities for further germplasm collecting missions.