Stylosanthes is a mainly Neotropical legume genus. South America is considered as the main centre of diversity of Stylosanthes species whose centre of origin probably lies also here. Stylosanthes is of economic importance; currently, some species are used in Australia, tropical Asia, sub-Saharan Africa and tropical America as forage, soil cover, for soil improvement and for the production of concentrate feed for livestock. The genus comprises about 25 species but in the literature estimates of up to 50 species can be found. This is a consequence of the high morphological plasticity of Stylosanthes species leading to uncertainties regarding species delimitation. Differences among Stylosanthes taxonomical revisions are due to the respective author¿s species concept, i.e., based on floral morphology versus vegetative characters. An example of such different viewpoints is the so-called Stylosanthes guianensis complex where most members are treated as separate species by some authors and as botanical varieties by others.