The role of exotic species in traditional pharmacopeias of the Cerrado: a case study in Southeast Brazil.
The "diversification hypothesis" proposes that exotic species are incorporated into plant pharmacopeias to broaden the range of treatments and meet therapeutic demands unattended by native species. The "versatility hypothesis" suggests that the wider range of uses of exotic species explains their selection in traditional pharmacopeias. This study was conducted with experts in medicinal plants in the Cerrado (Brazilian savanna), selected through the "snowball" technique, to test if the versatility and diversity hypotheses explain the incorporation of exotic species in the popular pharmacopeia. Relative importance (RI) index was calculated for each species, as a measure of versatility. A variance analysis was performed to compare RI of native and exotic species. An analysis of similarity (ANOSIM) was used to test the differences among the types of therapeutic indication and the ICD-10 body systems, by native and exotic species. The local pharmacopeia has 108 native and 32 exotic species for the treatment of 52 health issues. The results do not support the versatility hypothesis, since native and exotic species have similar RI. However, the repertoire of native species tends to be more versatile, being suitable for treating a wider range of disorders. In spite of the overlap of native and exotic species in therapeutic indications, some exotic species are unique to the treatment of certain diseases, effectively strengthening the local pharmacopeia and thus supporting the diversification hypothesis.