Why do people use exotic plants in their local medical systems? A systematic review based on Brazilian local communities.

Efforts have been made to understand the processes that lead to the introduction of exotic species into local pharmacopoeias. Among those efforts, the diversification hypothesis predicts that exotic plants are introduced in local medical systems to amplify the repertoire of knowledge related to the treatment of diseases, filling blanks that were not occupied by native species. Based on such hypothesis, this study aimed to contribute to this discussion using the context of local Brazilian populations. We performed a systematic review of Brazilian studies up to 2011 involving medicinal plants, excluding those studies that presented a high risk of bias (because of sampling or plant identification problems). An analysis of similarities (ANOSIM) was conducted in different scales to test for differences in the repertoire of therapeutic indications treated using native and exotic species. We have found that although there is some overlap between native and exotic plants regarding their therapeutic indications and the body systems (BSs) that they treat, there are clear gaps present, that is, there are therapeutic indications and BSs treated that are exclusive to exotic species. This scenario enables the postulation of two alternative unfoldings of the diversification hypothesis, namely, (1) exotic species are initially introduced to fill gaps and undergo subsequent expansion of their use for medical purposes already addressed using native species and (2) exotic species are initially introduced to address problems already addressed using native species to diversify the repertoire of medicinal plants and to increase the resilience of medical systems. The reasons why exotic species may have a competitive advantage over the native ones, the implications of the introduction of exotic species for the resilience of medical systems, and the contexts in which autochthonous plants can gain strength to remain in pharmacopoeias are also discussed.

The use of different indicators for interpreting the local knowledge loss on medical plants

ABSTRACT The increasing loss of local ecological knowledge may have negative impacts on the resilience of socio-ecological systems and may also negatively impact bioprospecting efforts, since local ecological knowledge is an important source of information for searching new drugs. Recent studies try to evaluate whether communities are experiencing loss of local ecological knowledge. However, some of them make conclusions which are erroneously based on specific analyses of a single indicator. We propose an integrative analysis of three indicators, namely: number of plants cited by young people and elders, therapeutic choices and people's connectance in terms of medicinal plant learning. The study was carried out in the community of Sucruiuzinho (Bahia, Brazil). We conducted semistructured interviews and a therapeutic recall with 24 local dwellers. We did not find evidence of local ecological knowledge loss in the studied community. Although younger people know fewer plants, they are well connected in terms of knowledge transmission. Moreover, in illness events, young people and adults have similar proportions of choice for plants when compared to allopathy. Concomitant use of the three indicators leads to a more realistic scenario of local ecological knowledge loss than the use of only one of them.