Abstract
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.
Highlights
In ethnobiology, an interesting model to study the evolutionary dynamics of cultural systems is the process of incorporation of exotic plants into local medical systems
We propose the following questions: (1) Is there a tendency of exotic species to be used for the treatment of a set of different diseases than those treated by native species in the different Brazilian ecosystems? (2) Do exotic species occupy gaps in pharmacopoeias that are not filled by native species? The answer to these questions may help in eliciting the advantages and disadvantages of the incorporation of exotic species in local medical systems, which can guide public policies regarding the valorization of native species and the maintenance of local traditions
Hypotheses explaining the inclusion of exotic species in pharmacopoeias The results do not support a clear division between the contribution of native and exotic species regarding the repertoire of diseases treated by medicinal plants
Summary
An interesting model to study the evolutionary dynamics of cultural systems is the process of incorporation of exotic plants into local medical systems. The rapid spread of allochthonous species into traditional medical systems has generated concerns based on associations of this phenomenon with the loss or erosion of knowledge. These interpretations should be viewed with caution because we often ignore that knowledge systems are dynamic and contain a strong adaptive component [4]. Palmer [5] noted the occurrence of a loss in the number of native species used in the local pharmacopoeia and an increase in the number of introduced plants in a study conducted in Hawaii The author attributed those changes to an adaptive behavior in response to ecological and cultural changes. Would those changes be negative for the communities or an adjustment that expands the ability of people to interact with the environment? Does the widespread use of exotic species contribute to the resilience of local medical systems [6]?
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