Selection of medicinal plants - Evolutionary considerations for ethnopharmacology and drug discovery

Biological diversity is evidence for chemical diversity. Secondary metabolites are adaptive traits, similar within members of a taxon and occasionally also between taxa exposed to similar ecological selection pressures. Chemo diversity is thus not distributed evenly across plant biodiversity. But how are biodiversity, drug discovery, traditional medicines and ethno pharmacology related? Only 62 out of a total of 457 Angiosperm and Gymnosperm plant families are used as a source for biomedical drugs (Zhu et al., 2011, PNAS). Plant taxa used in traditional and local medicines belong to an over-proportional extent to the same 62 families. A cross-check with the Angiosperm Phylogeny Website showed that these 62 families are over-proportionally species-rich and widespread. We hypothesized that as a function of evolution, widespread taxa contain a broader range of ecological information encoded in their genes with respect to taxa with a local evolution history (Leonti et al., 2013, JEP). We argued that as a consequence widespread taxa synthesize metabolites with a wider ecological than taxa with a geographically limited geographical distribution.