Bioprospecting: evolutionary implications from a post-Olmec pharmacopoeia and the relevance of widespread taxa

Ethnopharmacological relevance: ‘‘Nothing in biology makes sense except in the light of evolution’’ 1 The historical legacy and relevance of ethnopharmacology in drug discovery is undisputed. Here we connect the parameters influencing the selection of plant derived medicines by human culture with the concept of evolution. Aim of the study: In the present contribution we compare global data with local data and try to answer the questions, to what extent are the taxonomic clades included in indigenous pharmacopoeias associated with certain ailment groups, and to what extent can ecology and phylogeny, which we consider a proxy for chemical relatedness and convergence, account for the observed bias? Materials and methods: We use an approximated chi-square test (w2) to check for associations between 12 ethnomedical use-categories and 15 taxonomical clades. With cluster analyses we test for correlations between phylogeny and use-categories. We compare the 67 drug-productive families identified by Zhu et al.,2 with the medicinal flora of the Popoluca and the APG database and compare our results with the phylogenetic target classes evidenced by Zhu et al. Furthermore, we compare the medicinal flora of the Popoluca with the world’s weeds (cf. Holm et al.)3 and discuss our results in relation to anthropological rationales for plant selection. Results: The null-hypothesis ‘‘species from the 15 taxonomic clades are selected proportionally to their share in the treatment of the twelve organ- and symptom-defined use-categories’’ is rejected. The cluster dendrogram for the clades shows that the use patterns are to a certain extent associated with Angiosperm phylogeny. With the occurrence of 53 families the 67 drug-productive families are overrepresented in the regional flora of the Popoluca. The importance of these families in terms of their share is even more pronounced with the medicinal flora holding around 70% of all individual Popoluca informant responses. Conclusions: The overall phylogenetic use pattern is influenced by both the inherent pharmacological properties, which depend on phylogeny, biogeography, ecology and ultimately allelopathy, and on culture-specific perception of organoleptic properties. The comparison of the 67 drug-productive Viridiplantae families with the ethnopharmacopoeia of the Popoluca and the APG database, shows that ‘‘traditional’’ pharmacopoeias and plant-derived drugs are obtained from widespread and species-rich taxa. This is not a function of family size alone. We put forward the theory that as a function of evolution, widespread taxa contain a broader range of accumulated ecological information and response encoded in their genes relative to locally occurring taxa. This information is expressed through the synthesis of allelochemicals with a wide ecological radius, showing broad-spectrum biotaspecific interactions, including the targeting of proteins of mammals and primates.