Ecological Theories and Major Hypotheses in Ethnobotany: Their Relevance for Ethnopharmacology and Pharmacognosy in the Context of Historical Data

The cross-cultural exchange of plant resources between societies across the globe added to the diversification of medicinal floras and pharmacopeias. Understanding how and why people select plants for medicine is still a common focus and topic addressed by the interdisciplinary research fields of ethnobotany, anthropology, ethnopharmacology, ethnomedicine, pharmacy, phytochemistry, and pharmacognosy. Here, we scrutinize recently reviewed ethnobotanical theories and hypotheses, which focus on the selection of plants as medicine by putting them into historical, ecological, and pharmacological perspective. We contextualize the availability, versatility, and diversification hypotheses, often presented in association with the inclusion of non-native species or imported herbal drugs into medicinal floras or ethnopharmacopeias. We also discuss the relevance of the concept of utilitarian redundancy and the apparency hypothesis, as well as the appropriateness of various statistical models applied for assessing non-random plant selection. It appears that the concept of utilitarian redundancy has been applied in a too reductionist and uncritical way, while the apparency theory is conceptually inconsistent and contradictive allowing for multiple interpretations. While the availability, versatility, and diversification hypotheses are not contextualized historically, they are used to explain retrospectively deliberate and well-documented human activities and cultural developments. Therefore, considering the cultural history and the pharmacology of plants is essential for the formulation of hypotheses related to the selection of plants as medicine and food. Ecological research questions applied to human-plant relationships should consider the historical impact of human culture as a framework and confounder to be integrated into the analysis.