Abstract/Summary

Ethnobotanical knowledge of plants’ medicinal use could make a contribution to bioprospecting by identifying plants to target for drug discovery. In recent years, methods to investigate the medicinal uses of flowering plants using a phylogenetic framework have been developed. Drugs derived from higher plants are prevalent, and ferns are relatively neglected. Thus, this thesis investigates the evolutionary patterns amongst fern species that are used medicinally using phylogenetic tools at a range of taxonomic and spatial scales, from global to regional scales, for the first time. Dense sampling at species levels may be critical for comparative studies, thus an updated fern megaphylogeny focusing on four gene regions, rbcL, rps4, atpA and atpB was reconstructed. This large-scale phylogeny comprises more than 3500 fern species in 273 genera and 47 families, covering over a quarter of extant global fern species. To evaluate the medicinal importance of ferns, a database based on a comprehensive review of records published in books, journals or in online sources including databases was assembled. The use database comprised 3220 use-reports for 442 species, and showed that approximately 5% of total estimated extant fern species have a documented therapeutic use, but only 189 species have become the focus of screening concerning their bioactivity properties. Using a comprehensive phylogenetic tree and medicinal data from the database, species used in traditional medicine were shown to be significantly dispersed across the fern phylogeny, contrary to previous findings in many similar studies of flowering plants. Whatever the hierarchical level or spatial scale investigated, the results consistently found evidence of phylogenetic overdispersion of medicinal use, suggesting more exploration of medicinal uses in a phylogenetic context is required before the generality of this approach is globally accepted. Finally, safety and toxicity of ferns that are used as medicine and food were also explored, since fern consumption can pose a serious health risk. The distributions of toxic compounds and arsenic hyperaccumulation in ferns were investigated using taxonomic and phylogenetic approaches in order to access the risk to consumers. Overall, assessment of toxicity in ferns is still limited and awareness needs to be raised about the health risks associated with the use of ferns.