Biosynthetic and Chemosystematic Aspects of the Euphorbiaceae and Thymelaeaceae

Adolf and Hecker provide a hypothetical discussion of likely biosynthetic relationships between the various diterpenoid compounds of the Euphorbiaceae and Thymelaeaceae. Notwithstanding the dearth of biosynthetic evidence, there is perhaps sufficient phytochemical information available to enable a genealogical argument to be developed regarding the taxonomic positions of the families Euphorbiaceae and Thymelaeaceae. Hutchinson provides a diagrammatic overview of the presumed evolutionary relationships between the Euphorbiales and Thymelaeales showing the polyphyletic nature of the Euphorbiales. It should be noted that Hutchinson perceives the Euphorbiales as comprising the Euphorbiaceae only, with the Thymelaeales comprising six families. It is evident that there is much disagreement between taxonomists as to the affinities of the Euphorbiaceae and Thymelaeaceae, and the evolutionary relationships between the various families and orders. Reference to the work of Mitchell and Rook provides literature references to the occurrence of skin irritancy in certain members of other families thought to be related to the Euphorbiaceae and Thymelaeaceae.