THE PHYLOGENETIC SIGNIFICANCE OF FLAVONOIDS IN CRAMBE L (CRUCIFERAE)

A total of 21 flavonoid compounds were detected in 14 spp. of Crambe. In general, both sections of the genus and the species can be distinguished easily by their flavonoid patterns. The members of Crambe sections Crambe and Dendrocrambe seem to be the most primitive with their perennial or rhizocarpous habit. They show a diversity of flavonol glycosides, derived from either kaempferol or quercetin. The presumed presence of proanthocyanidins confers an additional primitive character to Crambe section Dendrocrambe. In contrast, members of Crambe section Leptocrambe show a relatively poor pattern where the quercetin glycosides have disappeared. In the case of C. hispanica and C. abyssinica flavonols are completely absent while 2 flavones, luteolin and apigenin appear in glycosidic form: these are probably the most evolved Crambe species and exhibit an annual habit. A dendrogram exclusively based on data of the presence or absence of flavonoids was constructed. It is similar to the one that could have been expected from use of morphological data alone, but it does provide some hints on the possible phylogenetic relationships between the species. Flavonoid evidence also supports the hypothesis on an east-west Mediterranean disjunction within the genus.