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Flavonoids and taxonomy of the Limnanthaceae Parker, William Harrison


The Limnanthaceae is a small family of North American annual herbs with uncertain relationships. It is generally recognized to consist of two genera, Limnanthes and Floerkea, together containing 10 species with 13 varieties and subspecies. To help clarify relationships within this family, a comparative flavonoid investigation was undertaken. All taxa were compared on the basis of flavonoids occurring in all tissues, and most Limnanthes taxa were additionally compared on the basis of flavonoids occurring in the petals and the ultraviolet reflectance characteristics of their flowers. A total of hd flavonol glycosides were encountered. Of these, 35 were identified as derivatives of six flavonol aglycone types: syringetin, isorhamnetin, kaempferol, laricytrin (myricetin 3'-methyl ether), quereetin and myricetin, all glycosylated with combinations of glucose and rhamnose. The flavonoid data were analyzed by three numerical taxonomic techniques: clustering by the weighted pair group method, Principal Components Analysis, and Varimax Factor Analysis with rotation. Duplicate comparisons were made according to type of tissue analyzed and concentrations of flavonoids considered. Classifications based on petal flavonoids occurring in relatively higher concentrations were found to reflect most clearly natural relationships in Limnanthes. The ultraviolet reflectance characteristics of flowers were found to distinguish one supra-specific group of Limnanthes taxa from the remainder of the genus. The adaptive significance of ultraviolet patterning is discussed, together with its implications concerning flavonoid compositions. The method and validity of using flavonoids as taxonomic characters is also discussed. Flavonoid and ultraviolet reflectance characteristics are integrated with all other taxonomi-cally significant information known for the Limnanthaceae, and proposals for taxonomic revision are made. A synopsis of the family is presented which recognizes one genus, Floerkea, containing 15 species with 5 varieties.

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