THE TAXONOMIC SIGNIFICANCE OF ANTHOCHLORS IN THE SUBTRIBE COREOPSIDINAE (COMPOSITAE, HELIANTHEAE)

Anthochlors (chalcones and aurones) are found in a number of plant families including the Compositae. Within this family they were once thought to occur only in the subtribe Coreopsidinae of the tribe Heliantheae. More recent studies show them to occur also in the tribes Cardueae, Eupatorieae, Helineae, Inuleae, and Lactuceae. This has suggested that anthochlors are no longer good taxonomic markers for the Coreopsidinae. A survey of 69 of approximately 210 genera of the Heliantheae shows anthochlors present only in the Coreopsidinae except for Helianthus, Simsia, Tithonia, and Viguiera, closely related genera of the subtribe Helianthinae. Of the 32 genera of the Coreopsidinae recently recognized, 30 were surveyed from available material and all contain anthochlors except Guardiola and Venegasia. The results indicate that, despite some variation, anthochlors are still good taxonomic markers for the Coreopsidinae. This represents the only case within the family in which a particular type of flavonoid is taxonomically diagnostic at the subtribal level. THE WORK of Geissman and co-workers some 25 years ago (e.g., Seikel and Geissman, 1950a; Geissman and Harborne, 1955; Geissman, Harborne and Seikel, 1956; Harborne and Geissman, 1956) dealt primarily with the isolation and structural elucidation of the socalled anthochlor compounds (chalcones and aurones) from members of the genus Coreopsis (Compositae). At about the same time, Shimokoriyama (Shimokoriyama and Hattori, 1953; Shimokoriyama, 1957) was also investigating anthochlors in Coreopsis as well as looking at a species in the closely related genus Cosmos. Both taxa are members of the subtribe Coreopsidinae, tribe Heliantheae, of the Compositae. The compounds were isolated from floral tissues where they are important as yellow pigments. It is now known that anthochlors occur in a number of plant families other than the Compositae (Seikel and Geissman, 1950b; Geissman and Harborne, 1955; Harborne, 1962, 1966; Wong, 1966; Bohm, 1975; Nigam and Saxena, 1975; Adityachaudhury et al., 1976; Gupta, Seshadri and Sood, 1976; Imperato, 1978; Maradufu and Ouma, 1978; and Water1 Received for publication 7 January 1980; revision accepted 28 May 1980. Appreciation is expressed to: David Giannasi, formerly of the New York Botanical Garden, William Grime of the Field Museum of Natural History, Harold Robinson of the Smithsonian Insitution, and B. L. Turner of The University of Texas at Austin, for help in selecting herbarium material from NY, F, US, and TEX, respectively, for the chemical analyses; Marvin Roberts and John La Duke for unpublished data on Megalodonta and Tithonia, respectively; and NSF for financial support under Grants DEB77-21727 to D. J. C. and DEB-75-20819 to T. F. S. man and Pootakahm, 1979), and they have been detected in species of Compositae other than members of the Coreopsidinae (Harborne, 1966, 1977a; Bohm, Saleh and Ornduff, 1974; Harborne and Smith, 1978; see Bohm, 1975 and Harborne, 1977b, for reviews). Anthochlors have been reported from ferns (Star and Mabry, 1971) and from three species of bryophytes (Markham and Porter, 1978). The early chemical studies on chalcones and aurones (Gertz, 1938; Geissman, 1941a, b; Geissman and Heaton, 1943, 1944), completed largely on genera of Coreopsidinae, prompted Cronquist (1955) in his review of the phylogeny and taxonomy of the family to state (p. 486): "Within the Compositae, their very wide distribution in and usual restriction to the Coreopsidinae furnish further evidence of the naturalness of that subtribe. " Because of the more recent chemical studies which show a broader occurrence of anthochlors within the Compositae and in other families (e.g., Bohm, 1975, for a review), in a new overview of the systematics of the family Cronquist (1977) states that (p. 149): "Now it appears that the concentration of numbers in the Coreopsidinae was an artifact of the selection of materials for study. These pigments are well scattered through the Heliantheae, at least, and they occur infrequently in a wide range of other families as well." Despite the fact that chalcones and aurones are now known to be more widely distributed in the plant kingdom than was once thought, they still do appear to be characteristic of the Coreopsidinae. Anthochlors also have been useful for systematic purposes within several