THE DISTRIBUTION OF ANTHOCHLOR FLORAL PIGMENTS IN NORTH AMERICAN COREOPSIS (COMPOSITAE): TAXONOMIC AND PHYLETIC INTERPRETATIONS

Anthochlors (chalcones and aurones) occur in floral tissues of all members of North American Coreopsis . The genus in North America consists of 46 species distributed in 11 sections, and a total of five chalcone aglycones are found in it. The chalcone butein occurs in all sections, and is the only anthochlor constituent in the closely related woody Mexican sections Electra and Anathysana . These two sections are viewed as primitive. The morphologically distinct but putatively unspecialized woody Mexican section Pseudo‐Agarista sequesters both okanin and butein; the same two anthochlors also characterize two additional sections of herbaceous perennials, Silphidium and Tuckermannia . Sections Euleptosyne and Pugiopappus , comprised of annuals restricted primarily to California, exhibit the rare chalcone stillopsidin in addition to butein and okanin. The remaining four sections, Palmatae, Coreopsis, Calliopsis and Eublepharis are among the more specialized in North America, and are sometimes considered to represent a distinct phyletic line or two related lines. All or some of the members of these sections sequester the very rare chalcone lanceolatin in floral tissues in addition to okanin. Butein is also present in some or all species in each section, and isoliquiritigenin occurs rarely in two sections. Those sections considered more specialized have additional anthochlors relative to primitive sections, and any compound found in a more primitive section also occurs in a more advanced one. Thus, the trend in floral anthochlors in North American Coreopsis is toward increased number of compounds rather than reduction.