New Combinations and New Genera in the North American Tarweeds (Compositae-Madiinae)

Abstract

New combinations and new genera for species in Hemizonia DC., Molina, and Raillardiopsis Rydberg allow for a revised, practical taxonomy of Madiinae that better reflects phylogenetic relationships. Reinstatement of Anisocarpus Nuttall, Centromadia Greene, Deinandra Greene, and Hemizonella A. Gray, abandonment of Raillardiopsis Rydberg, and recognition of four new genera (Carlquistia, Harmonia, Jensia, Kyhosia) for tarweed lineages without available generic names result from changes in circumscription based on monophyletic groups. Results of phylogenetic, biosystematic, and cytogenetic studies in Madiinae (Kyhos et al., 1990; Baldwin et al., 1991; Baldwin, 1992, 1993, 1996, unpublished; Carr et al., 1996) indicate that Hemizonia DC. sensu Keck (1959), Molina sensu Keck (1959), and Raillardiopsis Rydberg are not monophyletic. Hemizonia sensu Keck (1959) comprises a minimum of three monophyletic groups that correspond to section Centromadia (Greene) D. D. Keck, section Hemizonia, and section Madiomeris Nuttall sensu Tanowitz (1982) plus the informal Fruticosae or Zonamra (cf. Clausen, 1951; Keck, 1959). sensu Keck (1959), Raillardiopsis, and the monophyletic Hawaiian silversword alliance (Argyroxiphium DC., Dubautia Gaudichaud-Beauprd, Wilkesia A. Gray; see Carr, 1985) constitute a clade lacking a formal name (the Madia lineage in Baldwin, 1996) that is extremely heterogeneous and difficult to diagnose morphologically. The Hawaiian group comprises trees, shrubs, subshrubs, large rosette plants, mat plants, cushion plants, and vines that are strikingly divergent in morphological and ecological characteristics from the primarily Californian herbs in sensu Keck (1959) and Raillardiopsis (see Carr, 1985; Baldwin & Robichaux, 1995; Baldwin, 1997). In addition to the distinctive Hawaiian lineage, a minimum of seven monophyletic groups can be reliably diagnosed from morphological and molecular data within the clade comprising sensu Keck (1959), Raillardiopsis, and the silversword alliance. Recognition at the generic level of each of the three lineages in Hemizonia sensu Keck (1959) and each of the seven lineages in the paraphyletic group comprising sensu Keck (1959) plus Raillardiopsis in the traditional (only) sense results in a practical taxonomy that conforms to the criterion of monophyly (= holophyly) of taxa. The revision of sensu Keck (1959) plus Raillardiopsis (hereafter, MADRAIL) also allows for continued generic distinction of the unusual Hawaiian species in the silversword alliance without maintaining non-monophyletic California tarweed genera. I realize that additional nomenclatural changes in the silversword alliance are necessary to achieve a taxonomy of the Hawaiian species that includes only monophyletic genera. The new combinations herein focus only on genera relevant to treatments in preparation for the Flora of North America North of Mexico.