Results of phylogenetic analyses of nuclear ribosomal DNA sequences from Heliantheae s.l. (sensu lato) lead us to conclude that Pelucha should be placed taxonomically in Helenieae s.s. (sensu stricto) rather than in Plucheeae or Inuleae s.l. The sister-group relationship between Pelucha and a clade comprising Psathyrotes and Trichoptilium inferred from nuclear ribosomal DNA trees is in accord with morphological characteristics shared by the three genera and with their common restriction to desert environments of western North America. The shrubby habit of Pelucha is unusual in the otherwise mostly-herbaceous Helenieae s.s. and is conceivably the result of evolution on islands in the Gulf of California. In a revised subtribal classification of Helenieae s.s., two new subtribes are erected: Psathyrotinae, for the group comprising Pelucha, Psathyrotes, and Trichoptilium, and Plateileminae, for Plateilema. Gaillardiinae is delimited to comprise Balduina, Gaillardia, and Helenium s.s., Marshalliinae is retained for Marshallia, and Riddelliinae is reinstated for Amblyolepis, Baileya, Hymenoxys sensu Bierner, Psilostrophe, and Tetraneuris.

Communicating Editor: Jerrold I. Davis