STEBBINSOSERIS

Stebbinsoseris comprises two allotetraploid species derived from hybrids between Microseris and Uropappus. The justification for raising these species to generic rank was given in R. K. Jansen et al. (1991b), where molecular data were presented supporting the separation of Uropappus from Microseris. Stebbinsoseris and Uropappus were ranked as sections of Microseris in earlier taxonomic treatments (K. L. Chambers 1955, 1960). Because of its hybrid origin, Stebbinsoseris is intermediate in critical taxonomic traits of habit, involucre, and fruits (C. Irmler et al. 1982), and it is separated from its parental taxa by rather minor differences. Chloroplast DNA studies show that Microseris douglasii and M. bigelovii were the maternal parents of the tetraploid hybrids (R. S. Wallace and R. K. Jansen 1990). That Uropappus lindleyi was the staminate parent of those crosses is confirmed by nuclear rDNA evidence reported by Wallace and Jansen (1995).