The term ivesioid Potentilleae is here used to refer to species that at one time or another have been placed in the segregate genera Ivesia, Horkelia, Horkeliella, Purpusia, Comarella, and Stellariopsis. This group of species, which represents a biogeographically interesting radiation in western North America, has been a research focus of the senior author using traditional methodology. Although existing treatments have vacillated between recognizing generic segregates vs. sections of Potentilla, the underlying assumption has been that the species are nested within Potentilla s.s., an hypothesis that has recently been given ITS support by T. Erikkson and M. Donoghue. To address further hypotheses, ITS sequence data was obtained and analyzed for a larger suite of ivesioid Potentilleae and potential sister taxa, resulting in support for the hypothesis that the ivesioid Potentilleae represent a monophyletic lineage, which includes P. newberryi but excludes P. basaltica. On-going studies are underway to elucidate relationships within the ivesioids and with potential sister clades.

Key words: Horkelia, ITS sequence, Ivesia, monophyly , Potentilla basaltica, Potentilla newberryi