A narrow endemic of southwestern Utah, Erigeron flagellaris A. Gray var. trilobatus Maguire ex Cronq., is given specific status as Erigeron proselyticus Nesom. It is closely related to two other rare endemics of the Zion National Park area, Erigeron religiosus Cronq. and Erigeron sionis Cronq., but it does not share a similarly close relationship with typical E. flagellaris. Erigeron proselyticus in diploid; E. sionis is tetraploid and probably agamospermic; three diploid populations and several triploid populations of E. religiosus are known, including a population of triploids from the site of a paratype collection of this species. Variation in these triploids suggests the possibility of hybridization with Erigeron divergens Torr. & Gray, or with an unknown species no longer occurring sympatrically with E. religiosus,.