Abstract
Field studies and herbarium analyses of populations of Potentilla L. sect. Graciles (Rydb.) A. Nels. with atypical petiole vestiture result in the description of Potentilla gracilis Douglas ex Hook. var. owyheensis as a new variety, differing from var. elmeri and var. flabelliformis in having cottony-tomentose vestiture on the petioles instead of appressed to spreading straight hairs. The new variety grows in mid-montane meadows from the Owyhee Mountains in southwestern Idaho to the Ochoco Mountains in northeastern Oregon. It is conceivably of hybrid origin, with Potentilla breweri S. Watson providing the petiole vestiture that is otherwise unknown in Potentilla sect. Graciles. The study also resulted in the improved understanding of Potentilla bruceae Rydb. as a relatively coherent taxon centered in meadows around Lake Tahoe, California. As a result, Potentilla bruceae, Potentilla drummondii Lehm., and Potentilla breweri are recognized as distinct species, with Potentilla subvillosa Rydb. and Potentilla anomalofolia M. Peck as synonyms of Potentilla bruceae. Potentilla versicolor Rydb. is also recognized as a distinct species related to P. breweri but differing in having straight silky hairs rather than cottony tomentum.
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