Flora of North America species comparison

Subspecies 7 (1 in the flora).

The status of Potentilla supina in North America is open to question, given the otherwise Eurasian and northern African distribution of the species and ease of transport by migratory waterfowl. Although North American material has commonly been treated as a distinct species (P. paradoxa), E. Hultén and M. Fries (1986) went so far as to consider P. supina introduced in North America. The use of subspecies within a broadly defined P. supina follows J. Soják (1987, 1993) and is also adopted by A. Kurtto et al. (in J. Jalas et al. 1972+, vol. 13).

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Potentilla nana has most often been considered a race of P. hyparctica or as the priority name for P. hyparctica. As now defined, P. nana occurs in an arc across southern Alaska, from the Aleutian and Pribilof islands to the Alaskan panhandle and adjacent British Columbia. T. Wolf (1908) treated it as a dwarf form of P. fragiformis; J. Soják (1996) interpreted P. nana as a hybrid species originating from cross(es) between P. fragiformis and P. hyparctica. Although the hybrid hypothesis has morphologic support, P. nana has a unique combination of morphologic features and has a distinct range from both P. fragiformis and P. hyparctica. The species are also ecologically segregated: P. nana is a coastal heath and gravel slope species, like P. hyparctica; P. fragiformis is strictly maritime coastal.

(Discussion copyrighted by Flora of North America; reprinted with permission.)