Bi-modal altitudinal distributions are relatively uncommon in plant species; if a species occurs at sea level to alpine altitudes, it often occurs at points in-between. Not so with Saussurea nuda, according to the Flora of North America.
Dwarf saw-wort occurs only within two elevational ranges: 0-100m (sea level to 300 ft.) and 2000-2800m (6500-9000 ft.). For a time, the high elevation plants were recognized as a distinct species, Saussurea densa. The Swedish botanist, Eric Hultén and the British Columbian botanist George W. Douglas both concluded that Saussurea densa were part of Saussurea nuda in the broad sense, though worthy of being distinguished; Hultén designated it a variety, while Douglas suggested a subspecies. The plant in today’s photo, from the southeastern British Columbia Rockies on Mount Gass, is still recognized as Saussurea nuda subsp. densa in several BC floristic treatments. However, the treatment in the Flora of North America rejects designating any taxon status below species at all, arguing:
North American populations of Saussurea nuda occur in two distinctly different sets of habitats. Plants from coastal Alaska have been recognized as var. nuda and dwarfed alpine plants from the northern Rockies as var. densa. According to E. Hultén, the only differences between var. densa and var. nuda are the “more densely denticulated leaves and very congested inflorescences” of the former. Notwithstanding the very different habitats, some coastal Alaskan specimens are indistinguishable from the alpine forms.
Saussurea nuda is native to Montana, Alberta, British Columbia, Alaska and Far East Russia. The genus contains approximately 300 species, with a centre of diversity in the Himalayas. The group has two common names, saw-wort and snow lotus. Snow lotus is more typically used for high altitude species in the Himalayas such as Saussurea involucrata (scroll down for photos).