18 



4. Locations not yet investigated believed likely 

 to support additional natural populations: The 

 following areas in Beaverhead County, Montana 

 may support populations: Big Hole Divide, 

 south of Big Hole Pass; west Pioneer Mountains, 

 including the upper Grasshopper Creek and Wise 

 River drainages; east slope of the Beaverhead 

 Mountains, between Jackson and Wisdom. 



In southern Ravalli County, potential habitat 

 exists at low to mid-elevations in most major 

 drainages; a recent report from the Woods Creek 

 drainage (036; tributary of the West Fork 

 Bitterroot River) substantiates the need for 

 additional surveys in this region. However, P. 

 lemhiensis may in fact be relatively rare here; 

 the four Ravalli County populations located 

 during 1989 surveys were widely scattered, and 

 three of these were very small in size. 



5. Reports having ambiguous or incomplete locality 

 information: None known. 



6. Locations known or suspected to be erroneous 

 reports: None known. 



C. Biogeographical and phylogenetic history: The 



diversity of habitat types occupied by P. lemhiensis 

 is fairly wide, which is unique considering the 

 narrow geographic range of the species. In Montana, 

 the known populations occur at elevations from 4,150 

 feet along the East Fork of the Bitterroot River, to 

 8,100 feet in the northeastern Pioneer Mountains. 

 As a result, the plant communities with which P. 

 lemhiensis is associated are highly varied. At the 

 lowest elevations in Ravalli County it occurs in dry 

 foothills habitats, and is associated with Pinus 

 ponderosa and Purshia tridentata . Most of the known 

 sites in Beaverhead County, however, are associated 

 with Artemisia tridentata and various bunchgrasses, 

 especially Agropyron spicatum and Festuca 

 idahoensis ; the majority of these populations are 

 very close to, and often extend into, the lower 

 edges of the Pseudotsuga menziesii forest zone. The 

 sites at the highest known elevations in Montana, 

 near Vipond Park in the northeastern Pioneer 

 Mountains, are actually associated with Pinus 

 contorta , and occur in moist forb meadows and on 

 open slopes. This wide ecological tolerance, in a 

 species with a narrow geographic distribution, 

 suggests that the range of P. lemhiensis may be most 

 closely related to its evolutionary history, since 

 it is apparently not strictly confined to a single 



