C. GEOGRAPHIC DISTRIBUTION 



1. Species range: Astragalus scaphoides is a narrow endemic, 

 restricted to the foothills of the Bitterroot Mountains and 

 adjoining valleys in Lemhi County, Idaho and across the 

 mountains in southwestern Beaverhead County, Montana 

 (Barneby 1964) . 



2. Distribution in Montana: The species is known only from 

 southwestern Beaverhead County. There are a total of 14 

 occurrences now entered in the Biological Conservation 

 Database from the drainages of Grasshopper, Horse Prairie, 

 and Medicine Lodge creeks and the upper Beaverhead River. 



3. Occurrences in the study area: Prior to 1994, Astragalus 

 scaphoides was known from two BLM sites in the Horse Prairie 

 Creek drainage, one at the southern base of Bachelor 

 Mountain (005), and one around the state school section just 

 to the north of Clark Canyon Reservoir (008). During this 

 project, additional subpopulations were found on Bachelor 

 Mountain and to the northeast of the Clark Canyon school 

 section. Two new populations were located along Rawhide 

 Creek (013) and in the northern foothills of the Tendoy 

 Mountains (Garfield Canyon, 011). Element Occurrence 

 Records (EORs) for each of the populations in the study area 

 and maps showing their precise locations are provided in 

 Appendix C. 



D. HABITAT 



1. Associated vegetation: In Montana, Astragalus scaphoides 

 grows in sagebrush grasslands usually dominated by Artemisia 

 tridentata (big sagebrush) and Elymus spicatus (bluebunch 

 wheatgrass). Other shrub species which are subdominant or 

 in some cases replace big sagebrush in these habitats 

 include Artemisia tripartita , Artemisia nova, and 

 Chrysothamnus nauseosus . Other common or subdominant 

 grasses at the sites include Stipa comata, Oryzopsis 

 hymenoides , Festuca idahoensis , and Poa secunda. The site 

 at Rawhide Creek has a dominant grass component of seeded 

 crested wheatgrass (Agropyron cristatum) . Among the most 

 conspicuous forb associates are other species of milkvetches 

 including Astragalus agrestis , A. adsurgens , A. 

 atropubescens , A. drummundii , and A. lentiginosus . 

 Additional associates are listed in the general site 

 description fields of the individual EORs in Appendix C. 

 Photographic slides showing the habitats of Astragalus 

 scaphoides are attached at the end of this report. 



2. Topography: Barneby (1964) describes the settings of 

 Astragalus scaphoides throughout its range as "open valleys, 

 low hills, (and) canyon benches ... from 3,500-6,000 feet." 



