INTRODUCTION 



The Pioneer Mountains dominate the north-central portion of 

 Beaverhead County, Montana. The mountains are a vast piece of 

 Idaho batholith granite, which broke off and slid east into 

 Montana, crumpling sedimentary rocks to the east. As a result, 

 vast quantities of granitic intrusions penetrate folded 

 sedimentary rocks along the eastern edge of the range. The 

 Wisdom Valley to the west is thought to be a result of the 

 movement of this very large piece of granite (Alt and Hyndman 

 1986). To the east lies the Dillon Valley (5,200 ft in 

 elevation) from which the Pioneer Mountains rise, up to a maximum 

 elevation of 10,568 ft. Because this range lies to the east of 

 the continental divide, it is dominated by a dry continental 

 climate, and the area receives the highest amounts of 

 precipitation during May through October. Spring and fall bring 

 rain or snow, while the summer months are dominated by convective 

 rain storms. Due to factors of geology and past glaciations, 

 topography, and climate, the area supports a diverse vegetation. 

 Great Basin, southern Rocky Mountain and northern boreal plant 

 species are all found in the Pioneer Mountains. Communities 

 range from wetlands to sagebrush grasslands, montane and 

 subalpine forests, to alpine slopes. Only a small portion of the 

 range has been botanized to any degree, and many of the records 

 for plant species of special concern are old and unverified. 



This study was undertaken to try and relocate and verify 

 sensitive species that occur in the Pioneer Mountains. This 

 report contains information on a rare plant inventory conducted 

 8-13 and 29-31 July 1990 in portions of the Pioneer Mountains. 

 These surveys emphasize the verification of old records for the 

 species involved. Reports describe the status of populations of 

 Haplopappus macronema var. macronema. and Mimulus primuloides 

 that were relocated during the survey and a newly located 

 population of Cirsium subniveum . 



METHODS 



On the basis of existing floristic information, a list of 

 sensitive plant species that were known or had potential to occur 

 in the Pioneer Mountains was prepared. Species included were: 



Known : 



Claytonia lanceolata var. f lava (yellow springbeauty) 



Haplopappus macronema var. macronema (discoid 



goldenweed) 



Mimulus primuloides (primrose monkey flower) 



Saxifraqa tempestiva (storm saxifrage) 



Selaqinella watsonii (Watson's selaginella) 



