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DISCUSSION 



This study narrows a gap in the biodiversity picture for the exceptionally diverse Dillon Resource 

 Area. It also helps to close information gaps for little-known species in Montana and builds 

 upon the BLM status recommendations presented in earlier Dillon Resource Area reports for 

 other species. It strengthens the available information-base for making sound resource 

 management decisions as highlighted below by species and by area. 



Astragalus platytropis and Townsendia nuttaUii are relatively common in the Big Hole and 

 Grasshopper study areas, respectively. Although populations are often small for the former and 

 habitat is somewhat restricted for the latter, both species are widespread and have few, if any, 

 apparent threats. The latter is most widespread in the Sage Creek Study Area (Lesica and 

 Vanderhorst 1995). 



Significant new information was collected on two species, Kochia americana and Oryzopsis 

 contracta. Both were virtually unknown in Montana before this study and not documented from 

 BLM lands. Preliminary information indicates that they have been overlooked, are present in 

 substantial numbers, and are subject to limited tlireats. It is not appropriate to consider these 

 species for BLM designation as sensitive, but they are currently being left on the list of Montana 

 Species of Special Concern with a state rank of "SU" (status unknown) while infomiation is 

 being collected to document their status elsewhere in the state. 



The largest known Montana populations of three endemics were documented, shedding light on 

 the habitat requirements and complementary management actions {Astragalus scaphoides, 

 Lesquerella pulchella, and Lomatium attenuatum). The largest known population of one 

 peripheral species was similarly documented {Stephanomeria spinosa). 



New information was collected for several of the species in a setting of human-caused 

 disturbance, helping to reveal natural dispersal patterns, habitat requirements, and tolerance to 

 disturbance (Erigeron linearis, Lesquerella pulchella, and Lomatium attenuatum). 



Additional distribution information was collected on species that had once been considered 

 designated as State Species of Special Concern; several of these remain on the Watch List 

 because of their limited distribution (Arenaria kingii. Astragalus lentiginosus, * Delphinium 

 bicolor ssp. novum, Eriogonum ovalifolium var. nevadense, Gentiana aquatica, * Gilia 

 inconspicua, Mimulus suksdorfii*, Pediocactus simpsonii, Sphaeromeria capitata, * and Stanleya 

 viridiflora). 



The study areas contain a broad array of terrestrial, low elevation sensitive species and sensitive 

 species habitats of southwestern Montana, particularly the Grasshopper Study Area. But all tliree 

 of the study areas contained special features that warrant mention. The Big Hole Study area 

 represents the center of distribution iox Astragalus platytropis in the state, and has select 

 grassland and steppe allotment areas in excellent condition. Most of the fieldwork was 



