19 

 ^ vegetation type or unusual geologic substrate. 



Within the subgenus Habroanthus, P. lemhiensis is 

 one of five closely related species occurring in the 

 Pacific Northwest region; these also include P. 

 cyaneus . P. payettensis . P. pennellianus . and P. 

 speciosus . Of these latter four, only the first two 

 also occur in Montana. Although they are 

 superficially similar, these species are 

 "technically well-marked taxa which occupy 

 distinctive and hardly overlapping geographic areas" 

 (Hitchcock et al. 1959) . The above ecological and 

 systematic observations suggest that a common 

 ancestor may have given rise, through adaptive 

 radiation, to this complex of regional endemics. 

 Alternatively, it has been hypothesized that P. 

 lemhiensis arose via hybridization between P. 

 cyaneus and P. speciosus , followed by segregation 

 and isolation (Keck 1940) . Chromosome counts for 

 all of these species would be useful in evaluating 

 this possibility (Ramstetter 1983); P. speciosus 

 appears to be a diploid species with n = 8, but 

 chromosome counts for the other species have not 

 been published (Clark 1971) . 



t 6. General environment and habitat description. 



A. Concise statement of general environment and 

 habitat: In Montana, P. lemhiensis occurs 

 predominantly on moderate to steep, east- to 

 southwest-facing slopes, often in open soil areas. 

 At some sites, the populations occur partially or 

 wholly on roadbanks. The populations are found on 

 several geologic substrates, including granite and 

 limestone. Associated vegetation types are most 

 often dominated by Artemisia tridentata and 

 bunchgrasses, including Agropyron spicatum and 

 Festuca idahoensis ; P. lemhiensis is also associated 

 with Pinus ponderosa/Purshia tridentata . Pseudotsuga 

 mejTziesii, and Pinus contorta forest types in parts 

 of its range. The populations in Montana occur at 

 elevations from 4,150 to 8,100 feet. 



B. Physical characteristics. 

 1. Climate. 



a. Koppen climate classification: Type Dfb 

 (Canadian climate) , with snowy winters and 

 moderately warm summers (Visher 1954) . 



b. Regional macroclimate: The climate of 

 m southwestern Montana can generally be 



