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25 



transects ranged from 1.4 to 3.5 (Shelly 

 1990b) . 



5. Successional phenomena: As discussed above, P. 

 lemhiensis appears to have an ecological 

 preference for more open, often unstable, 

 microhabitats; these include rock outcrop areas 

 and steep rocky slopes with some natural soil 

 slippage. This adaptation is further evidenced 

 by situations where plants have colonized open 

 roadbanks (i.e., Argenta (001), Trail Creek 

 (002), Polaris (032)). The species is never 

 abundant, and is likely to be ephemeral, in 

 these disturbed situations. All known sites 

 are in open habitats, and the species would 

 probably be intolerant of canopy closure. 



6. Dependence on dynamic aspects of biotic 

 associations and ecosystem features: Unknown. 



7. Other endangered, threatened, rare, or 

 vulnerable species occurring in habitat (s) of 

 this taxon: None known in Montana. 



7. Population biology of the taxon. 



A. General summary: In Montana, populations range in 

 size from single, isolated plants to 1,845 or more 

 individuals; these populations contain from one to 

 13 subpopulations. During the period 1986-1989, 

 drastic declines have been noted in three 

 populations. Penstemon lemhiensis does have some 

 capacity to colonize disturbed areas, and is 

 occasionally frequent in such situations, but the 

 plants in such areas are probably ephemeral. 

 Studies of pollination biology revealed a possibly 

 close relationship with a species of vespid wasp 



( Pseudomasar is vespoides ) , and Penstemon lemhiensis 

 appears to be an obligate out-crosser (Ramstetter 

 1983) . Demographic monitoring transects established 

 in 1989 revealed the presence of relatively few 

 seedlings, but the timing of seed germination and 

 establishment is unknown. 



B. Demography. 



1. Known populations: Thirty-five recently 



documented populations are known in Montana. 

 The average population size is approximately 

 128. The total number of plants observed in 

 Montana to date is approximately 4,4 20-4,525. 

 The populations in Montana are sparsely 

 scattered over an area of approximately 3,500 



