composed of individuals with characters of C. 

 lonqistylum ^ C. hooker ianum . and perhaps 

 other species, as well as intermediate forms. 

 A specimen collected by Lesica (5836, 

 University of Montana herbarium) is an 

 example of an intermediate form. However 

 further evidence will be required to make a 

 judgement as to whether C. longistylum is a 

 "good" species suffering from introgression 

 with a more competitive species, or a product 

 of hybridization. 



G. POPULATION ECOLOGY 



1. BIOLOGICAL INTERACTIONS 



a. COMPETITION: No research has been conducted. 



However field observations indicate that 

 Cirsium longistylum prefers sites where the 

 soil has been disturbed, whether naturally by 

 burrowing animals or unnaturally by machines. 

 This suggests that C. longistylum favors 

 areas of bare soil and full sunlight with 

 little competition. 



b. HERBIVORY: As mentioned above, the seeds of 



Cirsium longistylum are attacked by a non- 

 native weevil, Rhinocyllus conicus . This 

 insect was brought to North America to combat 

 another introduced pest, Carduus nutans . The 

 effect of this biological control agent on 

 Cirsium longistylum is not known. Research 

 begun to study the impact on seed viability 

 and population viability is continuing. 



Most, if not all, of the Cirsium longistylum 

 populations are on Forest Service land leased 

 for cattle grazing. Although this does not 

 appear to be a serious problem, cattle 

 occasionally eat young flowering stalks and 

 centers of rosettes. 



II. ASSESSMENT AND MANAGEMENT RECOMMENDATIONS 



A. THREATS TO CURRENTLY KNOWN POPULATIONS: The only 



verifiable threat to Cirsium longistylum at this time 

 is its limited distribution to three mountain ranges in 

 Montana. However most populations have high numbers of 

 individuals in a variety of size/age classes and appear 

 to be viable. Thus this threat is somewhat alleviated. 

 The threat of seed predation and thus reduced seed 

 production and population viability by the non-native 



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