SUMMARY 



Cirsium longistylum is a perennial thistle that is 

 endemic to central Montana primarily in the Little Belt 

 Mountains. It is currently known from areas on the 

 Lewis and Clark National Forest and on private lands in 

 the Little Belt Mountains, and from one site on the 

 Helena National Forest, Big Belt Mountains. Cirsium 

 longistylum is currently on the Watch List of sensitive 

 species for Region 1 of the U.S. Forest Service, and is 

 categorized by the U.S. Fish and Wildlife Service as 

 C2. In the 1991 list of Plant Species of Special 

 Concern, Cirsium longistylum will be ranked by the 

 Montana Natural Heritage Program as an S3 species; 

 "rare in Montana (21+ occurrences). 11 Although there 

 are only 20 locations currently mapped, many 

 populations contain tens of thousands of individuals, 

 and the species is nearly ubiquitous within moist to 

 wet meadows in the Little Belt Mountains. 



Cirsium longistylum occurs frequently in disturbed 

 roadsides, meadows and openings in forests as well as 

 undisturbed sites in native grasslands and grassy 

 openings in forests. It occurs over a wide altitudinal 

 range of about 4700-8000 feet. Cirsium longistylum 

 reproduces both asexually from rhizomes and sexually by 

 seeds. A weevil, Rhinocyllus conicus, which was 

 introduced as a biological control for musk thistle 

 (Carduus nutans ) , has attacked the seed heads of many 

 C. longistylum plants. Although, the effect on seed 

 production and population viability is not known, this 

 insect could pose a threat to C. longistylum in the 

 long term, and its impact should be evaluated. 



Morphological variation in some local populations has 

 led to questions about possible hybridization with 

 another Cirsium species and about the systematic status 

 of C. longistylum itself. Hybridization could also be 

 a threat to the viability of C. longistylum 

 populations. No threats are currently known from 

 timber harvestinq or domestic qrazinq. 



Permanent plots were set up at three sites to study 

 life history characteristics of C. longistylum . 

 Density of C. longistylum varied from 0.24 plants/m 2 at 

 Russian Creek to 2 . 1 plants/m 2 at Neihart. The 

 percentaqe of plants in flower was hiqhest at Russian 

 Creek (35%) , and was lower at Kinqs Hill and Neihart 

 (28% and 17%, respectively). However the reverse trend 

 was observed at the rosette staqe where qreater 



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