SUMMARY 



Cirsium lonqistylum is a perennial thistle that is endemic to 

 central Montana. It is primarily known from Little Belt 

 Mountains, where it is nearly ubiquitous within mesic to moist 

 meadow and stream terrace sites. A summary of the status of this 

 species can be found in Schassberger and Achuff (1991) and 

 Schassberger (1991) . 



In 1991, Cirsium longistylum was removed from the Watch List of 

 sensitive species for Region 1 of the U.S. Forest Service due to 

 abundance. However, because it is a state endemic known from a 

 limited area (albeit common in that area) , and may be threatened 

 by a weevil introduced as a biological control agent (used in an 

 effort to limit the spread of the introduced Carduus nutans ) , it 

 continues to be categorized by the U.S. Fish and Wildlife Service 

 as C2 (U.S. Department of the Interior 1990). Cirsium 

 lonqistylum is also ranked by the Montana Natural Heritage 

 Program (Achuff 1991) as an S3 species; "rare in Montana (21+ 

 occurrences)." 



Morphological variation in some populations has led to questions 

 about possible hybridization with other Cirsium species, and 

 about the systematic status of C. lonqistylum . Numerous 

 collections were made during the 1991 field season, and sent to 

 Dr. A. Cronquist (Botanist, New York Botanical Garden) for 

 review. Based on this material. Dr. Cronquist (1992) stated that 

 he now felt that "C. lonqistylum was a "good" species of limited 

 distribution in Montana." He also felt that "it probably 

 hybridizes with C. hookerianum and possibly C. scariosum Nutt.", 

 and that "hybrids were best identified in the field." Dr. 

 Cronquist annotated the specimens from the population at Neihart 

 as C. hookerianum Nutt., and they will be considered as such in 

 the demographic studies. In light of the results of the 

 morphological overview, it would be appropriate to use techniques 

 of electrophoresis to support the hybridization hypotheses. 



Permanent plots were set up at three sites (Russian Creek, Kings 

 Hill, Neihart) in 1990 to study life history characteristics of 

 C. lonqistvlum . As stated above, the population at Neihart will 

 now be considered as C. hookerianum . Changes in population 

 numbers from 1990 to 1991 within study plots were found to be a 

 result of: loss of plants which had flowered in the previous 

 year, loss of plants at the rosette stage, and recruitment rates. 

 Over this short period, population sizes and number of plants 

 flowering fluctuated, but only further study will determine if 

 this is normal for the species. 



At Kings Hill in 1991, disturbance of the soil by rodents 

 eliminated previously established rosettes, but appeared to aid 

 in the germination of seeds as evidenced by the numerous 

 seedlings present. At Neihart, many plants (31%) were grazed, 

 either lightly or heavily. How grazing ultimately affects the 

 ability of these rosettes to reach maturity will be revealed 

 through continued monitoring. 



