^ 22 



e. Percent germination: Little difficulty 

 was encountered germinating seed (Sarah 

 Mathews, pers. cornm.)' 



5. Seedling ecology: Not known, although both 

 small and large rosettes were observed. 



6. Survival and mortality: Population sizes were 

 quite large, and most had a good range of 

 plants at each life history stage. 



7. Overall assessment of taxon's reproductive 

 success: Populations of C. lonqistylum are 

 apparently reproductively successful. Data 

 from monitoring transects should provide more 

 information on this subject. 



8. Population ecology of the taxon. 



A. General summary: Total vegetation cover within 

 Cirsium lonqistylum populations ranges from 10 to 

 100 percent. Although it is sometimes found beneath 

 an open forest canopy, it is more often in open 

 meadows. This species has been infested by the 

 weevil Rhinocyllus conicus introduced as a 



I biological control for Carduus nutans. Preliminary 



information on infestation rates are outlined below. 



B. Positive and neutral interactions: None known or 

 observed. 



C. Negative interactions. 



1. Herbivores, predators, pests, parasites and 



diseases: The seed heads of some plants in the 

 Little Belt Mountains have been attacked by a 

 weevil, Rhinocyllus conicus , which was 

 introduced to North America from Europe as a 

 biological control agent for Carduus nutans 

 (Rees 1982, 1987). The weevil was introduced 

 in several locations including Bozeman Montana 

 in the early seventies. Within several years, 

 the weevils had moved out from the original 

 establishment location. Weevil infestation 

 rates, and the likely effect on seed production 

 and population viability are unknown, although 

 preliminary studies have been begun. Dr. 

 Charles Turner (USDA, Albany, California, pers. 

 comm.), a specialist in the fauna of members of 

 the Asteraceae (Sunflower Family) , has recently 

 completed a study of the weevil's impact on a 

 rare thistle native to California. Although 



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