the life history of the species (adapted from 

 Schassberger 1991) . 



b. POLLINATION BIOLOGY: Cirsium lonqistylum is 



probably primarily insect pollinated. 

 Bumblebees (Bombus sp.) as well as other bee 

 genera have been observed to visit the 

 flowering heads, and may be the main 

 pollinators. It is not known whether self- 

 pollination occurs. 



c. SEED DISPERSAL AND BIOLOGY: Cirsium 



lonqistylum can produce numerous seeds. The 

 presence of a lengthy, fluffy pappus suggests 

 that the seeds are wind-dispersed. The seeds 

 are subject to predation by a non-native 

 weevil, Rhinocyllus conicus, which was 

 brought to North America to control the 

 introduced weed, Carduus nutans (Schassberger 

 1991) . Studies are continuing on the effect 

 of the weevil on C. lonqistylum seed 

 production. In 1992 most seeds appeared to 

 have aborted (i.e., blackened and not filled 

 out) . The cause is not known. 



d. PHYLOGENY AND SPECIATION: Cirsium lonqistylum 



was first recognized as a distinct species by 

 Moore and Frankton in 1963. They felt that 

 due to the limited distribution of the 

 species and the considerable variation in 

 habit and head arrangement, C. lonqistylum 

 might be a hybrid (Moore and Frankton 1963) . 

 However pollen was 95% normal, which does not 

 support the hybrid thesis but also does not 

 rule it out (Moore and Frankton 1963) . The 

 lacerate outer involucral bract character is 

 unique for thistles in Montana. Moore and 

 Frankton (1963) stated that this unusual 

 character might be the result of a hybrid 

 combination of genes. Although Moore and 

 Frankton do not explicitly name the parents, 

 they do mention that C. hookerianum and C. 

 kelseyi (= C. scariosum according to 

 Hitchcock and Cronquist, 1973) are most 

 similar in general appearance and occur in 

 the same region. 



A morphological analysis of 15 populations of 

 Cirsium lonqistylum gathered from the Little 

 Belt, Big Belt, and Elkhorn Mountains this 

 summer is still in progress. Initial 

 findings indicate that all populations were 



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