F. POPULATION DEMOGRAPHY, BIOLOGY AND SPECIATION 



1. PHENOLOGY: Flowering begins near the end of June, 



peaks in July and extends into August. Flowering 

 sequence occurs basipetally in C. longistyluin , 

 with the lowermost flowering heads developing 

 last. Seeds mature in August and September, and 

 would appear to be primarily wind dispersed. 

 Seeds have been germinated successfully without 

 cold stratification or scarification, and 

 therefore may germinate in the fall. (Adapted from 

 Schassberger 1991) . 



2. POPULATION SIZE AND CONDITION: Most populations of 



Cirsium longistylum are quite large (hundreds to 

 tens of thousands of individuals) . However these 

 populations are often a mix of C. longistvlum , C. 

 hooker ianum , and various morphologically 

 intermediate combinations so the exact number of 

 individuals of C. longistvlum is not known. 



The population in the Elkhorn Mountains was a mix 

 of both species with only one plant among 

 approximately one hundred being identifiable as 

 Cirsium longistvlum . 



The populations in the Big Belt Mountains varied 

 in size from 7 to upwards of 5000 individuals (see 

 Appendix 5) . Although not noted at every site, 

 hybridization with Cirsium hookerianum was 

 probably occurring. The presence of weevils was 

 noted at two sites (EOR#s 022 and 023) . 



3. REPRODUCTIVE BIOLOGY 



a. TYPE OF REPRODUCTION: Cirsium longistvlum is 

 said to reproduce both asexually by biennial 

 offsets from a perennial rhizome (Moore and 

 Frankton 1963), and sexually by seed. No 

 evidence of rhizomes were found when it was 

 collected on the Helena National Forest. 

 Populations contain a range life history 

 stages, from single whorl rosettes through 

 larger multiple whorl rosettes to flowering 

 and fruiting individuals. Whether the 

 species is a perennial or a strict biennial 

 is not yet known. Small (single whorl) to 

 large (multiple whorl) rosettes are observed 

 in populations as well as flowering plants, 

 perhaps representing a three growth season to 

 flowering stage. Demographic monitoring 

 studies begun in 1990 will help determine 



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