SPECIES OF SPECIAL CONCERN 



Cirsiiim lonaistylum 



I. SPECIES INFORMATION 

 A. CLASSIFICATION 



1. SCIENTIFIC NAME: Cirsium lonqistylum Moore & 



Frankton 



2. COMMON NAME: long-styled thistle 



3. FAMILY: Asteraceae (=Compositae; Sunflower Family) 



4. GENUS: Cirsium is native to the northern 



hemisphere, with possibly up to 200 species, 50 of 

 which occur in North America (Cronquist 1955) . 

 Thirteen species are found in Montana, two of 

 which are introduced (Dorn 1984) . 



5. SPECIES: Cirsium lonqistylum is part of a group 



described by Cronquist (1955) as being "poorly 

 understood" and "badly in need of a competent 

 reyision." Hybridization is known to occur in the 

 genus, often between seemingly unrelated species 

 (Cronquist 1955) . Due to variation within some 

 populations of leaf and inyolucral characters, the 

 question of hybridization between C, lonqistylum 

 and possibly C. hookerianum arose (see 

 Schassberger 1991, p. 26) . Specimens were 

 collected in 1991 and sent to the late Dr. Arthur 

 Cronquist of the New York Botanical Garden. After 

 examining the specimens, Cronquist felt that "C. 

 lonqistylum was a 'good species', of limited 

 distribution in Montana", and that "it probably 

 hybridizes with C. hookerianum and possibly C. 

 scariosum" (Roe 1992) . Further studies, in 

 particular isozyme and electrophoretic research, 

 need to be done to clarify this problem. 



Cirsium lonqistylum is distinguished from other 

 Montana species by its dilated, lacerate-f ringed 

 tips on the outer inyolucral bracts, although this 

 character is somewhat variable. However this 

 character separates it from C. hookerianum (with 

 long-tapering, arachnoid-villose involucral 

 bracts) and C. scariosum (with occasional inner 

 involucral bracts dilated and fringed at the tip) . 

 Keys to all the Montana species are available in 



