3. Diagnostic characters: T. parviflorum is very similar to 

 the more common native T. montanum (T . fendleri) , but differs 

 by having shorter sepals (2-3 mm long in T. montanum) , petals 

 (44-6 mm long in T. montanum) , and styles (1-3 mm long in T. 

 montanum). Thlaspi arvense , also in Montana, is a very common 

 annual weed, with large notched or hear-shaped fruits with 

 wide wings (adapted from Hitchcock et al 1964 and Dorn 1984) . 



B. GEOGRAPHIC DISTRIBUTION 



1. Species range: "...central Idaho to northwest Wyoming and 

 southwest Wyoming" (Hitchcock and Cronquist 1973). 



2. Montana distribution: Eight previous records have been 

 documented from Beaverhead, Carbon, Madison, and Silver Bow 

 Counties . 



3. Occurrences in the study area: One population was found 

 about two miles south of the confluence of Meadow and Big 

 Sheep Creeks, in the southern part of the area. 



C. HABITAT 



The population grows in moist bottomland on an alluvial 

 terrace. Vegetation is dominated by Artemisia cana, Juncus 

 balticus, and Poa nevadensis . Other associates are Antennaria 

 microphylla, Penstemon procerus , and Polygonum bistoides . 

 There is evidence of past grazing, and weeds occupy some of 

 the area. The soil is a loam. 



D. POPULATION BIOLOGY 



There are at least four subpopulations which together consist 

 of over 300 estimated plants and cover between on\e and ten 

 acres. The fruit was mature and dispersing in early July. 

 Plants were beyond the stage when they could be easily 

 surveyed. 



E. MANAGEMENT CONSIDERATIONS 



T. parviflorum is a regional endemic now known from nine sites 

 in Montana. Most populations are small even though habitat is 

 abundant. The plants are small and inconspicuous, flower 

 early, and are ephemeral. consequently, it may be more 

 abundant than is currently known. Many sites are grazed by 

 livestock; however, this small, short-lived perennial may 

 benefit from moderate disturbance episodes. It is not 

 recommended for further ELM consideration, although it should 

 be retained on the list of plants tracked by the Montana 

 Natural Heritage Program. 



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