exotics. The Charleys Gulch population should be most affected by 

 disturbances that destroy adults, such as trampling or herbicide application. 

 The differences in life history traits are at least partly controlled by the 

 frequency of bolting and axillary flowering, and the fact that both types of 

 flowering occurred in all populations suggests that there is probably ample 

 variation, genetic or plastic, to compensate for any changes that may occur if 

 they are not too drastic and do not occur too quickly. 



Management Considerations 

 Results of our studies suggest that Arabis f ecunda populations at Lime 

 Gulch and Vipond Park are stable or growing. Population growth at these sites 

 depends heavily on recruitment from seed, a life history stage that is 

 probably buffered by the presence of a long-term seed bank. Weed infestations 

 could pose a serious problem as they can reduce recruitment of A_^ fecunda 

 (Lesica and Shelly submitted) . Furthermore, weed infestations are most 

 frequent in the mesic grassland and xeric forest zones in western Montana 

 (Forcella and Harvey 1983), the same habitats where A_^ fecunda is most common. 

 At this time, there are no serious weed infestations near any known 

 populations in Beaverhead or Silver Bow counties. Nonetheless, encroachment 

 by exotics is a very real potential problem. Populations of A^ fecunda should 

 be regularly monitored for exotics, and roads and other disturbances that 

 promote weed infestations should be minimized in these areas. 



Populations of Arabis fecunda at Charleys Gulch and Birch Creek (Lesica 

 and Shelly 1993) may be declining. Results of our studies indicate that the 

 Charleys Gulch population will be most sensitive to declines in the survival 

 of mature plants. Centaurea maculosa is present at all Ravalli County sites, 

 and this aggressive exotic does have a negative effect on A_^ fecunda 

 population growth (Lesica and Shelly, submitted) . However, the main negative 

 effect of C^ maculosa on A^ fecunda is to reduce recruitment, so the two 

 species may be able to coexist (Lesica and Shelly, submitted) . On the other 



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