There is widespread agreement that increasing levels of 

 atmospheric carbon dioxide and other "greenhouse gases" will 

 result in global warming and widespread alteration of rainfall 

 patterns during the next 50 years (Peters 1988, Henderson-Sellers 

 1990) . Drier conditions are expected to cause a decrease in 

 recruitment and an increase in mortality in Arabis fecunda 

 populations. Warmer winters may result in some increase in 

 fecundity and may partially offset the effects of drier 

 conditions on mortality and recruitment. Nonetheless, if winter 

 precipitation in southwest Montana decreases, populations of A. 

 fecunda may decline. The greenhouse effect is also predicted to 

 cause an increase in the variation of weather events (Schneider 

 et al. 1992). Increased environmental variation could interact 

 with the high demographic variation of some A^ fecunda 

 populations to increase the chances of extinction. 



In summary, many populations of Arabis fecunda from a 

 variety of habitats should be given protection to ensure 

 maintenance of genetic diversity. Small populations that 

 demonstrate widely fluctuating demographic behavior are less 

 appropriate for long-term conservation purposes. Populations in 

 relatively mesic habitats are expected to have longer persistence 

 and should be given priority over those in drier sites. 



ACKNOWLEDGEMENTS 



Lisa Schassberger Roe, Peter Achuff and Bonnie Heidel helped 

 conduct field work. Portions of this study were funded by 

 Beaverhead National Forest, the U.S. Fish and Wildlife Service 

 and The Nature Conservancy. 



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