5 



site where fecundity was very low in 1989. Nonetheless, fecundity, 

 as measured by both of these statistics, was higher at the Vipond 

 Park site, and population growth was also higher at this site. The 

 percentage of plants with more than one rosette remained constant 

 at both sites. The mean number of seeds per fruit was constant at 

 Lime Gulch but decreased at Vipond Park. 



In 1989 most of Montana received above-normal precipitation in 

 late summer and early autumn, and although snowpack was light in 

 southwestern Montana during the following winter, late spring 

 precipitation was also above average. Previous to this period, 

 southwestern Montana had experienced two years of serious drought 

 conditions. Since germination of Arabis fecunda seed occurs 

 readily without any cold treatment (Lesica, unpublished data) , the 

 wet period in late summer and early autumn probably resulted in 

 high levels of recruitment and strong seedling growth. Both higher 

 than average levels of autumn and spring precipitation may have 

 contributed to the dramatic increase in fecundity. 



Generally Arabis fecunda plants do not produce fruit during 

 their first year; however, in 1990, 21% (49 of 237) of the newly 

 recorded plants at Vipond Park and 11% (11 of 151) of the newly 

 recorded plants at Lime Gulch produced fruit. We believe that this 

 phenomenon is a result of the combination of a wet fall followed by 

 a wet spring. 



