creek population (EO#008) had higher 

 recruitment, faster growth, and higher 

 mortality. Annual fecundity was higher and 

 plants became fecund at an earlier age. 

 Population size was more stable at Charleys 

 Gulch than at Canyon Creek (Lesica and Shelly 

 1994). Walsh (1992) found that larger _ plants 

 were more likely to survive and more likely 

 to have higher reproductive rates. 



The frequency of bolting was much higher at 

 Canyon Creek, and this is likely the source 

 of much of the difference between Arabis 

 fecunda life histories at the two sites 

 (Lesica and Shelly 1994). Bolting plants 

 have higher annual fecundity and much higher 

 mortality than axillary flowering plants. 

 Axillary flowering plants are iteroparous 

 (perennial or polycarpic) , while bolting 

 plants approach the semelparous (annual or 

 monocarpic) life history (Lesica and Shelly 

 1994) . Walsh (1992) also found that bolting 

 plants are more likely to die. 



POPULATION GENETICS: The differences in life 

 history traits exhibited among the Arabis 

 fecunda populations studied could be the 

 result of genetic differentiation, phenotypic 

 plasticity (one genotype that produces 

 different phenotypes under different 

 conditions) or both. Quantitative genetics 

 studies are required to determine the basis 

 of the variation. Leeper et al. (in press) 

 used starch gel electrophoresis to 

 investigate apportionment of genetic 

 variation in Arabis fecunda populations. Of 

 18 putative loci scored, 17 were invariant; 

 however, the one polymorphic locus had 

 different frequencies among the populations, 

 suggesting a degree of differentiation. 

 Results of germination studies (Lesica and 

 Shelly 1994) indicate that there is genetic 

 differentiation between the Charleys Gulch 

 and Canyon Creek populations. Furthermore, 

 they suggest that there is a genetic 

 difference between plants that bolt and those 

 that do not. Together these results provide 

 evidence that differences in life history 

 traits between the two sites have a genetic 

 basis (Lesica and Shelly 1994). 



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