15 



electrophoretically (separated on 

 electrically charged gels) , and a "map" of 

 the sequence of the fragments and their size 

 is developed. These maps are then analyzed 

 by computer, and diagrams of phylogenetic 

 (evolutionary) relationships and the degree 

 of cpDNA variation can be generated. The 

 results of such studies for this Astragalus 

 complex are presented in Figures 3 and 4, pp. 

 16-17. Three populations in each state were 

 studied. The results indicate that the 

 majority of the cpDNA genetic variation is 

 partitioned between populations in different 

 states, and that there is relatively little 

 variation among populations within a single 

 state (Fig. 3). The amount of variation 

 among the states is very high (Lavin et aJL. 

 1990) , approaching levels observed between 

 full species. It was not clear from the 

 analyses of the data whether the cpDNA among 

 the three states is monophyletic (evolved 

 from a common ancestor) . The analysis in 

 Figure 4 included one additional computer 

 "step" (i.e., it was not the most 

 parsimonious analysis) , but it does suggest 

 that the populations in the three states do 

 share a common cpDNA ancestor. Most 

 significantly, the results did reveal that at 

 least the Montana (A^ molybdenus ^ and Wyoming 

 (A^ shultziorum ) populations are derived from 

 a common ancestor. 



ELECTROPHORETIC ANALYSIS OF ENZYME VARIATION: 

 This technique also Involves a study of the 

 genetic variation within and among 

 populations, but the subjects of study are 

 enzymes. Enzymes are proteins whose amino 

 acid sequences are determined by the nuclear 

 DNA (chromosomes); hence, differences between 

 the enzymes, as detected by separating them 

 on electrically charged gels, directly 

 reflect genetic differences. In this study, 

 five populations from Montana, four from 

 Wyoming, and three from Colorado were 

 examined. The results were generally 

 inconclusive, but they do suggest that the 

 populations are not highly divergent from one 

 another in terms of chromosomal genetic 

 variation. The sample size (number of 

 individuals per population) was small, 

 however, and an expanded study would be 

 needed to obtain statistically significant 



