INTRODUCTION TO BIOCHEMICAL SYSTEMATICS 



61 



Throckmorton studied the pteridines of 156 species representing five 

 sub-genera. Estimations of pteridine content were made visually from 

 paper chromatograms of extracts. Their results indicated that primi- 

 tive species from each sub-genus contained greater amounts of 

 several pteridines in the body than did the more highly evolved 

 forms. Even some of the colorless pteridines were reduced in amount 

 in certain highly evolved forms. Notably, drosopterine and sepiapteri- 

 dine have been almost eliminated in the testes of advanced forms of 

 each evolutionary line, and the authors suggest that there is evidence 

 that different mechanisms have arisen to bring about this decrease 

 among the various evolutionary lines. It is obvious that this system 

 offers an additional valuable key to Drosophila phylogeny with no 

 indication presented that it contradicts or challenges the system 

 established from genetic and cytological or morphological criteria. 



Another interesting approach to comparative biochemistry 

 with an essentially phylogenetic focus is represented by the work 

 of Vogel (1959a, 1959b, 1960, 1961) on lysine synthesis. It has been 

 known for some time (see Wagner and Mitchell, 1955, p. 203) that the 

 biosynthesis of lysine proceeds via two different pathways involving 

 either a-aminoadipic acid (in Neurospora) or diaminopimelic acid (in 

 E. coli). 



Vogel extended this knowledge to numerous plants represent- 

 ing various major taxonomic groups including bacteria, algae, fungi, 

 and vascular plants. The results of his investigations are summarized 

 in the table below (Table 4-2). Vogel utilized a technique involving 

 radioactive tracers in which the labelling pattern of lysine was indica- 

 tive of the pathway by which it was formed. 



Conclusions from these data are that, by the criterion of com- 



