Phylogenetic Systematics oflguanine Lizards 



131 



Iguaninae 



FIG. 51. Phylogenetic relationships within Iguaninae according to the present study. 



genera had already diverged from one another. Accepting this proposition might lead one 

 to conclude that these lineages separated during a relatively brief time interval and that they 

 have been evolving separately for a long time. Implicit in this conclusion, however, is the 

 assumption that rates of character evolution are similar in separately evolving lineages. 

 This assumption is contradicted by the distribution of derived characters among the basic 

 taxa and the relationships that can be resolved by them. For example, Amblyrhynchus 

 possesses more obvious derived characters not found in Conolophiis than does either 

 Brachylophus or Dipsosaurus, even though Conolophus apparendy shared a more recent 

 common ancestor with Amblyrhynchus than it did with either Brachylophus or 

 Dipsosaurus. Given that the characters used in this study are representative of overall 

 phenotypic evolution, one must conclude that the lineage leading to Amblyrhynchus has 

 evolved more rapidly than those leading to Brachylophus and Dipsosaurus. 



