PHYLOGENETIC CONCLUSIONS 



PREFERRED HYPOTHESIS OF RELATIONSHIPS 



Figure 51 summarizes my conclusions about phylogenetic relationships among the genera 

 of iguanine lizards, based on the two analyses discussed above as well as a consideration 

 of variation within basic taxa. Synapomorphies of the various taxa are given in the 

 Diagnoses section, below. Although this is not the most fully resolved cladogram that can 

 be obtained from the characters used in this study, it indicates the best-supported 

 monophyletic groups. The differences between this cladogram and the most fully resolved 

 cladogram that can be obtained from these data are as follows: (1) Either Brachylophus or 

 Dipsosaurus can be considered the sister group of all other iguanines on a fully resolved 

 cladogram. Since both hypotheses are equally reasonable in terms of the characters 

 discussed here, I leave the relationships among Brachylophus, Dipsosaurus, and the 

 monophyletic group composed of all other iguanines unresolved. (2) Although it is 

 possible to place Ctenosaura as the sister group of the clade composed of Iguana and 

 Cyclura, this conclusion is based on one of two possible interpretations of a single 

 character, and this character must later be lost within the clade that it is supposed to 

 diagnose. I prefer to leave the relationships of Ctenosaura to Sauromalus, Iguana and 

 Cyclura, and Amblyrhynchus and Conolophus unresolved. (3) Finally, a fully resolved 

 cladogram places Sauromalus as the sister group of the Galapagos iguanas, while I leave 

 the relationships of Sauromalus to Ctenosaura, the Galapagos iguanas, and Iguana and 

 Cyclura unresolved. The reasons for these differences are discussed more fully in the 

 sections on phylogenetic analysis, above, and the diagnoses of the monophyletic groups of 

 iguanines, below. 



CHARACTER EVOLUTION WITHIN IGUANINAE 



Although the primary goal of this study was to determine the relationships among the 

 genera of iguanine lizards, I was only partially successful in this endeavor. Other than 

 Iguaninae as a whole, I recognize only three monophyletic groups composed of more than 

 one of the basic taxa, whereas a fully resolved dichotomously branching phylogeny would 

 have six such groups. Failure to resolve relationships cannot be attributed to a lack of 

 morphological variation within Iguaninae, for derived characters-which are sometimes 

 numerous- support the monophyly of each of the basic taxa. Therefore, it seems that most 

 of the character evolution within iguanines occurred after the lineages leading to the extant 



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