| Abstract: | The order Rodentia contains two suborders, Hystricognathi and Sciurognathi, each of which has representatives in the Old and New Worlds. Taxa have traditionally been separated into these two suborders based upon jaw structure, masseter muscle attachment, and other morphological characters. However, the traditional classification has been recently questioned because many of the genera share characteristics of both suborders, indicating a paraphyletic relationship or alternatively, convergent evolution. In this study, DNA sequence data from the cytochrome c oxidase subunit II gene (COII) were examined for seven representative taxa in order to obtain an independent data set (non-morphological) to serve as an objective alternative to the more traditional methods. These molecular data were used to address the following phylogenetic questions: 1) Is the suborder Hystricognathi monophyletic, meaning that all species are derived from a common ancestor? 2) Are the New World rodents the result of a single radiation from the Old World, or are they a result of multiple radiations? 3) How should the genera that share characteristics between the suborders be classified? Although additional research is currently in progress, preliminary sequence data indicate that the suborder is monophyletic with the occurrance of one radiation of animals from the Old World to the New World and that Pedetes should be included in the suborder Hystricognathi. |
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