The phylogenetic relationships among the orders of otophysan fishes and the families of catfishes will be investigated using nucleotide sequence variation of ribosomal RNA. Ribosomal RNA sequences will be obtained using a primer-extension sequencing method applied directly to RNA samples isolated from tissue samples. Statistical tests will be applied to these data to resolve alternative hypotheses previously generated from morphological data. The evolutionary events underlying the multiple derivations of complex morphological systems such as the elastic spring apparatus and palatine-maxillary mechanism will be evaluated in the context of a molecular phylogeny. The resulting molecular phylogenies will also be used to test predictions of the vicariance and dispersalist models of vertebrate radiation and to reevaluate major trends of morphological evolution among otophysan fishes. The phylogenetic information contained in different parts of the ribosome will be examined to identify a general range of divergence times over which ribosomal sequence variation is likely to be informative for teleost fishes.
