Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)


The superfamily Tyrannoidea (Aves) has been the subject of numerous systematic investigations, yet the relationships among and within the five component families remain ambiguous. Relationships within the superfamily were investigated using starch gel electrophoresis of 20 enzyme loci in 14 cotinga genera, 12 manakin genera, the flycatcher genus Myiarchus, and each of the genera from the monogeneric families Phytotomidae and Dxyruncidae. Electrophoretic characters were found to contain considerable information concerning familial and subfamilial relationships within this New World assemblage. The Fitch-Margoliash "jackknife strict consensus tree" and a cladogram generated from the character state distributions were very similar and were used in the formation of a revised classification. The new classification contains several radical departures from the commonly accepted arrangement, most notably the division of the Cotingidae into four separate lineages.The results disagree with several portions of a phylogeny derived from a study of DNA/DNA hybridization (Sibley and Ahlquist 1985). The implications of this finding are discussed. Phylogenetic trees, derived from distance measures, may be of variable reliability due to variance in the quality of the data sets from which they are produced. Such trees are therefore of questionable value as a means of summarizing large data sets. To improve our confidence in these trees, a jackknife technique for data manipulation is presented that, in combination with existing consensus techniques, identifies those portions of evolutionary history that are poorly known due to inconsistencies in the data. Such trees more accurately represent the results of a study than do current tree-generating algorithms that obscure areas of uncertainty. The approach is a simple modification of existing tree-generating methods. As an illustration, a biochemical data set is analyzed using this technique.