Almost all of the parental care behaviors and mating systems seen in the Cichlidae, a family noted for its diversity in these characters, are present in the subfamily Geophaginae. Sequences of two mitochondrial genes (cytochrome oxidase II and one other) will be determined for geophagine species and outgroup representatives, and used to derive a phylogeny. With the phylogeny, the following questions will be addressed: 1) In what sequence do the varied parental care behaviors evolve and how evolutionarily labile are they? 2) Do particular modes of parental care precede particular mating systems or vice-versa? 3) Do novel behavioral traits always precede the evolution of related morphological characters? 4) How does the area cladogram for geophagines compare to those of other neotropical fish groups? 5) How general among cichlids is the accelerated rate of cytochrome oxidase II gene evolution seen in Geophagus steindachneri? With this single phylogeny, questions of great interest will be answered to those working in such diverse fields as behavioral ecology, molecular and morphological evolution, fish systematics, and neotropical biogeograhy.