Scientists have long been interested in the factors responsible for the evolution of differences in the sexes. Knowledge of such mechanisms of evolution within species also provides insight into the divergence of species which in turn contributes to our understanding of the diversification of life. This project will study the evolution of sex differences in chaenopsid fishes, a group of tropical marine blennioid fishes. Prior research on the genus Coralliozetus has revealed that many of the differences in males and females evolved in a single event in which the development of females became truncated. Similar changes in the timing of development are known for other organisms, yet have rarely been implicated in the divergence of the sexes. The precise developmental mechanisms responsible for this divergence, whether a slowing or an early cessation of development in females, will be determined by describing the development in both sexes of these and related species. The role of this morphological change in the ecology of these fishes will be studied by testing a hypothesized behavioral shift in habitat use of females. Habitat shifts by one sex are poorly documented and represent an important, but recently overlooked, cause for the evolution of sex differences. The generality of these results will be tested in a similar study on the equally dimorphic chaenopsid genus Emblemaria. This research is unique in integrating systematics, developmental biology and behavioral ecology in the study of sex differences.
