The ability to preserve existing biodiversity is best improved by a thorough understanding of the factors that cause changes in both species number (species diversity) and the variety of shapes and sizes exhibited by those species (morphological diversity). To this end, this research quantitatively examines the relationship between the rate of morphological diversification and three factors, extent of geographic range overlap among close relatives, the diversity of physical habitats occupied, and a morphological feature that increases the complexity of a functional system. This study uses groups of species within lineage of North American freshwater fishes known as darters (Teleostei: Percidae) to examine the relationship between each factor and the rate of morphological diversification. Because this study explicitly examines the relationship between geographic range overlap among close relatives and the rate of morphological diversification, the results will indicate whether current conservation methods, specifically the human-mediated establishment of populations of threatened species in new locations, actually induce morphological change rather than act to preserve a species' morphology over long periods of time. In addition, the results will not only provide information about the morphological diversification of darters, they will also suggest whether the three factors have been important in the morphological diversification of other groups of animals and plants.
