Research Interests and Goals – Dr. Steven L. Powers

My primary research interest is the evolution of stream fishes of the southeastern United States and the ecological and historical variables that have influenced and continue to influence them. Not only are fishes inherently interesting due to their high level of diversity, range of evolutionary novelties, and varied ecologies, they are also excellent model organisms for investigating evolutionary process. For many fishes, confinement to small streams and low dispersal capability provides a natural setting for investigating modes of speciation and biogeographic patterns. Dramatic sexual dimorphism present in several groups of fishes also indicates that sexual selection has played a major role in their evolution. Furthermore, the physical pressures of living in stream habitats have influenced the evolution of stream fishes and the communities to which they belong. My research has studied and continues to study evolution, conservation genetics, molecular and morphological systematics, biogeography, and ecology of freshwater fishes of the southeastern United States. To address such a wide variety of topics, I have employed many techniques, including assessments of genetic differentiation, molecular and morphological phylogenetic systematics, quantifying stream habitat and community structure, forming and testing biogeographic hypotheses, and quantifying life history characteristics.

Regardless of questions being investigated or techniques being used, it is imperative to have a strong working knowledge of the study organisms, an understanding of the processes influencing them, and an awareness of the strengths and limitations of investigative techniques. Without this understanding, problems can arise in forming hypotheses and interpreting results of evolutionary studies. By working in similar systems, with similar species, I gain a more solid foundation from which to build hypotheses about the processes influencing the evolution of my study organisms. These hypotheses can then be tested and modified by continual addition of data and further analyses. By developing more accurate hypotheses of the evolutionary history of taxa, I am able to develop more refined hypotheses of evolutionary and biogeographic processes. This leads to reciprocal illumination of evolutionary questions and forms a cornerstone of my research program. This understanding and philosophy is one that I have formed partly through my own experiences and partly through working with my doctorate advisor, Dr. Richard Mayden. As a mentor to future scientists, I plan to pass along this philosophy and encourage my students to incorporate their own experiences and ideas in developing research goals much as Dr. Mayden did with me.

The future of my research program will continue to focus on the evolution of stream fishes of the southeastern United States. Several projects that I have worked on or are currently working on have resulted in data sets that raise very interesting questions about the role of population size in evolution. Of particular interest is the opportunity to test Coalescent Theory using DNA sequence data from fishes throughout the Cumberland and Tennessee River drainages of Kentucky, Virginia, North Carolina, Georgia, Tennessee, and Alabama. Preliminary data from two species complexes with similar biogeographic patterns but contrasting population sizes within these drainages suggest that time to coalescence is indeed determined largely by population size. The implications of Coalescent Theory on our understanding of diverse, recently evolved lineages with large population sizes are profound. The roles of population ecology and biogeography will become even more important in studies of evolution and speciation with increased understanding of the influence of population size on evolution. This line of investigation will be a central theme of my research program for many years as I plan to continue adding data from other species inhabiting the Cumberland and Tennessee drainages. This will allow for a wide range of projects for potential graduate students and extramural funding from many organizations.